Electrochem doi: 10.3390/electrochem7020016

Authors: Oleg Kozaderov Frol Vdovenkov Pavel Tarakanov

The morphological and structural state of rough solid electrodes usually has a complex effect on the kinetics of an electrochemical process. In order to correctly distinguish the influence of different factors on the rate of an electrode reaction, it is necessary to first separate a purely geometric current rise caused by the surface area increase. At the same time, it is necessary to take into account that surface roughness itself often not only leads to a geometric rise in the electrode area, but also contributes to a change in the kinetic parameters of the electrochemical process. As a consequence, the conclusion regarding an electrocatalytic effect will be reasonable only if the roughness effect is correctly taken into account. The most difficult problem is to establish the role of roughness when experimental electrochemical data are obtained under mixed diffusion–kinetic control of the electrode process. However, the use of appropriate theoretical approaches is required to correctly determine the kinetic characteristics of the electrochemical stage, i.e., of the charge transfer stage. This paper establishes the influence of the morphology and structure of electrodeposited copper coatings on the kinetics of the cathodic reduction of nitrate ion, which occurs in a mixed diffusion–kinetic mode, using the theoretical model of chronoamperometry of an electrochemical process on a rough electrode developed earlier by the authors. Several Cu-electrodes with roughness and structure, the parameters of which vary widely enough, were obtained by cathodic deposition from sulfate solutions of different compositions. The integral (roughness factor) and local (average roughness) characteristics of the surface morphology were determined by methods of underpotential deposition and atomic force microscopy, respectively. Structural investigation of the electrodeposited coatings was carried out by X-ray diffraction to determine their crystallographic structure and average crystallite size. The methods of voltammetry and a rotating disk electrode revealed the mixed kinetics of the electroreduction of NO3− ions. The kinetic parameters of the charge transfer stage on the copper coatings with a roughness factor of fr ≤ 3.5 are determined for the first time in this paper by treatment of the experimental current decay curves with the non-linear theoretical equation obtained by the authors for the chronoamperogram of the process on rough electrodes. It was found that the rate constant of the charge transfer stage and the exchange current density of the nitrate ion electroreduction increase by about 50%, with an increase in the average surface roughness from 25 to 120 nm. Considering that this effect is not caused by a purely geometric increase in the true surface area of the electrode, and that the average crystallite size is approximately the same (25 ± 2 nm) for all investigated coatings, it can be concluded that the electrocatalytic activity of copper increases in the reaction of the cathodic reduction of nitrate ions during the transition to copper electrodes with the higher average surface roughness. Taking into account XRD data, the role of the structural and morphological state in the kinetics of the electroreduction of nitrate ions has been established. The smoothest polycrystalline coating was found to be the least electrocatalytically active in this reaction. On the contrary, the roughest coatings with the most prominent plane (220) show the highest activity, which increases with increasing average roughness, possibly due to the growth of defects and excess energy of such curved surfaces.

Electrochem doi: 10.3390/electrochem7020015

Authors: Rudyere Nascimento Silva Giuseppe Abíola Camara Leandro Aparecido Pocrifka Raimundo Ribeiro Passos

The development of efficient catalysts for the glycerol oxidation reaction (GOR) is crucial for advancing direct glycerol fuel cells. This study provides mechanistic insights into the glycerol electro-oxidation reaction (GOR) on Co@Pt/C, Ni@Pt/C, and Sn@Pt/C catalysts using in situ FTIR spectroscopy. While the structural and electrochemical properties of these materials have been previously reported, their reaction pathways and product selectivity under alkaline conditions remain unclear. Electrochemical performance was evaluated through cyclic voltammetry (CV) and chronoamperometry (1.0 M KOH + 1.0 M glycerol), revealing that the bimetallic catalysts exhibited superior catalytic activity compared to Pt/C. Co@Pt/C demonstrated the highest performance, with a 7.5-fold increase in current density relative to Pt/C, followed by Sn@Pt/C (3.4-fold) and Ni@Pt/C (2.8-fold). In situ FTIR analysis identified key oxidation products, including C3, C2, and C1 species, with evidence of both partial and complete oxidation. These findings demonstrate that the core metal plays a key role in governing reaction pathways and C–C bond cleavage, providing important insights for the rational design of anode materials in direct glycerol fuel cells.

Electrochem doi: 10.3390/electrochem7020014

Authors: Muhammad Javed Iqbal Li-Wei Tseng Fa-Cheng Su Qaiser Abbas Hsiharng Yang

Direct ammonia fuel cells (DAFCs) offer a promising pathway for carbon-free energy conversion but their practical performance is limited by sluggish cathode kinetics. In this work, non-precious FeCoN catalysts offer a cost-effective solution, yet carbon support optimization is crucial for activity and stability. FeCoN/XC-72R, FeCoN/CNT, and FeCoN/CNH cathode catalysts were synthesized by annealing at 550–750 °C. Their structure and morphology were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical behavior was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in alkaline medium containing KOH and NH4OH. FeCoN/XC-72R exhibited the lowest resistance of 27 Ω and superior activity. In single cell tests using a 40 wt% PtIr/C anode catalyst at 2 mg cm−2, the FeCoN/XC-72R catalyst achieved the highest power density of 71 mW/cm2 under optimized conditions of 0.1M NH4OH + 3M KOH, 100 °C, and O2 feed. Among the carbon supports, carbon black (XC-72R) proved the most effective support for FeCoN catalysts in low concentration DAFCs, outperforming carbon nanotubes (CNTs) and carbon nanohorns (CNHs). These findings highlight the importance of carbon support selection in the design of efficient cathodes for next generation low concentration direct ammonia fuel cells.

Electrochem doi: 10.3390/electrochem7020013

Authors: Soumya Kollipara Edan Fields Seiichiro Higashiya Latika S. Chaudhary Haralabos Efstathiadis

Understanding lithium distribution and transport within Li-ion battery components is critical in improving battery longevity, safety and performance. This study investigates lithium concentration profiles across the interface of an aluminum-doped Li7La3Zr2O12 (Al-LLZO) solid electrolyte and a lithium metal anode using Nuclear Reaction Analysis (NRA), a non-destructive depth-profiling technique. The Al-LLZO electrolyte was synthesized via electrospinning, producing nanofibers, which were subsequently sintered into pellets of average thickness 380 µm. These pellets were integrated into a Li|Al-LLZO|NMC-111 half-cell and cycled at 0.1 C for 1, 3, and 10 cycles, indicating pronounced lithium accumulation at the electrolyte–anode interface. Using NRA, this study provided a clear pathway for better understanding lithium transport and interfacial behavior, by quantitatively measuring the lithium distribution at the Al-LLZO electrolyte–electrode interface, and to look at the changes at this interface over the battery cycles.

Electrochem doi: 10.3390/electrochem7020012

Authors: Zineb Hammi El Houceine Benhadria Soraya Lakhloufi Mohamed Amine Koumaiti Lamyaa Merbouh Najoua Labjar El Mostapha Lotfi Hamid Nasrellah Ayoub Cherrat Souad El Hajjaji

Cost-effective, durable, and environmentally friendly electrocatalysts to be used for the alkaline hydrogen evolution reaction (HER) represent one of the key challenges facing green hydrogen generation. In this context, a TiO2-doped hydrochar derived from Phoenix dactylifera L. Deglet Nour (date pits) was synthesized and incorporated into a graphite-based electrode to improve HER performance in a 1 M KOH solution. Three TiO2 loadings (1, 3, and 6 wt%) were systematically studied and compared using electrochemical techniques to evaluate the influence of oxide incorporation on HER kinetics. In parallel, physicochemical characterization analyses were performed to acquire an in-depth understanding of the morphology, composition, and surface properties of biomass-derived carbonaceous materials and to establish correlations with their electrochemical behavior. The G/HC-3% TiO2 electrode exhibited the most pronounced electrocatalytic performance, with an overpotential of 194 mV at −10 mA·cm−2 and a Tafel slope of 67 mV·dec−1, indicating favorable interfacial charge transfer kinetics. The present work demonstrates that biomass-derived TiO2-doped hydrochar has significant potential as a sustainable and high-performance electrocatalyst in alkaline water electrolysis.

Electrochem doi: 10.3390/electrochem7020011

Authors: Wei Zhang Hangxuan Xie Zirui Dou Zhentao Hao Qianhui Huang Ziqi Guo Chao Wang Kanghua Miao Xiongwu Kang

The authors would like to make the following corrections about the published paper [...]

Electrochem doi: 10.3390/electrochem7020010

Authors: Tingting Han Tao Song Junyu Gan Dongxue Han Li Niu

This study proposed an effective capacitance (Cec) for bare and conducting polymer-covered electrodes using electrochemical impedance spectroscopy (EIS). Bare electrodes show three regimes: potential-dependent Helmholtz capacitance, Gouy–Chapman–Stern diffusion capacitance (1 MHz–10 Hz), and complex low-frequency responses, deviating from semi-infinite Warburg diffusion (1 Hz–10 mHz). Polyaniline (PANI) and poly(3,4-ethylenedioxythiophene) PEDOT-based electrodes exhibit larger potential-dependent diffusion pseudocapacitance (1 MHz–10 Hz) and the absence of a Warburg tail or a nearly horizontal low-frequency slope at 0.01–0.026 (1 Hz–10 mHz). A high-frequency Cec of a PANI membrane correlates with bulk electrolyte concentration, while bare electrodes are less affected and dominated by Helmholtz capacitance. The equivalent circuit of the time-dependent EIS impedance spectrum for bare electrodes and PANI and PEDOT-based electrodes shows parallel capacitor behavior in combination with high-frequency capacitance (1 MHz–10 Hz) and a low-frequency response (1 Hz–10 mHz). The mathematical simulation of effective capacitance Cec with respect to time period t (f−1) follows two time constants (τ = RC), representing double-layer capacitance or pseudocapacitance (τ1) and complex low-frequency responses or Warburg diffusion (τ2) for bare electrodes and conducting polymer-based electrodes, respectively. This simulation analysis also elucidates the frequency dependence of the Warburg characteristic frequency (ω) and the extension of the double-layer capacitance diffuse distance LD for H+ with GC electrodes to approximately 7.37–15.15 μm over a time interval of ca. 1 s (t = f−1). The diffusion coefficient Di of K+ ion transfer through a PEDOT solid contact from 1 mC (0.1 µm) to 10 mC (1 µm) is in the range of 0.57–12 × 10−10 cm2·s−1, following a power law with an exponent of 1.75 with respect to the polymerization time of PEDOT, which is inconsistent with Fick’s law.

Electrochem doi: 10.3390/electrochem7020009

Authors: Phan Khanh Thinh Nguyen Thi Thu Ha Tran Tamirat Redae Gebreselassie

Direct urea–hydrogen peroxide fuel cells (DUHPFCs) are promising for sustainable power generation, but their performance is governed by highly nonlinear material and operating interactions. This study develops a machine-learning framework employing a multi-output artificial neural network (ANN) to predict cell voltage, power density (PD), and substrate-based energy efficiency (SEE) of DUHPFCs. The ANN exhibits excellent predictive accuracy, achieving coefficients of determination (R2) above 0.995 and normalized root mean square errors (NRMSE) below 1.75 × 10−2 for all outputs. Model interpretability is enhanced by using Shapley additive explanations and partial dependence plots, which identify current density as the dominant factor affecting DUHPFC performance, followed by temperature and anolyte composition. The ANN is coupled with a multi-objective Pareto-search algorithm optimization (PAO) to resolve the trade-offs among competing performance metrics. Under different optimization objectives, a DUHPFC with an Ni0.2Co0.8/Ni-foam anode is predicted to achieve a maximum PD of 45.6 mW/cm2 with a low SEE of 2.6% or a maximum SEE of 15.2% with a moderate PD of 40.9 mW/cm2. Additionally, a balanced operating regime is identified, achieving a PD of 43.1 mW/cm2 and an SEE of 13.9%. Overall, the proposed framework provides an effective decision-support tool for optimizing DUHPFC performance under competing objectives.

Electrochem doi: 10.3390/electrochem7020008

Authors: Dionysios S. Karousos Panagiotis Priftis Mirtat Bouroushian

CdSe-coated electrodes, formed by electrodeposition of CdSe barrier layers on metallic Ti or porous TiO2 substrates, were characterized by electrochemical impedance spectroscopy in a (photo)cell using aqueous redox electrolytes based on the sulfide/polysulfide or ferro/ferricyanide couples. The influence of electrode material properties, electrolyte contact, thermal annealing, and measurement conditions (illumination, frequency, potential-scan speed) on the shape and features of Mott–Schottky plots was investigated. The obtained information was evaluated on the basis of the ideal Schottky diode model and photocurrent voltammetry data. Deviations from linear diode behavior and uncertainties in the determination of energetic parameters were examined and attributed to the presence of donor density gradients and surface states in the semiconductor electrode, further complicated by chemical corrosion. The origin of the observed non-idealities is inquired, and specific aspects of the measuring procedure related to the non-stationary character of the interface are discussed.

Electrochem doi: 10.3390/electrochem7020007

Authors: Cheng-Xuan Xiao Chun-Gu Liu Cao-Feng Chen Ping-Feng Yang Jen-Kuang Fang Hou-Chien Chang

This study investigates the non-uniformity (NU%) of copper deposition in a three-dimensional panel electroplating cell using COMSOL Multiphysics® 6.1 (COMSOL Inc., Burlington, MA, USA). To ensure the accuracy of the simulated current efficiency, the modeling was initially conducted on the electrodeposition of nanoscale metal wires (Nanowires, NWs) using the Finite Element Method (FEM) in COMSOL. After verifying that the simulation accurately reflected the current efficiency at the nanoscale, the model was scaled up to simulate full-sized panel-level electroplating. Various simulation conditions were explored, including two dimensional and three dimensional, electrode kinetics equations, electrolyte compositions, and current densities. The effects of these parameters on current efficiency and deposition uniformity were analyzed to develop a highly accurate COMSOL model. In terms of electrode kinetics, the study compares the advantages and limitations of secondary current distribution and tertiary current distribution models found in the previous literature, and evaluates their simulation results. Furthermore, to reflect the experimental condition where a pre-deposited copper seed layer was applied to reduce internal cathode resistance, the electrode shell physics module in COMSOL was implemented to simulate the potential distribution across the cathode surface. The results confirm that the numerical model using the tertiary current distribution provides more accurate predictions compared to the conventional secondary current distribution approach.

Electrochem doi: 10.3390/electrochem7010006

Authors: Kassapa U. Gamagedara Dipankar Roy

Molybdenum (Mo) is currently considered as a potential diffusion barrier material for copper (Cu) interconnects, and these interconnect structures are generally processed using the technique of chemical mechanical planarization (CMP). While a limited number of publications on Mo CMP are presently available, the considerations for mitigating CMP-induced galvanic corrosion of Mo have remained largely underexplored. Using a model CMP system in pH-neutral slurries of citric acid with silica abrasives, the present work demonstrates how Mo barrier lines in contact with Cu wires in the CMP environment can develop CMP defects of galvanic corrosion. Including imidazole in the slurry considerably reduces the galvanic current of this corrosion process. The mechanisms of galvanic inhibition and material removal are examined by employing strategic tribo-electrochemical measurements. Open-circuit potential and potentiodynamic polarization measurements performed under surface abrasion aid the characterization of CMP-enabling surface reactions. The slurry’s surface chemistry initiates the primary modes of material wear for CMP, and corrosion-induced propagation of subsurface wear mostly governs the measured material removal rates for both Mo and Cu. Although the Cu:Mo selectivity of material removal is affected as the galvanic corrosion of Mo is suppressed, this effect can be controlled by varying the slurry content of imidazole.

Electrochem doi: 10.3390/electrochem7010005

Authors: Pablo Fernandez Marisé García-Batlle Bo Shang Hailiang Wang Gregory N. Parsons James F. Cahoon Rene Lopez

Effective electrochemical CO2 reduction to liquid fuels requires that the local catalytic environment facilitates the desired reactivity, yet a microscopic understanding of this environment is difficult to achieve from experiment alone. In this work, a 3D reaction-diffusion model was developed to explore the effects of electrode surface area and local geometry on the performance of a heterogeneous catalyst that performs a two-step CO2 reduction cascade reaction to CO and then CH3OH under aqueous conditions. Kinetic parameters for the model were inspired by experimental results using a cobalt phthalocyanine (CoPc) catalyst. Three-dimensional architectures composed of arrays of square pillars with varying dimensions and either smooth or periodically modulated surfaces were tested, revealing the extent to which geometry modulates the performance of the cascade reactions. Although structural variations modulate local concentration gradients, we find that electrochemically active surface area predominantly governs the overall cascade reaction. Moreover, the results suggest that supersaturation of CO, with concentrations up to ten-fold higher than the equilibrium solubility limit, might be critical for more efficient conversion to CH3OH. For any given geometry, the spatially averaged ratio of [CO] to [CO2] is dictated by the electrochemically active surface area and determines the yield of CH3OH. For a fixed surface area, geometries that spatially confine the electrolyte yield moderate local [CO] to [CO2] ratios within small volumes. In contrast, less confining geometries result in a broader distribution of local ratios spread over larger volumes, with both configurations yielding the same spatially averaged [CO] to [CO2] ratio. These insights provide valuable design principles—highlighting the critical importance of surface area and possibly CO supersaturation—for engineering advanced electrode architectures that leverage intermediate trapping and CO supersaturation to enhance overall performance in tandem CO2 reduction systems.

Electrochem doi: 10.3390/electrochem7010004

Authors: Andrei Pligovka Sergey Zavadski Andrei Lazavenka Vadim Bogush

The high reactivity of lanthanide metals poses a challenge to the electrochemical anodizing of surfaces for nanostructured coatings. This paper presents the first systematic experimental investigation of anodic oxidation of lanthanide gadolinium in aqueous solutions of citric, boric, oxalic, and tartaric acids. The voltage-current-time responses of anodizing of gadolinium, Al/Gd and Al/Nb/Gd systems were investigated. Anodic thin films were characterized using modern analysis techniques: SEM, FIB, and EDX. Morphology and voltage-current-time response analysis of anodized Al/Nb/Gd systems made it possible to establish the niobia cork-like effect and to develop a growth model.

Electrochem doi: 10.3390/electrochem7010003

Authors: Maksym Bichev Denis Miroshnichenko Sergey Nesterenko Leonid Bannikov Leonid Saienko Volodymyr Tertychnyi Vladislav Reivi Kyrylo Serkiz Mariia Shved

It has been demonstrated that a monomolecular surface film with semiconducting characteristics forms on an austenitic, corrosion- and heat-resistant chromium–nickel steel with 0.10 wt.% C, 20 wt.% Cr, 9 wt.% Ni, and 6 wt.% Mn (10Kh20N9G6), microalloyed with yttrium, in aqueous 1 M H2SO4. This passive layer exhibits semiconducting behavior, as confirmed by electrochemical impedance and capacitance measurements. For the first time, key electronic parameters, including the flat-band potential, the thickness of the semiconductor layer, and the Fermi energy, have been determined from experimental Mott–Schottky plots obtained for the interphase boundary between the yttrium-microalloyed austenitic Cr–Ni steel (10Kh20N9G6) and aqueous 1 M H2SO4. The results reveal a systematic shift in the flat-band potential toward more negative values with increasing yttrium content in the alloy, indicating a modification of the electronic structure of the passive film. Simultaneously, a decrease in the Fermi energy is observed, suggesting an increase in the work function of the metal surface due to the presence of yttrium. These findings contribute to a deeper understanding of passivation mechanisms in yttrium-containing stainless steels. The formation of a semiconducting passive film is essential for enhancing the electrochemical stability of stainless steels, and the role of rare-earth microalloying elements, such as yttrium, in this process is of both fundamental and practical interest.

Electrochem doi: 10.3390/electrochem7010002

Authors: Eva Alonso-Muñoz Janwa El Maiss Wejdene Gongi Divya Balakrishnan Delphine Faye Karine Mougin César Pascual García

Electrolyte degradation and trace water contamination critically affect the lifetime and safety of lithium-ion batteries. In organic-based electrolytes such as acetonitrile (MeCN), even small amounts of water can trigger PF6− hydrolysis, producing HF, POF3, and related species that contribute to electrolyte ageing and alter interfacial reactions. This study explores the electrochemical signatures of ageing and moisture contamination in Bu4NPF6- and LiPF6-based MeCN electrolytes through a systematic cyclic voltammetry protocol. Platinum electrodes with different surface morphologies—flat, Nafion-coated, and nanostructured—were compared to assess their sensitivity to water-induced degradation. Cathodic Faradaic currents appearing around −0.7 to −1.0 V vs. Ag/AgCl were attributed to the protonic species generated by PF6−-induced hydrolysis. The presence of LiPF6, commonly used in battery electrolytes, further increases the concentration of anions responsible for the protonic species, therefore contributing to the acceleration of the electrolyte degradation. Experiments using a Nafion proton-conductive membrane assess the protonic origin of these peaks. Meanwhile, nanostructured platinum exhibits approximately four times higher current responses and enhanced sensitivity to water additions, reflecting the influence of surface roughness and active area. Overall, the findings indicate that electrode morphology significantly influences the detectability of ageing- and water-driven reactions, supporting the potential of nanostructured Pt as a diagnostic material for in situ monitoring.

Electrochem doi: 10.3390/electrochem7010001

Authors: Andriono Manalu Moraida Hasanah Winfrontstein Naibaho Mario Geraldi Simanjuntak Maren Sius Girsang

In this study, Ni/Mn-doped cobalt–reduced graphene oxide (Co-RGO) composites were successfully synthesized as advanced electrode materials for supercapacitors. The structural and morphological properties of the composites were characterized using FTIR, XRD, SEM, TEM, and UV–Vis spectroscopy. Their electrochemical performance was evaluated through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD). Among the prepared samples, Co-RGO doped with Ni/Mn at a 40:10 ratio exhibited the most outstanding capacitive behavior, achieving a specific capacitance of 7414 F g−1 at a current density of 10 A g−1, along with a high energy density of 565 Wh kg−1 and a power density of 4998 W kg−1. The high capacitance arises from faradaic pseudocapacitive reactions rather than electric double-layer capacitance, eliminating the need for a large surface area. These results confirm that Ni doping significantly enhances pseudocapacitance and conductivity in the Co-RGO matrix, making Ni/Mn (40:10)–Co-RGO a potential material for advanced energy storage systems.

Electrochem doi: 10.3390/electrochem6040045

Authors: Mohamed A. El-Hameed Mahmoud M. Elkholy Mahfouz Saeed Adnan Kabbani Essa Al-Hajri Mohammed Jufaili

Accurate modeling of proton exchange membrane fuel cells (PEMFCs) is essential for predicting system performance under diverse operating conditions. This study introduces a refined semi-empirical modeling that combines experimental validation with an enhanced parameter estimation method based on the Cloud Drift Optimization (CDO) algorithm. The approach focuses on identifying seven key parameters of the nonlinear PEMFC model by minimizing the difference between experimentally measured and simulated cell voltages. To assess its effectiveness, the proposed CDO-based estimator was compared with several established metaheuristic algorithms, including the particle swarm optimizer and the tetragonula carbonaria optimization algorithm. The evaluation was performed using three commercial PEMFC stacks rated at 250 W, 500 W, and the NedStack PS6, as well as experimental data obtained from the Renewable Energy Laboratory at A’Sharqiyah University. Results demonstrate that the CDO algorithm consistently produced the lowest sum of squared errors (SSE) of 1.0337 and exhibited stable convergence across multiple independent runs with a standard deviation of 1.2114 × 10−7. Its reliable performance under both normal and degraded conditions confirms the algorithm’s robustness and adaptability, establishing CDO as an efficient and dependable technique for PEMFC modeling and parameter identification.

Electrochem doi: 10.3390/electrochem6040044

Authors: Raj Shah Kate Marussich Vikram Mittal

As demand for high-performance energy storage grows across grid and mobility sectors, multivalent ion batteries (MVIBs) have emerged as promising alternatives to lithium-based systems due to their potential for higher volumetric energy density and material abundance. This review comprehensively examines recent breakthroughs in magnesium, zinc, aluminum, and calcium-based battery chemistries, with a focus on overcoming barriers related to slow ion transport, limited reversibility, and electrode degradation. Advances in aqueous and non-aqueous electrolyte formulations, including solvation shell engineering, interfacial passivation, and dual-zone ion transport, are discussed for their role in improving compatibility and cycling stability. Particular focus is placed on three high-impact innovations: solvation-optimized Mg-ion systems for improved mobility and retention, interface-engineered Zn-ion batteries enabling dendrite-free operation, and sustainable Al-ion technologies targeting grid-scale deployment with eco-friendly electrolytes and recyclable materials. Cross-cutting insights from operando characterization techniques and AI-guided materials discovery are also evaluated for their role in accelerating MVIB development. By integrating fundamental materials innovation with practical system design, multivalent ion batteries offer a compelling path toward next-generation, safer, and more sustainable energy storage platforms.

Electrochem doi: 10.3390/electrochem6040043

Authors: Wenchang Shu Fang Zhang Jun Peng Quanjun Zhang Yubao Liu Baige Sun

Yttrium–magnesium alloys are commonly employed as processing additives in magnesium alloy materials. Incorporating yttrium into magnesium alloys via Y-Mg intermediate alloys not only minimizes oxidation and burn-off loss but also simplifies operational procedures. Utilizing yttrium–magnesium alloys ensures a stable composition and reliable quality of magnesium alloy products, while contributing to reduced production costs and minimized environmental pollution. In this study, a molten salt co-reduction method was developed for the preparation Y-Mg intermediate alloys. The electrochemical co-reduction behaviors of Y(III) and Mg(II), as well as the transient states of Y-Mg intermediate alloys, were systematically investigated by transient electrochemical techniques. Results indicated that the reduction of Y(III) at the molybdenum (Mo) cathode is a reversible electrochemical process, whereas the reduction of Mg(II) is irreversible and diffusion-controlled. The diffusion coefficient of Y(III) and Mg(II) in the fluoride salt at 1000 °C were determined to be 3.98 × 10−5 cm2/s and 1.16 × 10−3 cm2/s, respectively. Electrochemical calculations revealed that the reduction of Y(III) involves a single-step transfer of three electrons, while Mg(II) involves a single-step transfer of two electrons. The corresponding electrode reactions are Y(III) + 3e−→Y and Mg(II) + 2e−→Mg, respectively. A Y-Mg alloy sample prepared by constant-current molten salt electrolysis primarily consists of the MgY phase with a composition of 88.38 wt% yttrium and 11.62 wt% magnesium.

Electrochem doi: 10.3390/electrochem6040042

Authors: O. A. González Noriega A. Flores Nicolás J. Uruchurtu Chavarín A. Torres Islas E. C. Menchaca Campos H. Martínez Valencia

In this work, plasma nitriding was carried out to improve the corrosion resistance of API 5L X70 steel. The process was conducted at different treatment times, 4, 6, 8, and 10 h, to determine which one provides greater resistance to corrosion. The conditions under which the nitriding was carried out were as follows: a mixture of 20% N2 and 80% H2 at 3 torr pressure, a current of 2.6 × 10−6 A, a voltage of 360 V, and the temperature inside the plasma chamber was 550 °C. The blank and nitrided materials were characterized using dispersive energy spectroscopy and scanning microscopy to study their morphology and chemical composition. In addition, open potential circuit, electrochemical impedance spectroscopy, and potentiodynamic polarization curves in simulated soil solution were performed to evaluate the materials’ corrosion resistance. The treatment achieved at 10 h presented the greatest corrosion resistance, reducing the corrosion current density up to three orders of magnitude. The thickness reached 678.75 µm for this condition.

Electrochem doi: 10.3390/electrochem6040041

Authors: Manuel Zulla Carolin Messerschmidt Hanadi Ghanem Johannes Bähr Lukas Hegemann Stefan Rosiwal

Nowadays, the development of efficient water treatment processes is increasingly driven by the need to provide solutions for contaminants of emerging concern. Electrochemical advanced oxidation processes (EAOPs) based on diamond electrodes can be part of innovative removal concepts. However, expensive substrates, energy-intensive chemical vapor deposition (CVD) of diamond, and market availability complicate matters for diamond electrodes to gain traction in the water treatment sector. In addition, it has to be stated that the mining and complex processing of necessary substrates like Si, Ti, Nb, or Ta need a significant amount of fresh water, which counteracts the need for more sustainability in the field of EAOPs. In this context, a ceramic-based boron-doped diamond (BDD) electrode is presented, which addresses this dilemma. The presented concept of the so-called interdigitated double diamond electrode (iDDE) consumes 14–46% less energy in batch-mode experiments to degrade an organic model molecule compared to standard BDD technology in a poorly conductive electrolyte (κ < 350 µS/cm). Laser-induced micro-structuring of the BDD layer reduces the interelectrode spacing (IES) of the iDDE to below 50 µm. The structuring approach at the micrometer scale enables the treatment of electrically low-conductivity electrolytes more energy efficiently, while reducing the need for a supporting electrolyte or a proton exchange membrane. Degradation experiments and Raman measurements reveal different properties of an iDDE compared to standard BDD technology. The iDDE concept highlights the need to understand the significance of non-uniform current density distributions on the general electrochemical activity of BDD electrodes.

Electrochem doi: 10.3390/electrochem6040040

Authors: Kepler Pyle Naz Savranoğlu Selin Naz Avdan Soha Ahmadi

Surface modification of nucleic acid-based electrochemical biosensors has been at the forefront of research since their inception. Effective modification ensures the optimization of the sensitivity, specificity, and stability of modern biosensors. Recent advances in DNA nanotechnology have enabled the development of novel electrochemical biosensor interfaces with precise assembly and high biocompatibility. In this review, we explore three strategies for enhancing biosensor performance: the integration of tetrahedral DNA nanostructures (TDNs), self-assembled monolayers (SAMs), and DNA-based hydrogels. TDNs offer well-defined geometry and controlled spatial presentation of capture probes, significantly reducing background noise and improving target accessibility. SAMs provide a robust and tunable platform for anchoring these nanostructures, enabling reproducible and chemically stable interfaces. DNA hydrogels serve as a responsive and flexible scaffold capable of signal amplification and analyte retention. These surface architectures enhance sensitivity and minimize non-specific adsorption (NSA). We discuss recent applications and experimental outcomes, highlighting how each component is driving the next generation of nucleic acid-based biosensors.

Electrochem doi: 10.3390/electrochem6040039

Authors: G. M. P. Dananjana Galappaththi Poobalasingam Abiman Poobalasuntharam Iyngaran Navaratnarajah Kuganathan

Rechargeable sodium-ion batteries (SIBs) have attracted considerable attention owing to the natural abundance and accessibility of sodium. Maricite NaMnPO4, a phosphate-based cathode material with high theoretical capacity, suffers from blocked sodium-ion diffusion channels. In this study, atomistic simulations using pair potentials and density functional theory (DFT) are employed to investigate intrinsic defect mechanisms, sodium-ion migration pathways, and the role of dopant incorporation at Na, Mn, and P sites in generating Na vacancies and interstitials. Among the intrinsic defects, the Na–Mn anti-site cluster emerges as the most favorable, exhibiting a very low formation energy of 0.12 eV, while the Na Frenkel pair (1.93 eV) is the next most stable defect, indicating that sodium diffusion is primarily facilitated by vacancy formation. Nevertheless, sodium-ion mobility in NaMnPO4 remains limited, as reflected by the relatively high migration activation energy of 1.28 eV. Among the isovalent substitutions, K is predicted to be the most favorable dopant at the Na site, whereas Ca and Cu are the most favorable at the Mn site. Thallium is identified as a promising dopant at the Mn site for generating Na vacancies that facilitate Na-ion migration, while Ge substitution at the P site is predicted to enhance the sodium content in the material.

Electrochem doi: 10.3390/electrochem6040038

Authors: Mahfouz Saeed Mohamed A. El-Hameed Essa Al-Hajri Adnan Kabbani

Proton exchange membrane fuel cells (PEMFCs) are a promising clean energy technology due to their zero gas emissions, low operating temperature, and high efficiency. This review synthesizes research from 2015–2025 on (i) materials-level approaches (advanced/modified PFSA membranes and composite membranes) that improve water retention and ionic conduction, (ii) engineered gas diffusion layers and hydrophobic/hydrophilic gradients (including Janus and asymmetric GDL architectures) that facilitate directional water transport and have been shown to increase peak power density in some reports (e.g., from ≈1.17 to ≈1.89 W·cm−2 with Janus GDL designs), (iii) flow-field design strategies. This review examines the key aspects of water management in PEMFCs, including their impact on cell performance, the underlying causes of related issues, and the mechanisms of water transport within these cells. Additionally, it discusses the methods and materials used to enhance water management, highlighting recent advancements and potential directions for future research. Topics such as water transport, water flooding, and water control strategies in PEMFCs are also addressed. Both excess water (flooding) and water depletion (dehydration) can negatively influence fuel cell performance and lifespan. Particular attention is given to water dehydration, with a detailed discussion of its effects on the cathode, Anode, gas diffusion layer, catalyst layer, and flow channels.

Electrochem doi: 10.3390/electrochem6040037

Authors: Ivelina Tsacheva Mehmet Suha Yazici Abdul Hanif Mahadi Aytekin Uzunoglu Dzhamal Uzun

Electrolysis utilizing renewable electricity is an environmentally friendly, non-polluting, and sustainable method of hydrogen production. Seawater is the most desirable and inexpensive electrolyte for this process to achieve commercial acceptance compared to competing hydrogen production technologies. We reviewed metal–organic frameworks as possible electrocatalysts for hydrogen production by seawater electrolysis. Metal–organic frameworks are interesting for seawater electrolysis due to their large surface area, tunable permeability, and ease of functional processing, which makes them extremely suitable for obtaining modifiable electrode structures. Here we discussed the development of metal–organic framework-based electrocatalysts as multifunctional materials with applications for alkaline, PEM, and direct seawater electrolysis for hydrogen production. Their advantages and disadvantages were examined in search of a pathway to a successful and sustainable technology for developing electrode materials to produce hydrogen from seawater.

Electrochem doi: 10.3390/electrochem6040036

Authors: Chloé Laporte Vincent Ball

Melanins are multifunctional biopolymers with unique properties, ranging from UV and radiation protection to antioxidant activity and metal chelation, making them highly attractive for biomedical applications. Despite extensive research, the mechanisms underlying melanin formation remain only partially understood, and access to these biopolymers therefore relies on suitable molecular precursors. While most studies have focused on catecholamine-derived eumelanins such as 3,4-dihydroxyphenylalanine (L-DOPA) and dihydroxyindole (DHI), nitrogen-free precursors such as 1,8-dihydroxynaphthalene (1,8-DHN) are emerging as promising routes to allomelanins. To date, however, these two precursor classes have largely been investigated separately, limiting a broader understanding of structure–function relationships. This review aims to compare electrochemical and redox-based pathways to catecholamine- and DHN-derived materials, emphasizing both their common principles and distinctive features. By bridging these parallel research streams, we propose a methodological framework for guiding future research on melanin-inspired materials and bioelectrochemical technologies.

Electrochem doi: 10.3390/electrochem6040035

Authors: Francisco Augusto Nuñez Perez

Background: Electrochemical impedance spectroscopy (EIS) is indispensable for disentangling charge-transfer, capacitive, and diffusive phenomena, yet reproducible parameter estimation and objective model selection remain unsettled. Methods: We derive closed-form impedances and analytical Jacobians for seven equivalent-circuit models (Randles, constant-phase element (CPE), and Warburg impedance (ZW) variants), enforce physical bounds, and fit synthetic spectra with 2.5% and 5.0% Gaussian noise using hybrid optimization (Differential Evolution (DE) → Levenberg–Marquardt (LM)). Uncertainty is quantified via non-parametric bootstrap; parsimony is assessed with root-mean-square error (RMSE), Akaike Information Criterion (AIC), and Bayesian Information Criterion (BIC); physical consistency is checked by Kramers–Kronig (KK) diagnostics. Results: Solution resistance (Rs) and charge-transfer resistance (Rct) are consistently identifiable across noise levels. CPE parameters (Q,n) and diffusion amplitude (σ) exhibit expected collinearity unless the frequency window excites both processes. Randles suffices for ideal interfaces; Randles+CPE lowers AIC when non-ideality and/or higher noise dominate; adding Warburg reproduces the 45∘ tail and improves likelihood when diffusion is present. The (Rct+ZW)‖CPE architecture offers the best trade-off when heterogeneity and diffusion coexist. Conclusions: The framework unifies analytical derivations, hybrid optimization, and rigorous statistics to deliver traceable, reproducible EIS analysis and clear applicability domains, reducing subjective model choice. All code, data, and settings are released to enable exact reproduction.

Electrochem doi: 10.3390/electrochem6030034

Authors: Ivonne E. Monje Nedher Sanchez-Ramírez Laurence Savignac Pedro H. Camargo Steen B. Schougaard Daniel Bélanger Roberto M. Torresi

Enhancing the safety of lithium-ion batteries (LIBs) by replacing flammable electrolytes is a key challenge. Ionic liquid (IL)-based electrolytes are considered an interesting alternative due to their thermal and chemical stability, high voltage stability window, and tunable properties. This study investigates the electrochemical behavior of two newly synthesized ILs, comparing them to conventional alkyl carbonate-based electrolytes. Nitrogen-doped carbon silicon oxycarbide (NC-SiOC), used as the active material in negative electrodes, was combined with two polymeric binders: poly(acrylic acid) (PAA) and poly(acrylonitrile) (PAN). NC-SiOC/PAN electrodes exhibited a significantly higher initial charge capacity—approximately 25–30% greater than their PAA-based counterparts in the first cycle at 0.1 A g−1 (850–990 mAh g−1 vs. 600–700 mAh g−1), and demonstrated an improved initial Coulombic efficiency (67% vs. 62%). Long-term cycling stability over 1000 cycles at 1.6 A g−1 retained 75–80% of the initial 0.1 A g−1 capacity. This outstanding performance is attributed to the synergistic effects of nitrogen-rich carbonaceous phases within the NC-SiOC material and the cyclized-PAN binder, which facilitate structural stability by accommodating volumetric changes and enhancing solid electrolyte interphase (SEI) stability. Notably, despite the lower ionic transport properties of the IL electrolytes, their incorporation did not compromise performance, supporting their feasibility as safer electrolyte alternatives. These findings offer one of the most promising electrochemical performances reported for SiOC materials to date.

Electrochem doi: 10.3390/electrochem6030033

Authors: Arief S. Budiman Rayya Fajarna Muhammad Asrol Fitya Syarifa Mozar Christian Harito Bens Pardamean Derrick Speaks Endang Djuana

Energy storage systems are becoming increasingly important as more renewable energy systems are integrated into the electrical (or power utility) grid. Low-cost and reliable energy storage is paramount if renewable energy systems are to be increasingly integrated into the power grid. Lead-acid batteries are widely used as energy storage for stationary renewable energy systems and agriculture due to their low cost, especially compared to lithium-ion batteries (LIB). However, lead-acid battery technology suffers from system degradation and a relatively short lifetime, largely due to its charging/discharging cycles. In the present study, we use Machine Learning methodology to estimate the battery degradation in an energy storage system. It uses two types of datasets: discharge condition and lead acid battery data. In the initial analysis, the Support Vector Regression (SVR) method with the RBF kernel showed poor results, with a low accuracy value of 0.0127 and RMSE 5377. On the other hand, the Long Short-Term Memory (LSTM) method demonstrated better estimation results with an RMSE value of 0.0688, which is relatively close to 0.

Electrochem doi: 10.3390/electrochem6030032

Authors: Koichi Jeremiah Aoki Jingyuan Chen

Reported rate constants of charge transfer reactions (CTs) have ranged widely, depending on techniques and timescales. This fact can be attributed to the time-dependent double-layer capacitance (DLC), caused by solvent interactions such as hydrogen bonds. The time variation of the DLC necessarily affects the heterogeneous electrode kinetics. The delay by the solvation, being frequency dispersion, is incorporated into the CT kinetics in this report on the basis of the conventional reaction rate equations. It is different from the absolute rate theory. This report insists on a half value of the transfer coefficient owing to the segregation of the electrostatic energy from the chemical one. The rate equation here is akin to the Butler–Volmer one, except for the power law of the time caused by the delay of the DLC. The dipoles orient successively other dipoles in a group associated with the delay, which resembles that in the DLC. The delay suppresses the observed currents in the form of a negative capacitance. The above behavior was examined with a ferrocenyl derivative by ac impedance methods. The delay from diffusion control was attributed to the negative capacitance rather than the CT, even if the conventional DLC effect was corrected.

Electrochem doi: 10.3390/electrochem6030031

Authors: Jhon Puerres Pablo Ortiz María T. Cortés

TiO2 composites with polypyrrole have gained attention for various applications; however, some reported results on the suitability of this heterojunction for photoelectrochemical water oxidation do not agree. In this sense, it is relevant to further study this material to clarify the role of polypyrrole in this system. Here, TiO2 nanorods were grown on fluorine-doped tin oxide (FTO) substrates by a hydrothermal route; then, polypyrrole coatings were electrochemically synthetized on TiO2 nanorods using a galvanostatic signal. The heterojunctions were characterized by different spectroscopic, microscopic, and electrochemical techniques. As a result, it was found that the polypyrrole underwent a rapid degradation process and that this process occurred independently of the amount of polymer deposited on the TiO2, the illumination direction (back and front of the photoanode), and the type of light used (UV-Vis and Vis). In addition, from the measurements of the band positions of TiO2 and the HOMO level of polypyrrole, it was shown that the TiO2–polypyrrole heterojunction is not suitable for achieving the transfer of photogenerated holes to the electrolyte. These findings contribute to understanding the properties and interaction of two components of wide interest in materials science.

Electrochem doi: 10.3390/electrochem6030030

Authors: Raminta Šakickaitė Zita Sukackienė Virginija Kepenienė Aldona Balčiūnaitė Raminta Stagniūnaitė Gitana Valeckytė Loreta Tamašauskaitė-Tamašiūnaitė

In this study, ternary NiFeP coatings were fabricated on a copper substrate using a simple, fast, and cost-effective electroless deposition method. The coatings were named Ni85Fe4P12, Ni80Fe8P12, and Ni75Fe12P12, indicating 4, 8, and 12 at % of Fe, respectively. The surface morphology and composition of the coatings were characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The activity of the prepared coatings was evaluated using the water-splitting reaction to determine the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in a 1 M KOH electrolyte solution. Electrochemical measurements were carried out in a temperature range from 25 °C to 55 °C. The HER and OER current density values increased by up to 2.58 and 2.13 times, respectively, with temperature increase compared to the result at 25 °C. All three coatings demonstrated activity in both reactions. Ni85Fe4P12 exhibited the highest catalytic efficiency in the HER, with the overpotential of 340 mV at 10 mAcm−2 and a Tafel slope of 61 mVdec−1. In the OER, the efficiency of the NiFeP catalysts correlated with their Fe content. The overpotential was 412 mV for Ni80Fe8P12 and 432 mV for Ni75Fe12P12 at 10 mAcm−2 with Tafel slopes of 96 and 91 mVdec−1, respectively. This study underscores the critical influence of Fe content on the catalytic efficiency of NiFeP coatings, with reduced Fe content enhancing HER and increased Fe content benefits OER.

Electrochem doi: 10.3390/electrochem6030029

Authors: Md Mozammal Raju Yi Ding Qifeng Zhang

The development of high-performance solid electrolytes is critical to advancing solid-state lithium-ion batteries (SSBs), with lithium lanthanum zirconium oxide (LLZO) emerging as a leading candidate due to its chemical stability and wide electrochemical window. In this study, we systematically investigated the effects of cation dopants, including aluminum (Al3+), tantalum (Ta5+), gallium (Ga3+), and rubidium (Rb+), on the structural, electronic, and ionic transport properties of LLZO using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. It appeared that, among all simulated results, Al-LLZO exhibits the highest ionic conductivity of 1.439 × 10−2 S/cm with reduced activation energy of 0.138 eV, driven by enhanced lithium vacancy concentrations and preserved cubic-phase stability. Ta-LLZO follows, with a conductivity of 7.12 × 10−3 S/cm, while Ga-LLZO and Rb-LLZO provide moderate conductivity of 3.73 × 10−3 S/cm and 3.32 × 10−3 S/cm, respectively. Charge density analysis reveals that Al and Ta dopants facilitate smoother lithium-ion migration by minimizing electrostatic barriers. Furthermore, Al-LLZO demonstrates low electronic conductivity (1.72 × 10−8 S/cm) and favorable binding energy, mitigating dendrite formation risks. Comparative evaluations of radial distribution functions (RDFs) and XRD patterns confirm the structural integrity of doped systems. Overall, Al emerges as the most effective and economically viable dopant, optimizing LLZO for scalable, durable, and high-conductivity solid-state batteries.

Electrochem doi: 10.3390/electrochem6030028

Authors: Ping Li Ziyu Cui Mengshuang Wang Junxian Yang Mingli Hu Qiqing Cheng Shi Wang

Metal–organic frameworks (MOFs) have characteristics such as a large specific surface area, distinct functional sites, and an adjustable pore size. However, the inherent low conductivity of MOFs significantly affects the charge transfer efficiency when they are used for electrocatalytic sensing. Combining MOFs with conductive materials can compensate for these deficiencies. For MOF/metal nanoparticle composites (e.g., composites with gold, silver, platinum, and bimetallic nanoparticles), the high electrical conductivity and catalytic activity of metal nanoparticles are utilized, and MOFs can inhibit the agglomeration of nanoparticles. MOF/carbon-based material composites integrate the high electrical conductivity and large specific surface area of carbon-based materials. MOF/conductive polymer composites offer good flexibility and tunability. MOF/multiple conductive material composites exhibit synergistic effects. Although MOF composites provide an ideal platform for electrocatalytic reactions, current research still suffers from several issues, including a lack of comparative studies, insufficient research on structure–property correlations, limited practical applications, and high synthesis costs. In the future, it is necessary to explore new synthetic pathways and seek; inexpensive alternative raw materials.

Electrochem doi: 10.3390/electrochem6030027

Authors: Ahmed Fathy Ahmed M. Agwa

The energy generated from renewable sources has an intermittent nature since solar irradiation and wind speed vary continuously. Hence, their energy should be stored to be utilized throughout their shortage. There are various forms of energy storage systems while the most widespread technique is the battery storage system since its cost is low compared to other techniques. Therefore, batteries are employed in several applications like power systems, electric vehicles, and smart grids. Due to the merits of the lithium-ion (Li-ion) battery, it is preferred over other kinds of batteries. However, the accuracy of the Li-ion battery model is essential for estimating the state of charge (SOC). Additionally, it is essential for consistent simulation and operation throughout various loading and charging conditions. Consequently, the determination of real battery model parameters is vital. An innovative application of the red-billed blue magpie optimizer (RBMO) for determining the model parameters and the SOC of the Li-ion battery is presented in this article. The Shepherd model parameters are determined using the suggested optimization algorithm. The RBMO-based modeling approach offers excellent execution in determining the parameters of the battery model. The suggested approach is compared to other programmed algorithms, namely dandelion optimizer, spider wasp optimizer, barnacles mating optimizer, and interior search algorithm. Moreover, the suggested RBMO is statistically evaluated using Kruskal–Wallis, ANOVA tables, Friedman rank, and Wilcoxon rank tests. Additionally, the Li-ion battery model estimated via the RBMO is validated under variable loading conditions. The fetched results revealed that the suggested approach achieved the least errors between the measured and estimated voltages compared to other approaches in two studied cases with values of 1.4951 × 10−4 and 2.66176 × 10−4.

Electrochem doi: 10.3390/electrochem6030026

Authors: Shu Pei Ng Weiyi Wu Min Qian Yuelong Preston Zhu Xinying Deng Shuyun Chng Yi Jin Tan Yi Qing Kek Shi Jun Zachary Yong Li Wei Low Wenjin Yan

Electrocoagulation is rapidly gaining prominence in wastewater treatment due to its capabilities and less reliance on additional chemicals. While a lot of research efforts have been focused on the influence of the anode material, power supply, and reactor design, the contribution of the cathode to contaminant removal has been less explored. In this study, we investigated the performance of stainless steel (SS-304) and aluminium (Al-6061) electrodes in both similar and dissimilar configurations for a 120 min electrocoagulation treatment of spent machinery coolant. The anode–cathode configurations, including SS-SS, Al-Al, SS-Al and Al-SS, have been investigated. Additionally, we examined the effects of the initial pH and agitation methods on the process performance. Our findings indicated that the type of cathode could significantly affect the floc formation and contaminant removal. Notably, the combination of an Al anode and SS cathode (Al(A)-SS(C)) demonstrated a synergistic improvement in the Chemical Oxygen Demand (COD), with a removal of 84.3% within a short treatment time (<20 min). The final COD removal of 91.4% was achieved with a turbidity level close to 12 Nephelometric Turbidity Units (NTU). The Al anode readily released the Al ions and formed light flocs at the early stage of electrocoagulation, while the SS cathode generated heavy Fe hydroxides that mitigated the flotation effect. These results demonstrated the cathode’s significant contribution in electrocoagulation, leading to potential savings in the treatment time required.

Electrochem doi: 10.3390/electrochem6030025

Authors: Luke R. Johnson Xiaohua Wang Calita Quesada Xiaojing Wang Rangachary Mukundan Rajesh Ahluwalia

Laboratory data from in-cell tests at and near open circuit potentials (OCV) and ex-situ H2O2 vapor exposure tests are used to develop a fluoride emission rate (FER) model for a state-of-the-art 12-µm thin, low equivalent weight, long-chain perfluorosulfonic acid (PFSA) ionomer membrane that is mechanically reinforced with expanded PTFE and chemically stabilized with 2 mol% cerium as an anti-oxidant. The anode FER at OCV linearly correlates with O2 crossover from the cathode and the high yield of H2O2 at anode potentials, as observed in rotating ring disk electrode (RRDE) studies. The cathode FER may be linked to the energetic formation of reactive hydroxyl radicals (·OH) from the decomposition of H2O2 produced as an intermediate in the two-electron ORR pathway at high cathode potentials. Both anode and cathode FERs are significantly enhanced at low relative humidity and high temperatures. The modeled FER is strongly influenced by the gradients in water activity and cerium concentration that develops in operating fuel cells. Membrane stability maps are constructed to illustrate the relationship between the cell voltage, temperature, and relative humidity for FER thresholds that define H2 crossover failure by chemical degradation over a specified lifetime.

Electrochem doi: 10.3390/electrochem6030024

Authors: Luke Saunders Ronan Baron Benjamin R. Horrocks

An important class of analytes are volatile organic carbons (VOCs), particularly aliphatic primary alcohols. Here, we report the straightforward modification of a commercially available carbon monoxide sensor to detect a range of aliphatic primary alcohols at room temperature. The mass transport mechanisms governing the performance of the sensor were investigated using diffusion in multiple layers of the sensor to model the response to an abrupt change in analyte concentration. The sensor was shown to have a large capacitance because of the nanoparticulate nature of the platinum working electrode. It was also shown that the modified sensor had performance characteristics that were mainly determined by the condensation of the analyte during diffusion through the membrane pores. The sensor was capable of a quantitative amperometric response (sensitivity of approximately 2.2 µA/ppm), with a limit of detection (LoD) of 17 ppm methanol, 2 ppm ethanol, 3 ppm heptan-1-ol, and displayed selectivity towards different VOC functional groups (the sensor gives an amperometric response to primary alcohols within 10 s, but not to esters or carboxylic acids).

Electrochem doi: 10.3390/electrochem6030023

Authors: Gwénaëlle Kéranguéven Ivan Filimonenkov Thierry Dintzer Matthieu Picher

The anodic stability of tungsten carbide (WC) and iron oxide with a spinel structure (Fe3O4) were compared against similar data for nanostructured, boron-doped diamond (BDD), and the benchmark Vulcan XC72 carbon, in view of their eventual application as alternative supports for the anion exchange membrane electrolyzer anode. To this end, metal oxide composites were prepared by the in situ autocombustion (ISAC) method, and the anodic behavior of materials (composites as well as supports alone) was investigated in 1 M NaOH electrolyte by the rotating ring–disc electrode method, which enables the separation oxygen evolution reaction and materials’ degradation currents. Among all supports, BDD has proven to be the most stable, while Vulcan XC72 is the least stable under the anodic polarization, with Fe3O4 and WC demonstrating intermediate behavior. The Co3O4-BDD, -Fe3O4, -WC, and -Vulcan composites prepared by the ISAC method were then tested as catalysts of the oxygen evolution reaction. The Co3O4-BDD and Co3O4-Fe3O4 composites appear to be competitive electrocatalysts for the OER in alkaline medium, showing activity comparable to the literature and higher support stability towards oxidation, either in cyclic voltammetry or chronoamperometry stability tests. On the contrary, WC- and Vulcan-based composites are prone to degradation.

Electrochem doi: 10.3390/electrochem6020022

Authors: Viet-Hung Hoang Duc-Long Nguyen Nguyen Tu Van-Dang Tran Van-Nang Lam Thanh-Tung Duong

Highly dispersion antimony-doped tin oxide (ATO) nanoparticles were synthesized using a (220 °C, 2 L autoclave, medium scale) one-step hydrothermal method with Na2SnO3 and KSb(OH)6 as precursors without a post-sintering process. The particle size reduces to a few nanometers with the increase in Sb content. The resulting various Sb-doping content ATO nanoparticles were coated onto a Ti foil substrate as an electrode for further electrochemical evaluation. The findings demonstrate that the prepared 30% Sb-doped ATO nanoparticles serve as a high-conductivity electrode material with excellent reversibility, substantial specific capacitance, and superior capacitance retention. The 30% ATO electrode exhibits the highest specific capacitance of 343.2 F g−1 at a current density of 1 A g−1 and maintains 93% of its capacitance after the first 10 charge/discharge cycles. The results indicate that ATO materials prepared by the hydrothermal method are promising candidates for supercapacitor electrodes.

Electrochem doi: 10.3390/electrochem6020021

Authors: Abinaya Radhakrishnan Manoja Tharmaraj Anuradha Ramani Nagarajan Srinivasan

In recent years, protecting stainless steel from corrosion has become crucial, particularly in harsh environments. The present study focuses on improving the photocathodic corrosion resistance of 304 stainless steel (304SS) by fabricating TiO2/CuO composite coatings using the spin coating technique with varying CuO weight percentages. Structural characterization through X-ray diffraction (XRD) confirmed the presence of the anatase phase of TiO2 and the successful integration of CuO. Raman spectroscopy demonstrated redshifts in the TiO2 characteristic peaks, suggesting changes in bond lengths attributed to CuO incorporation. These findings were further corroborated by Fourier-transform infrared (FTIR) spectroscopy. Surface characterization showed uniform, porous coatings with pore sizes ranging from 75 to 200 nm, which contributed to improved barrier properties. UV–visible diffuse reflectance spectroscopy (UV-DRS) demonstrated enhanced visible light absorption in the heterostructures. Mott–Schottky analysis confirmed improved charge carrier density and favorable band alignment, facilitating efficient charge separation. The electrochemical performance was evaluated in 3.5% NaCl solution under dark and light environments. The results demonstrated that the TiO2/CuO heterostructure significantly enhanced electron transfer and suppressed electron-hole recombination, providing adequate photocathodic protection. Notably, under illumination, the TiO2/CuO (0.005 g) coating achieved a corrosion potential of −255 mV vs SCE and reduced the corrosion current density to 0.460 × 10−6 mA cm−2. These findings suggest that TiO2/CuO coatings offer a promising, durable, and cost-effective solution for corrosion protection in industries such as oil, shipbuilding, and pipelines.

Electrochem doi: 10.3390/electrochem6020020

Authors: Azhar Abdrakhmanova Alfira Sabitova Binur Mussabayeva Bulbul Bayakhmetova Zhanna Sharipkhan Elmira Yermoldina

Anode-free lithium-ion batteries offer a volumetric energy density approximately 60% higher than that of conventional lithium-ion cells. Despite this advantage, they often experience rapid capacity degradation and a limited cycle life. Optimizing electrolyte formulations—particularly through the use of specific additives, solvents, and lithium salts—is essential to improving these systems. This study explores electrolytes composed of fluorinated and carbonate-based solvents applied in anode-free lithium-ion cells featuring copper as the anode substrate and Li1.05Ni0.33Mn0.33Co0.33O2 as the cathode. In the present work, the ionic conductivity of electrolytes was studied by impedance spectroscopy, and the electrochemical parameters of anode-free lithium-ion cells were compared using these electrolyte solutions: lithium difluoro(oxalato)borat (LIDFOB) salts were used in a mixture of solvents such as fluoroethylene carbonate (FEC) and dimethoxyethane (DME) in a ratio of 3:7 and in a mixture of propylene carbonate (PC) and dimethoxyethane in a ratio of 3:7. Enhanced performance was observed upon the substitution of conventional carbonates with fluorinated co-solvents. The findings suggest that LiDFOB is a thermostable salt, and its high conductivity contributes to the formation and stabilization of the interface of solid electrolytes. The results indicate that at low temperature conditions, a double salt should be used for lithium current sources, for example, 0.4 M LiDFOB and 0.6 M LiBF4, as well as electrolyte additives such as fluoroethylene carbonate and lithium nitrate.

Electrochem doi: 10.3390/electrochem6020019

Authors: Surya Chethana Suresh Gururaj Kudur Jayaprakash Sunitha Mughalihalli Shivashankar Rajendrachari Shashanka Bhavana Rikhari

This study presents the electrochemical detection of caffeic acid using an ester (Diethyl 3,4-dihydroxythiophene-2,5-dicarboxylate)-modified carbon paste electrode (EMCPE). Caffeic acid, a naturally occurring hydroxycinnamic acid with antioxidant properties, was investigated due to its significance in food products and its potential health benefits. The modified electrode demonstrated enhanced sensitivity and selectivity for caffeic acid detection. Voltammetric methods were applied to evaluate the electrode performance. Results indicated that EMCPE has improved electron transfer kinetics and a lower detection limit compared unmodified electrode. Detection and quantification thresholds (LOD and LOQ) were found to be 3.12×10−6 M and 1.04×10−3 M. Density functional theory used to understand the electron transfer properties of Diethyl 3,4-dihydroxythiophene-2,5-dicarboxylate. The study highlights the potential of EMCPE as a reliable and cost-effective sensor to quantify caffeic acid across different sample matrices.

Electrochem doi: 10.3390/electrochem6020018

Authors: Yana Suchikova Serhii Nazarovets Anatoli I. Popov

This study presents a comprehensive bibliometric analysis of scientific publications on electrochemical etching and electrochemical deposition from 1970 to 2023. Using the Science Citation Index Expanded (SCIE) database, we analysed 5166 publications on electrochemical etching and, 30,759 publications on electrochemical deposition. The analysis reveals distinct yet interconnected research landscapes for these two techniques. Electrochemical etching research has focused on themes such as porous silicon, photoluminescence, and applications in photonics, while electrochemical deposition research has centred on energy storage, catalysis, and biosensing applications. Keyword co-occurrence analysis illustrates the progression from fundamental studies to specialised applications in both fields. This study highlights the importance of international collaboration and provides insights into the historical and contemporary advancements in electrochemical methods for nanomaterial synthesis. The findings underscore the complementary nature of electrochemical etching and deposition, driving innovation and offering new opportunities in materials science and technology.

Electrochem doi: 10.3390/electrochem6020017

Authors: Manuel Kasper Manuel Moertelmaier Hartmut Popp Ferry Kienberger Nawfal Al-Zubaidi R-Smith

We demonstrate the reconstruction of battery electrochemical impedance spectroscopy (EIS) curves from time-domain pulse testing and the distribution of relaxation times (DRT) analysis. In the proposed approach, the DRT directly utilizes measured current data instead of simulated current patterns, thereby enhancing robustness against current variations and data anomalies. The method is demonstrated with a simulation, a single cylindrical battery cell experiment, and an experimental EIS of a completely assembled module of 448 cells. For the 3.7 kWh battery module, we applied a transient current pulse and analyzed the dynamic voltage responses. The EIS curves were reconstructed with DRT and compared to experiments across different states of charge (SoC). The experimental EIS data were corrected by a multistep calibration workflow in a frequency range from 50 mHz to 1 kHz, achieving error corrections of up to 80% at 1 kHz. The reconstructed impedances from the pulse test data are in good agreement with the EIS experiments in a broad frequency range, delivering relevant electrochemical information including the ohmic resistance and dynamic time constants of a battery module and its corresponding submodules. With the proposed workflow, rapid pulse tests can be used for extracting electrochemical information faster than standard EIS, with a 67% reduction in measurement time. This time-domain pulsing approach provides an alternative to EIS characterization, making it particularly valuable for battery monitoring, the classification of battery packs upon their return to the manufacturer, second-life applications, and recycling.

Electrochem doi: 10.3390/electrochem6020016

Authors: Yu Duan Yedi Li Tingjun Wu Wei Xu Lei Zhu Qiang Liu Yiying Wang Wenjie Yu

Cobalt electrochemical deposition, with its bottom–up growth properties, is a core technology for creating metal interconnects. Additives are crucial during electrodeposition to control the quality of deposits by adsorbing onto the Co surface. The functional groups of additive molecules are the key to tailoring the adsorption behavior. This study focuses on heteroaromatic thiol additives, including 2-mercaptobenzimidazole (MBI), 2-mercapto-5-benzimidazolesulfonic acid sodium salt dehydrate (MBIS), and 2-mercaptobenzoxazole (MBO). Cyclic voltammetry, chronopotentiometry, quantum chemical calculations, and characterization tests were employed to investigate the adsorption behavior of additive molecules with different functional groups on cobalt. The results indicate that the inhibitory strength of the three additives on electrodeposition follows the following order: MBI > MBIS > MBO. The strong inhibitory effect of MBI primarily stems from the adsorption of the thiol group, the pyridine-like nitrogen in the heterocycle, and the benzene ring. MBIS exhibits reduced inhibitory capability due to the combined effects of the sulfonic acid group and hydrolysis ionization. MBO, with the introduction of an oxygen atom in the heterocycle, shows the weakest adsorption and inhibitory capability among the three.

Electrochem doi: 10.3390/electrochem6020015

Authors: Kassapa U. Gamagedara Dipankar Roy

The manufacturing of integrated circuits involves multiple steps of chemical mechanical planarization (CMP) involving different materials. Mitigating CMP-induced defects is a main requirement of all CMP schemes. In this context, controlling galvanic corrosion is a particularly challenging task for planarizing device structures involving contact regions of different metals with dissimilar levels of corrosivity. Since galvanic corrosion occurs in the reactive environment of CMP slurries, an essential aspect of slurry engineering for metal CMP is to control the surface chemistries responsible for these bimetallic effects. Using a CMP system based on copper and cobalt (used in interconnects for wiring and blocking copper diffusion, respectively), the present work explores certain theoretical and experimental aspects of evaluating and controlling galvanic corrosion in barrier CMP. The limitations of conventional electrochemical tests for studying CMP-related galvanic corrosion are examined, and a tribo-electrochemical method for investigating these systems is demonstrated. Alkaline CMP slurries based on sodium percarbonate are used to planarize both Co and Cu samples. Galvanic corrosion of Co is controlled by using the metal-selective complex forming functions of malonic acid at the Co and Cu sample surfaces. A commonly used corrosion inhibitor, benzotriazole, is employed to further reduce the galvanic effects.

Electrochem doi: 10.3390/electrochem6020014

Authors: Xiujuan Feng Falong Qiu

In the past ten years, many coal mines have encountered the problem of a premature failure of anchor rod materials. Through field investigation and laboratory research, it was found that the premature failure of these bolt materials is mostly caused by mine water corrosion. In this paper, a Zn-Y2O3-Al2O3 composite coating was prepared by an electrodeposition method for the corrosion protection of underground anchors. Through the single-factor experiment method, the co-deposition process of Zn2+ nano-Y2O3 and nano-Al2O3 particles was studied. Microhardness was used as the index to determine the optimum preparation process for the composite coatings. Combined with FSEM and XRD tests, the results showed that the synergistic effect of nano-Y2O3 and nano-Al2O3 particles made the coating grain refined and reduced the coating defects. The hardness of the coating increased from 98.7 Hv to 347.9 Hv, and the hardness and wear resistance of the coating were improved. The hydrophobicity of the Zn-Y2O3-Al2O3 composite coating was improved, and its static contact angle was 93.28°. The corrosion resistance of the composite coating was studied through electrochemical impedance spectroscopy, the Tafel curve, corrosion morphology, and weight loss. Under the synergistic effect of nano-Y2O3 and nano-Al2O3 particles, the self-corrosion current density decreased from 4.21 × 10−4 A/cm2 to 1.06 × 10−5 A/cm2, which confirmed that the Zn-Y2O3-Al2O3 composite coating had better corrosion resistance and durability. After soaking in mine water for 63 days, the Zn-Y2O3-Al2O3 composite coating had no obvious shedding on the surface and was well preserved. The practical application results show that it has excellent corrosion resistance and durability. The Zn-Y2O3-Al2O3 nano-composite coating material has significant potential advantages in the field of corrosion resistance of underground anchor rods.

Electrochem doi: 10.3390/electrochem6020013

Authors: Thomas Burns Liliana DeLatte Gabriela Roman-Martinez Kyra Glassey Paul Ziehl Monirosadat Sadati Ralph E. White Paul T. Coman

Structural batteries, also known as “massless batteries”, integrate energy storage directly into load-bearing materials, offering a transformative alternative to traditional Li-ion batteries. Unlike conventional systems that serve only as energy storage devices, structural batteries replace passive structural components, reducing overall weight while providing mechanical reinforcement. However, achieving uniform and efficient coatings of active materials on carbon fibers remains a major challenge, limiting their scalability and electrochemical performance. This study investigates ultrasonic spray coating as a precise and scalable technique for fabricating composite cathodes in structural batteries. Using a computer-controlled ultrasonic nozzle, this method ensures uniform deposition with minimal material waste while maintaining the mechanical integrity of carbon fibers. Compared to traditional techniques such as electrophoretic deposition, vacuum bag hot plate processing, and dip-coating, ultrasonic spray coating achieved superior coating consistency and reproducibility. Electrochemical testing revealed a specific capacity of 100 mAh/gLFP with 80% retention for more than 350 cycles at 0.5 C, demonstrating its potential as a viable coating solution. While structural batteries are not yet commercially viable, these findings represent a step toward their practical implementation. Further research and optimization will be essential in advancing this technology for next-generation aerospace and transportation applications.

Electrochem doi: 10.3390/electrochem6020012

Authors: Bhavi Pandya Latesh Chaudhari Naresh R. Vaghela

The aim of this study was to enhance and maintain bioelectricity generation from distillery spent wash using a microbial fuel cell (MFC). Electrode materials play a critical role in the generation of bioelectricity in MFCs. Utilizing double oxidant-treated carbon felts in MFC applications increased current density to 749.56 mA/m2 and increased peak power density to 125.23 mW/m2. Electrochemical impedance spectroscopy (EIS) analysis further verified the improved electrocatalytic activity observed in the oxidized carbon felt, consistent with the findings from cyclic voltammetry (CV) and polarization curves, thereby confirming the enhanced performance of the oxidized carbon felt electrode. Overall, the study highlights the significance of electrode morphology and surface modifications in influencing microbial adhesion, electron transport, and the overall efficiency of fuel cells using distillery spent wash as a substrate.

Electrochem doi: 10.3390/electrochem6020011

Authors: Divya Catherin Sesu Ganesan Narendran Saraswathi Ramakrishnan Kumaran Vediappan Sankaran Esakki Muthu Sengottaiyan Shanmugan Karthik Kannan

This review reveals the parameters of next-generation fuel cells for portable applications such as cellular phones, laptops, automobiles, etc. Disputes over issues such as design, fluid dynamics, channel dimensions, thermal management, and water management must be overcome for practical applications. We examine techniques such as microfabrication, material selection for membranes and electrodes, and integration challenges in small-scale devices, in addition to issues like methanol crossover, low efficiency at high methanol concentrations, thermal management, and the cost of materials. The advancements in micro-DMFC stacks and prototype developments are presented, and the challenges relating to micro-DMFCs are also identified and reviewed in detail. The challenges in the development of micro-DMFC applications are also presented, including the need for a better understanding of the anode and cathode catalyst structure and for high catalyst loadings in oxidation-and-reduction reactions. Also, a comprehensive and highly valuable database for advancing innovations and enhancing the understanding of micro-DMFCs for potential applications is provided.

Electrochem doi: 10.3390/electrochem6020010

Authors: R. Aguilar-Sánchez D. A. Durán-Tlachino S. L. Cabrera-Hilerio J. L. Gárate-Morales

The preparation and properties of Nafion–TMS (Nafion–trimethylsilyl) and Nafion–TMS–Ru2+-complex modified GC electrodes are reported for the electrochemical oxidation reaction of adrenaline (AD). The structure of Nafion–TMS was studied by atomic force microscopy. The incorporation of [Ru(bpy)3]2+ and [Ru(phen)3]2+ complexes into Nafion–TMS was investigated by UV-vis spectroscopy, providing information about the interaction of the modified Nafion–TMS–Ru2+-complex composite. According to electrochemical studies, the electrodes modified with this composite polymer showed a faster electron transfer and greatly improved kinetics for the redox reaction of AD in standard solutions when compared to bare and Nafion–TMS modified electrodes. The oxidation current increased linearly with adrenaline concentration in the range from 1 to 20 mM and 1 to 100 mM for Nafion–TMS and the modified Nafion–TMS–Ru2+ complex, respectively. A strong pH dependence on the electroanalytical parameters was found for adrenaline detection, indicating that electron transfer reaction occurs in tandem with proton transfer.

Electrochem doi: 10.3390/electrochem6010009

Authors: Epiphane Zingbe Damgou Mani Kongnine Bienvenu M. Agbomahena Pali Kpelou Essowè Mouzou

In a plant microbial fuel cell (P-MFC), the plant provides the fuel in the form of exudates secreted by the roots, which are oxidised by electroactive bacteria. The immature plant is hampered by low energy yields. Several factors may explain this situation, including the low open-circuit voltage of the plant cell. This is a function of the development of the biofilm formed by the electroactive bacteria on the surface of the anode, in relation to the availability of the exudates produced by the roots. In order to exploit the fertilising role of biochars, a plant cell was developed from C. citratus and grown in a medium to which 5% by mass of coconut shell biochar had been added. Its effect was studied as well as the distance between the electrodes. The potential of Cymbopogon citratus was also evaluated. Three samples without biochar, with inter-electrode distances of 2, 5 and 7 cm, respectively, identified as SCS2, SCS5 and SCS7, and three with the addition of 5 % biochar, with the same inter-electrode distance values, identified as S2, S5 and S7, were prepared. Open-circuit voltage (OCV) measurements were taken at 6 a.m., 1 p.m. and 8 p.m. The results showed that all the samples had high open-circuit voltage values at 1 p.m. Samples containing 5% biochar had open-circuit voltages increased by 16 %, 8.94% and 5.78%, respectively, for inter-electrode distances of 2, 5 and 7 cm compared with those containing no biochar. Furthermore, the highest open-circuit voltage values were obtained for all samples with C. citratus at an inter-electrode distance of 5 cm. The maximum power output of the PMFC with C. citratus in this study was 75.8 mW/m2, which is much higher than the power output of PMFCs in recent studies.

Electrochem doi: 10.3390/electrochem6010008

Authors: Hiroto Tominaga Junichi Tokomoto Kenjiro Onimura Kazuhiro Yamabuki

In this study, we developed lithium–sulfur rechargeable batteries using chemically modified thermoplastic sulfur polymers as cathode active materials, aiming to effectively utilize surplus sulfur resources. The resulting high-sulfur-content resins exhibited self-healing properties, extensibility, and adhesiveness. By leveraging its high solubility in specific organic solvents, we successfully introduced sulfur-based compounds into porous carbon via vacuum impregnation using a solution, rather than conventional thermal impregnation. Charge–discharge measurements of lithium–sulfur (Li-S) secondary batteries assembled with this more uniform composite cathode, compared to those using elemental sulfur, demonstrated an increased discharge capacity in the initial cycles and at higher rates.

Electrochem doi: 10.3390/electrochem6010007

Authors: Claudia Santiago-Ramírez Martha Hernández-Pichardo Arturo Manzo-Robledo Daniel Acuña-Leal Miguel Gracia-Pinilla

The electrocatalytic reduction of nitric oxide and nitrogen dioxide (NOx) remains a significant challenge due to the need for stable, efficient, and cost-effective materials. This study presents a novel support system for NOx reduction in alkaline media, composed of ZrO2-WO3-C (ZWC), synthesized via coprecipitation. Platinum nanoparticles (10 wt.%) were loaded onto ZWC and Vulcan carbon support, using similar methods for comparison. Comprehensive physicochemical and electrochemical analyses (N2 physisorption, XRD, XPS, SEM, TEM, and cyclic and linear voltammetry) revealed that PtZWC outperformed PtC and commercial PtEtek in NOx electrocatalysis. Notably, PtZWC exhibited the highest total electric charge for NOx reduction. At the same time, the hydrogen evolution reaction (HER) was shifted to more negative cathodic potentials, indicating reduced hydrogen coverage and a modified dissociative Tafel mechanism on platinum. Additionally, the combination of WO3 and ZrO2 in ZWC enhanced electron transfer and suppressed HER by reducing NO and hydrogen atom adsorption competition. While the incorporation of WO3 and ZrO2 lowered the surface area to 96 m2/g, it significantly improved pore properties, facilitating better Pt nanoparticle dispersion (3.06 ± 0.85 nm, as confirmed by SEM and TEM). XRD analysis identified graphite and Pt phases, with monoclinic WO3 broadening PtZWC peaks (20–25°). At the same time, XPS confirmed oxidation states of Pt, W, and Zr and tungsten-related oxygen vacancies, ensuring chemical stability and enhanced catalytic activity.

Electrochem doi: 10.3390/electrochem6010006

Authors: Kanya Koothanatham Senthilkumar Rajagopalan Thiruvengadathan Ramanujam Brahmadesam Thoopul Srinivasa Raghava

Sodium-ion batteries (SIBs) have garnered significant attention as a cost-effective and sustainable alternative to lithium-ion batteries (LIBs) due to the abundance and eco-friendly extraction of sodium. Despite the larger ionic radius and heavier mass of sodium ions, SIBs are ideal for large-scale applications, such as grid energy storage and electric vehicles, where cost and resource availability outweigh the constraints of size and weight. A critical component in SIBs is the electrolyte, which governs specific capacity, energy density, and battery lifespan by enabling ion transport between electrodes. Among various electrolytes, composite polymer electrolytes (CPEs) stand out for their non-leakage and non-flammable nature and tunable physicochemical properties. The incorporation of NASICON (Na Super Ionic CONductor) fillers into polymer matrices has shown transformative potential in enhancing SIB performance. NASICON fillers improve ionic conductivity by forming continuous ion conduction pathways and reduce polymer matrix crystallinity, thereby facilitating higher sodium-ion mobility. Additionally, these fillers enhance the mechanical properties and electrochemical performance of CPEs. Hence, this review focuses on the pivotal roles of NASICON fillers in optimizing the properties of CPEs, including ionic conductivity, structural integrity, and electrochemical stability. The mechanisms underlying sodium-ion transport facilitated by NASICON fillers in CPE will be explored, with emphasis on the influence of filler morphology and composition on electrochemical properties. By scrutinizing the recent findings, this review underscores the potential of NASICON-based composite polymer electrolytes as appropriate material for the development of advanced sodium-ion batteries.

Electrochem doi: 10.3390/electrochem6010005

Authors: Melanie Rosen Samir Mahioui Christian Schwab Gerald Dück Martin Finsterbusch

Sodium–ion batteries are emerging as strong competition to lithium–ion batteries in certain market sections. While these cells do not use critical raw materials, they still feature a liquid electrolyte with all its inherent safety issues, like high flammability and toxicity. Alternative concepts like oxide-ceramic-based all-solid-state batteries feature the highest possible safety while still maintaining competitive electrochemical performance. However, production technologies are still in their infancy, especially for Na all-solid-state batteries, and need to be urgently developed to enable solid-state-battery technology using only abundant raw materials. In this study, the additive-free production of freestanding, undoped NaSICON separators via tape-casting is demonstrated, having an extremely high total Na-ion conductivity of up to 2.44 mS·cm−1 at room temperature. Nevertheless, a strong influence of sample thickness on phase purity as well as electrochemical performance is uncovered. Additionally, the effect of self-coating of NaSICON during high-temperature treatment was evaluated as a function of thickness. While advantageous for increasing the stability against Na-metal anodes, detrimental consequences are identified when separator thickness is reduced to industrially relevant values and mitigation measures are postulated.

Electrochem doi: 10.3390/electrochem6010004

Authors: Jaanus Kruusma Enn Lust

The electrochemical properties of the hydrophobic room-temperature ionic liquid 1-propyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide (PMMIm(TFSI)) were investigated, for the first time, using an electrochemical double-layer capacitor-mimicking cell containing two identical-sized micro–mesoporous molybdenum carbide-derived carbon electrodes (MMP-C(Mo2C)), by applying cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Surprisingly, despite the substitution of the slightly acidic hydrogen atom with a methyl group at the carbon atom located between two nitrogen atoms in the imidazolium cation, the EIS and CV measurements demonstrated that PMMIm(TFSI) began to decompose electrochemically at the same cell potential (ΔE) as 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIm(BF4)), specifically at ΔE = 2.75 V. However, the CV and EIS data indicated that PMMIm(TFSI) decomposed with a significantly lower intensity than EMIm(BF4). Therefore, we believe that the use of PMMIm(TFSI) as the electrolyte will enable the construction of safer supercapacitors that can tolerate short periods of over-polarization up to ΔE = 4.0 V. However, when the ΔE ≤ 3.2 V was applied, EMIm(BF4) offered higher maximum power compared to PMMIm(TFSI). We found that the calculated maximum gravimetric power precisely describes the maximum ΔE applicable for a supercapacitor candidate.

Electrochem doi: 10.3390/electrochem6010003

Authors: Dasu Ram Paudel Gopi Chandra Kaphle Bhoj Raj Poudel Mukunda KC Manjinder Singh Gunendra Prasad Ojha

Due to their diverse properties and functionalities, cost-effective transition metal-based nanomaterials have been rigorously studied for electrochemical applications. Ultrathin nanosheets have been identified as the most effective electrodes for catalyzing water-splitting reactions in both acidic and alkaline environments. Here, we reported ZnWO4, a member of the tungstate family, as an effective electrocatalyst for promoting the electrochemical hydrogen evolution reaction. The Zn+2-stabilized tungstate showed a remarkable cathodic reaction during the water-splitting reaction with low overpotential (136 mV at 10 mA cm−2) and small HER kinetics (Tafel Slope = 75.3 mV dec−1) and long-term cyclic durability. The high-valence tungsten stabilized with divalent Zn+2 promotes electron transfer during the reaction, making it an advanced electrocatalyst for green hydrogen production.

Electrochem doi: 10.3390/electrochem6010002

Authors: Chinmaya Kumar Sarangi G. Lilishree Achary Tondepu Subbaiah Raja Kishore Paramguru Sanat Kumar Roy

There is a high demand for nickel hydroxide as an engineering material used in the positive electrode of nickel metal hydride (Ni-MH) rechargeable batteries. These batteries are extensively used in various small instruments, disposable batteries, and electric vehicles. The structure of nickel hydroxide significantly influences the discharge capacity and energy density, key properties of Ni-MH batteries, and this structure is primarily determined by the synthesis method used. In this study, nickel hydroxide was synthesized using an electrochemical precipitation method, with current density acting as a parameter to control the desired phase of the product, whether α-nickel hydroxide, β-nickel hydroxide, or a combination of both. At a current density of 50 A/m2, the synthesized nickel hydroxide demonstrated a smaller particle size and a superior discharge electrochemical property in comparison to that generated at 500 A/m2. The effect of agitation in catholyte was also investigated to examine the change in discharge property of the precipitated material. The product synthesized at 500 A/m2 from an agitated catholyte exhibited a tap density of 1.24 g/cc and an improved discharge capacity of 254 mAh per gram of Ni(OH)2.

Electrochem doi: 10.3390/electrochem6010001

Authors: Zhen Lei Ksenya Mull Nikolay Dimitrov

This research investigates the corrosion behavior of copper (Cu) through a comprehensive analysis of both plain and nanoporous Cu thin films. A combination of weight-loss methods for quantitative analysis, along with polarization testing and scanning electron microscopy, is employed for both quantitative and qualitative assessments of Cu corrosion dynamics. The corrosion mechanisms in chloride and nitrate solutions are compared, with an additional discussion on the influence of atmospheric oxygen (O2). The results demonstrate that chloride ions and the presence of O2 create the most severe corrosion conditions, while the concentration of salts has a relatively minor effect on the corrosion behavior. Notably, the comparative study reveals that nanoporous Cu exhibits a greater corrosion tendency, as indicated by more negative corrosion potentials. However, its corrosion rates are lower than those of plain Cu, as determined by corrosion current density measurements.

Electrochem doi: 10.3390/electrochem5040038

Authors: Verena Šućurović Nives Vladislavić Ivana Škugor Rončević

Cigarette butts are an increasing environmental burden worldwide, and the quantities discarded each year could continue to rise. The chemical composition of cigarette butts, which comprises about 4000 different toxic chemicals, as well as their persistence in the environment and their potential negative effects pose a major threat to the environment as they regularly enter aquatic habitats and endanger water supplies and aquatic species. One effective way to reduce pollution is to recycle cigarette butts. The aim of this study is to evaluate the possibility of using extracts from cigarette butts (filter extract and extract from tobacco residues) as corrosion inhibitors for the Cu10Ni alloy in a 3.5% NaCl solution with a pH of 8 at different temperatures (12 °C, 20 °C and 25 °C). The determination of the electrochemical parameters, i.e., the corrosion behavior of the Cu10Ni alloy in a 3.5% NaCl solution and pH of 8, with and without modification of the alloy surface by cigarette butt extracts was tested using electrochemical measurements (electrochemical impedance spectroscopy and linear and potentiodynamic polarization methods). The surface properties of the Cu10Ni alloy modified with cigarette butt extracts were evaluated by goniometry, SEM analysis and FTIR spectrophotometry. The modification of the surface of the Cu10Ni alloy with an extract of tobacco residue and a filter extract separated from cigarette butts, whose presence on the surface was confirmed by the surface analysis methods, increased the corrosion resistance of the alloy, indicating that these substances have an inhibitory effect. The better inhibition properties (at all temperatures: 12 °C, 20 °C and 25 °C) were exhibited by the filter extract, and the highest inhibition effect was exhibited by the filter extract at 12 °C.

Electrochem doi: 10.3390/electrochem5040037

Authors: Anna F. Claire Peter Zacher Danielle Lehto Daysha Krahn Krysti L. Knoche Gupta

Nafion® is a cation exchange polymer that is commonly used in aqueous energy applications such as fuel cells due to its ability to exclude anions and neutral molecules and increase apparent diffusion of cationic redox molecules. However, this behavior is not well studied in nonaqueous solutions. The behavior of platinum electrodes modified with recast Nafion® films in nonaqueous solutions was observed to be different from its well-studied behavior in aqueous solutions. The reversible redox couple tris(2,2′-bipyridine)ruthenium(II) hexafluorophosphate was studied in the nonaqueous, aprotic solvent acetonitrile with different electrolytes (tetrabutylammonium tetrafluoroborate, tetrabutylammonium trifluoromethanesulfonate, tetrabutylammonium hexafluorophosphate, and ammonium trifluoromethanesulfonate) using cyclic voltammetry and rotating disk voltammetry. An unmodified platinum electrode in the nonaqueous systems and a recast Nafion®-modified platinum electrode equilibrated in an aqueous solution of tris(bipyridine)ruthenium(II)chloride hexahydrate were used as controls. Results indicate that the polymer structure in acetonitrile conditions does not allow apparent (Dahms–Ruff) diffusion but does allow significant physical diffusion that would make Nafion a great immobilization option for modifying electrodes with catalysts in nonaqueous systems.

Electrochem doi: 10.3390/electrochem5040036

Authors: Alhamdu Nuhu Bage Olusola Bamisile Humphrey Adun Paul Takyi-Aninakwa Destina Godwin Ekekeh Qingsong Howard Tu

The innovative design of the microstructure of silicon-based composite anodes in Li-ion batteries holds great potential for overcoming inherent limitations, such as the significant volume change experienced by silicon particles. In this study, TiFeSi2/C composites prepared using micro, nano, and porous silicon showed reversible capacities of 990.45 mAh.g−1, 1137.69 mAh.g−1, and 1045.43 mAh.g−1 at C/10. The results obtained from the electrochemical characterization show that the porous structure of the composite anode material created via acid etching reduced silicon expansion during the lithiation/delithiation processes. The void spaces formed in the inner structure of the porous silicon and the presence of carbon increased the electronic conductivity between the silicon particles and, on the other hand, lowered the overall diffusion distance of Li+. This study confirms that TiFeSi2/C prepared with porous silicon dispersed in a transition metal matrix delivers better electrochemical performance compared to micro and nano silicon with a retention of 80.16%.

Electrochem doi: 10.3390/electrochem5040035

Authors: Alpha Chi Him Tsang Shaobo Ouyang Yang Lv Chi Chung Lee Chi-Wing Tsang Xiao-Ying Lu

Mild conditioned, second-life ternary nickel–cobalt–manganese (NCM) black powder regeneration from spent lithium-ion batteries’ (LIBs) black powder mixture was demonstrated after mild conditioned p-toluenesulphuric acid (PTA)-assisted wet leaching. The NCM ratio was tailored to several combinations (333, 523, 532, and 622) by adding a suitable amount of metal (Ni, Co, Mn)-sulphate salt to the leachate. Regenerated NCM was obtained by co-precipitation with sodium hydroxide pellets and ammonia pH buffering solution, followed by lithium (Li) sintering under ambient air and size sieving. The obtained regenerated NCM powder was used for the energy storage materials (ESM) in coin cell (Li half-cell, CR2032) evaluation. Systematic characterization of regenerated NCM showed that the NCM ratio was close to the target value as assigned in the tailored process, and regenerated 622 (R622) exhibited strong activity in CR2032 coin cell testing among all four ratios with a maximum discharge capacity of 196.6 mAh/g.

Electrochem doi: 10.3390/electrochem5040034

Authors: Rani Melati Sukma Dyah Iswantini Novik Nurhidayat Mohamad Rafi

This work describes the development of an electrochemical biosensor method based on bacterial consortia to determine antioxidant capacity. The bacterial consortium used is a combination of bacteria from the genera Bacillus and Pseudomonas which can produce the enzymes tyrosinase and laccase. The consortium bacteria were immobilized on the surface of the screen-printed carbon electrode (SPCE) to form a biofilm. Biofilms were selected based on the highest current response evaluated electrochemically using cyclic voltammetry analysis techniques. Optimum consortium biofilm conditions were obtained in a phosphate buffer solution of pH 7, and biofilm formation occurred on day 7. This work produces analytical performance with a coefficient of determination (R2) of 0.9924. The limit of detection (LOD) and limit of quantification (LOQ) values are 0.5 µM and 10 µM, respectively. The biosensor showed a stable response until the 10th week. This biosensor was used to measure the antioxidant capacity of five extracts, and the results were confirmed using a standard method, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. The highest antioxidant capacity is guava extract and the lowest is tempuyung extract. Thus, the development of this biosensor method can be used as an alternative for measuring antioxidant capacity.

Electrochem doi: 10.3390/electrochem5040033

Authors: Keqiang Ding Weijia Li Mengjiao Li Ying Bai Xiaoxuan Liang Hui Wang

For the first time, carbon-particle-supported palladium-based cobalt composite electrocatalysts (abbreviated as PdxCoy/CPs) were prepared using a calcination–hydrothermal process–hydrothermal process (denoted as CHH). The catalysts of PdxCoy/CPs prepared using CoC2O4·2H2O, (CH3COO)2Co·4H2O, and metallic cobalt were named catalyst c1, c2, and c3, respectively. For comparison, the catalyst prepared in the absence of a Co source (denoted as Pd/CP) was identified as catalyst c0. All fabricated catalysts were thoroughly characterized by XRD, EDS, XPS, and FTIR, indicating that PdO, metallic Pd, carbon particles, and a very small amount of cobalt oxide were the main components of all produced catalysts. As demonstrated by the traditional electrochemical techniques of CV and CA, the electrocatalytic performances of PdxCoy/CP towards the ethanol oxidation reaction (EOR) were significantly superior to that of Pd/CP. In particular, c1 showed an unexpected electrocatalytic activity for EOR; for instance, in the CV test, the peak f current density of EOR on catalyst c1 was 129.3 mA cm−2, being about 10.7 times larger than that measured on Pd/CP, and in the CA test, the polarized current density of EOR recorded for c1 after 7200 s was still about 2.1 mA cm−2, which was larger than that recorded for Pd/CP (0.6 mA cm−2). In the catalyst preparation process, except for the elements of C, O, Co, and Pd, no other elements were involved, which was thought to be the main contribution of this preliminary work, being very meaningful to the further exploration of Pd-based composite EOR catalysts.

Electrochem doi: 10.3390/electrochem5040032

Authors: Keqiang Ding Weijia Li Mengjiao Li Mengyao Di Ying Bai Xiaoxuan Liang Hui Wang

For the first time, nitrogen- and carbon-present tin dioxide-supported palladium composite catalysts (denoted as Pd/N-C-SnO2) were prepared via an HCH method (HCH is the abbreviation for the hydrothermal process–calcination–hydrothermal process preparation process). In this work, firstly, three catalyst carriers (denoted as cc) were prepared using a hydrothermal-process-aided calcination method, and catalyst carriers prepared using ammonia monohydrate (NH3∙H2O), N,N-dimethylformamide (C3H7NO) and triethanolamine (C6H15NO3) as the nitrogen sources were nominated as cc1, cc2 and cc3, respectively. Secondly, these catalyst carriers were reacted with palladium oxide monohydrate (PdO·H2O) hydrothermally to generate catalysts c1, c2 and c3. As testified by XRD and XPS, besides carbon materials and the N-containing substances, the main substances of all prepared catalysts were SnO2 and metallic palladium (Pd). Above all things, all resultant catalysts, especially c2, showed a prominent electrocatalytic activity towards the ethanol oxidation reaction (EOR). As indicated by the CV (cyclic voltammetry) results, all fabricated catalysts presented a clear electrocatalytic activity towards the EOR. In the CA (chronoamperometry) measurement, the faradaic current density of EOR measured on c2 at −0.27 V vs. an SCE (saturated calomel electrode) after 7200 s was still maintained at about 5.6 mA cm−2. Preparing a novel catalyst carrier, N-C-SnO2, and preparing a new EOR catalyst, Pd/N-C-SnO2, were the principal dedications of this preliminary work, which was very beneficial to the development of Pd-based EOR catalysts.

Electrochem doi: 10.3390/electrochem5040031

Authors: Ung-Il Kang

In this study, vanadium (3.5+) electrolyte was prepared for vanadium redox flow batteries (VRFBs) through a reduction reaction using a batch-type hydrothermal reactor, differing from conventional production methods that utilize VOSO4 and V2O5. The starting material, V2O5, was mixed with various concentrations (0.8 M, 1.2 M, 1.6 M, 2.0 M) of citric acid (CA) as the reducing agent and stirred for 60 min at 90 °C using a hot plate to ensure complete dispersion in the solution. The resulting solution was subsequently subjected to a hydrothermal reduction reaction (HRR) furnace at 150 °C for 24 h to generate vanadium (3.5+). The mixed states of the produced vanadium (3+) and vanadium (4+) were confirmed using UV-vis spectroscopy. The electrochemical properties of the electrolyte were investigated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), revealing that the optimal concentration of the CA was 1.6 M. The current efficiency, energy efficiency, and voltage efficiency of the electrolyte produced via the HRR process was compared with that prepared using VOSO4 in charge and discharge experiments. The results demonstrate that the HRR process yields an enhanced electrolyte across all efficiency metrics produced through the given improved performance in all efficiencies. These findings indicate that the HRR process using citric acid can facilitate the straightforward preparation of vanadium (3.5+) electrolyte, making it suitable for large-scale production.

Electrochem doi: 10.3390/electrochem5040030

Authors: Pooja D. Walimbe Rajeev Kumar Amit Kumar Shringi Obed Keelson Hazel Achieng Ouma Fei Yan

This study investigates the underlying mechanisms of hydrogen peroxide (H₂O₂) sensing using a composite material of bismuth oxide and bismuth oxyselenide (Bi2OxSey). The antagonistic effect of tungsten (W)-doping on the electrochemical behavior was also examined. Undoped, 2 mol%, 4 mol%, and 6 mol% W-doped Bi2OxSey nanostructures were synthesized using a one-pot solution phase method involving selenium powder and hydrazine hydrate. W-doping induced a morphological transformation from nanosheets to spherical nanoparticles and amorphization of the bismuth oxyselenide phase. Electrochemical sensing measurements were conducted using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). H₂O₂ detection was achieved over a wide concentration range of 0.02 to 410 µM. In-depth CV analysis revealed the complex interplay of oxidation-reduction processes within the bismuth oxide and Bi2O2Se components of the composite material. W-doping exhibited an antagonistic effect, significantly reducing sensitivity. Among the studied samples, undoped Bi2OxSeγ demonstrated a high sensitivity of 83 μA μM⁻1 cm⁻2 for the CV oxidation peak at 0 V, while 6 mol% W-Bi2OxSey became completely insensitive to H2O2. Interestingly, DPV analysis showed a reversal of sensitivity trends with 2 and 4 mol% W-doping. The applicability of these samples for real-world analysis, including rainwater and urine, was also demonstrated.

Electrochem doi: 10.3390/electrochem5040029

Authors: Trapa Banik Indranil Bhattacharya Kirankumar Venkatesan Savunthari Sanjeev Mukerjee Webster Adepoju Abiodun Olatunji

Manganese- and iron-rich P2-type Na0.67Fe0.5Mn0.5O2 (NFM) has garnered significant interest as a promising cathode candidate due to the natural abundance of Fe and Mn along with a high redox couple of Fe3+/Fe4+ and Mn3+/Mn4+. Despite all these merits, NFM suffers from structural instability during cycling, arising from the destructive Jahn-Teller (JT) distortion effect of Mn3+/Mn4+ during charging and Fe4+/Fe3+ during discharging. In this research, a novel P2-type transition metal-oxide cathode Na0.67Fe0.5−2xMn0.5TixVxO2 was synthesized by doping a tiny fraction of two electrochemically inactive elements, Titanium (Ti) and Vanadium (V), into Mn-rich Na0.67Fe0.5Mn0.5O2 (NFM) that mitigated the JT effect substantially and ameliorated the stability of the SIB during cycling. These exhaustive structural and morphological comparisons provided insights into the effects of V and Ti doping on stabilizing surface structures, reducing Jahn Teller distortion, enhancing stability and capacity retention, and promoting the Na+ carrier transport mechanism. Moreover, the electrochemical analysis, such as the galvanostatic charge/discharge profile, validates the capacity improvement via Ti and V co-doping into NFM cathode. The initial discharge capacity of the 2% Ti/V-doped Na0.67Fe0.48Mn0.5Ti0.01V0.01O2 (2NFMTV) was found to be 187.12 mAh g−1 at a rate of 0.1 C, which was greater than the discharge capacity of 175.15 mAh g−1 observed for pure NFM (Na0.67Mn0.5Fe0.5O2). In contrast, 2NFMTV exhibited a noteworthy capacity retention of 46.1% when evaluated for its original capacity after undergoing 150 cycles at a rate of 0.1 C. This research also established a structural doping approach as a feasible technique for advancing the progress of next-generation Sodium-ion Batteries.

Electrochem doi: 10.3390/electrochem5040028

Authors: Dewen Kong Haijing Liu Si Chen Meiyuan Wu

The lithium-ion battery (LIB) is the key energy storage device for electric transportation. The thick electrode (single-sided areal capacity >4.0 mAh/cm2) design is a straightforward and effective strategy for improving cell energy density by improving the mass proportion of electroactive materials in whole cell components and for reducing cost of the battery cell without involving new chemistries of uncertainties. Thus, selecting a low-cost and environmentally friendly fabrication process to achieve a thick cathode electrode with good electrochemical performance is of strong interest. This study investigated the impact of fabrication processes on the performance of thick LiNi0.75Mn0.25O2 (NM75) cathode electrodes in pouch cells. Two fabrication methods were compared: the conventional polyvinylidene fluoride (PVDF)-based slurry casting method (C-NM75) and the polytetrafluoroethylene (PTFE)-based powder fibrillating process (F-NM75). The pouch cells with F-NM75 electrodes exhibited significantly improved discharge and charge rate capabilities, with a discharge capacity ratio (3 C vs. C/3) > 62% and a charge capacity ratio (2 C vs. C/3) > 81%. Furthermore, F-NM75 cells demonstrated outstanding C/3 cycling performance, retaining 86% of discharge capacity after 2200 cycles. These results strongly indicated that the PTFE-based powder fibrillating process is a promising solution to construct high-performance thick cathode electrodes for electric vehicles (EVs) applications.

Electrochem doi: 10.3390/electrochem5040027

Authors: Tijana Mutić Vesna Stanković Miloš Ognjanović Vladimir B. Nikolić Guanyue Gao Neso Sojic Dalibor Stanković

The extensive use of the alkaloid quinine (QN) in the cosmetic and food industries has induced major concerns relating to its impact on human health, considering its potential toxicity. Therefore, developing sensitive and selective electrochemical sensors is crucial for monitoring QN in environmental, food, and pharmaceutical samples. To respond to this need, a surfactant-supported green synthesis approach, based on a straightforward, organic solvent-free hydrothermal method was employed to synthesize highly crystalline pseudospherical bismuth oxychloride (BiOCl) nanoparticles. This material was used for the enrichment of carbon paste electrodes and its further utilization for the detection and quantification of quinine. They have superior electrocatalytic performance, due to their size and morphology, and facilitate the interactions of the target with the electrode surface. Under optimal operating conditions, differential pulse voltammetry demonstrated a remarkable feature: a broad linear working range of 10 to 140 μM, a detection limit of 0.14 μM, and a high sensitivity of 1.995 μA μM−1 cm−2. The suggested method’s satisfactory sensitivity, along with its good stability, repeatability, and reproducibility, strongly point to a possible use for identifying quinine in real samples.

Electrochem doi: 10.3390/electrochem5040026

Authors: Aslan Achoh Denis Bondarev Stanislav Melnikov Victor Zabolotsky

New homogeneous bilayer membranes with a thin anion-exchange layer have been developed based on the copolymer of N,N-diallyl-N,N-dimethylammonium chloride (DADMAC) and ethyl methacrylate (EMA) on the surface of a membrane substrate made from polyfluorosulfonic acid (PFSA). The overall and partial current–voltage characteristics, as well as external and internal diffusion-limiting currents, were theoretically and experimentally investigated. Parameters such as specific conductivity, sorption, and diffusion permeability of individual membrane layers were determined, along with effective transport numbers and specific permselectivity of the bilayer homogeneous membranes in mixed solutions of calcium chloride and sodium chloride. It was found that applying a thin anion-exchange layer of DADMAC and EMA to the homogeneous membrane allows for the creation of a charge-selective bilayer membrane with enhanced selectivity toward monovalent metal cations. The specific selectivity of the bilayer membrane for sodium cations increases more than 6-fold (from 0.8 to 4.8). Verification of the obtained experimental data was performed within a four-layer mathematical model with quasi-equilibrium boundary conditions for the diffusion layer (I)/modifying layer (II)/membrane substrate (III)/diffusion layer (IV) in ternary NaCl+CaCl2 solutions.

Electrochem doi: 10.3390/electrochem5030025

Authors: Jing Sun Qiang Guo Wanqing Dai Jian Lin Chen Guozhu Mao Yung-Kang Peng

The development of conductive coatings has significant implications for microelectronics and electrochemistry. However, conductive coatings may exhibit different electrochemical properties when prepared on different substrate materials. This research explores the comparative performance of graphene, graphene oxide (GO), and silver nanoparticle (Ag NP) composites as conductive coatings on diverse substrate materials, including polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), and glass. The study employed various preparation methods, such as mixing conductive materials with substrate materials and preparing copolymer composite materials. The conductive coating approach was found to be the most straightforward and convenient, with broader development prospects and fewer restrictive conditions. The results indicate that the distinct surface characteristics of the substrate materials influence the conductive properties of coating materials. Consequently, results show that graphene exhibits the highest conductivity on all three substrates, while GO is more conductive than Ag NPs on PMMA and PDMS but less conductive than Ag NPs on glass. That offers valuable insights into the selection of substrate materials and coating materials for the preparation of conductive materials.

Electrochem doi: 10.3390/electrochem5030024

Authors: Kazuto Sazawa Yeasna Shanjana Kazuharu Sugawara Hideki Kuramitz

An electrochemical bioassay based on rotating droplet electrochemistry by using an electron-transfer mediator was developed for the evaluation of a wide variety of pollutants such as antibiotics, heavy metals, and pesticides in the water environment. Ferricyanide was used as an electron-transfer mediator for obtaining the catalytic response of Escherichia coli. The electrochemical response of E. coli was measured via hydrodynamic chronoamperometry in a microdroplet on a screen-printed carbon electrode (SPCE). The constructed electrode system successfully evaluates the catalytic response of E. coli solution in the presence of ferricyanide. An assay for antibiotic toxicity on E. coli was carried out. The EC50 for ampicillin, sulfamonomethoxine, chlorotetracycline, tetracycline, and oxytetracycline evaluated by the pre-incubation method were 0.26, 0.77, 5.25, 18.5, and 19.0 µM, respectively. The toxicity order was ampicillin > sulfamonomethoxine > chlorotetracycline > tetracycline > oxytetracycline. The proposed method can be used to evaluate the antibiotic toxicities in different real samples, such as pond water, powder, and raw milk. Recoveries were found in the range of 90 and 99%. The developed methods do not require additional incubation time to evaluate toxicity.

Electrochem doi: 10.3390/electrochem5030023

Authors: Mahfouz Saeed Omar I. González Peña

Cu2(ZnSn)(S)4 (copper, zinc, tin, and sulfide (CZTS)) provides possible advantages over CuInGaSe2 for thin-film photovoltaic devices because it has a higher band gap. Preparing CZTS by electrodeposition because of its high productivity and lower processing costs, electroplating is appealing. Recently published studies reported that the electrodeposition process of CZTS still faces significant obstacles, such as the sulfur atomic ratio (about half of the whole alloy), deposits’ adhesion, film quality, and optical properties. This work introduces an improved bath that facilitates the direct electroplating of CZTS from one processing step. The precursors used were significantly more diluted than the typical baths mentioned in the last few years. An extensive analysis of the electrochemical behavior at various rotation speeds is presented at room temperature (~22 °C). The deposited alloy’s composition and adherence to the molybdenum back contact are examined with agitation. The annealing process was carried out in an environment containing sulfur, and the metal was not added at this stage. The ultimate sulfur composition was adjusted to 50.2%, about the desired atomic ratio. The compound’s final composition was investigated using the Energy-Dispersive X-ray Spectroscopy technique. Finally, X-ray diffraction analysis was applied to analyze CZTS crystallography and to measure thickness.

Electrochem doi: 10.3390/electrochem5030022

Authors: Durgasha C. Poudyal Manish Samson Vikram Narayanan Dhamu Sera Mohammed Claudia N. Tanchez Advaita Puri Diya Baby Sriram Muthukumar Shalini Prasad

Direct testing of pesticide contaminants in drinking water is a challenge. Portable and sensitive sensor platforms are desirable to test water contaminants directly at farm and consumer levels. In this study, we have demonstrated the feasibility of an electrochemical sensor for the direct detection of paraquat (PQ) in drinking water samples. An immunoassay-based sensing platform was fabricated using PQ-specific antibody immobilized on the surface of the electrochemically reduced graphene oxide (rGO) modified screen-printed carbon electrode (rGO-SPCE). Using non-faradaic electrochemical impedance spectroscopy (EIS) as a detection tool, the sensor platform demonstrated a dynamic response for PQ concentration in drinking water ranging from 0.05 ng/mL to 72.9 ng/mL (0.19 to 243.8 nM), with a coefficient of determination (r2) of 0.997 and a limit of detection of 0.05 ng/mL (0.19 nM). Percentage recovery within ±20% error was obtained, and the sensor cross-reactivity test showed a selective response against glyphosate antigen. With the flexibility to use single-frequency EIS and low sample volume, the developed sensor demonstrated testing in water samples directly without any sample pre-processing. This low-volume electroanalytical sensor platforms can be translated into portable testing tools for the detection of various water contaminants.

Electrochem doi: 10.3390/electrochem5030021

Authors: Xiao Deng Wipakorn Jevasuwan Naoki Fukata Akihiro Okamoto

Extracellular electron transfer (EET) by sulfate-reducing bacteria (SRB), such as Desulfovibrio ferrophilus IS5, enables bacterial interactions with minerals, which are vital for biogeochemical cycling and environmental chemistry. Here, we explore the direct EET mechanisms through outer-membrane cytochromes (OMCs) using IS5 as a model SRB. We employed nanostructured electrodes arrayed with 0, 50, 200, and 500 nm long nanowires (NWs) coated with indium–tin–doped oxide to examine the impact of electrode morphology on the direct EET efficacy. Compared to flat electrodes, NW electrodes significantly enhanced current production in IS5 with OMCs. However, this enhancement was diminished when OMC expression was reduced. Differential pulse voltammetry revealed that NW electrodes specifically augmented redox peaks associated with OMCs without affecting those related to redox mediators, suggesting that NWs foster direct EET through OMCs. Scanning electron microscopy observations following electrochemical analyses revealed a novel vertical cell attachment and aggregation on NW electrodes, contrasting with the horizontal monolayer cell attachment on flat electrodes. This study presents the first evidence of the critical role of electrode nanoscale topography in modulating SRB cell orientation and aggregation behavior. The findings underscore the significant influence of electrode morphology on the direct EET kinetics, highlighting the potential impact of mineral morphology on mineral reduction and biogeochemical processes.

Electrochem doi: 10.3390/electrochem5030020

Authors: Gururaj Kudur Jayaprakash Kaustubha Mohanty

The escalating concern over environmental pollutants, particularly brominated flame retardants (BFRs), demands sophisticated detection methodologies for compounds like Tetrabromobisphenol A (TBBPA) and Hexabromocyclododecane (HBCD). Amidst these challenges, advancements in electrochemical detection have notably focused on the integration of inorganic modifiers within carbon electrodes. Inorganic nanoparticles, known for their catalytic and surface-enhancing properties, play a pivotal role in augmenting the sensitivity and selectivity of electrode-based detection systems. These modifiers, encompassing materials such as graphene, CeO2 nanocubes, and metal-organic frameworks, among others, have revolutionized the capabilities of carbon-based electrodes in accurately identifying specific BFRs.

Electrochem doi: 10.3390/electrochem5030019

Authors: Susmi Anna Thomas Jayesh Cherusseri Deepthi N. Rajendran

Battery-type hybrid supercapacitors (HSCs) (otherwise known as supercapatteries) are novel electrochemical energy storage devices bridge the gap between rechargeable batteries and traditional SCs. Herein, we report the synthesis of layered two-dimensional (2D) nickel disulfide (NiS2) nanosheets (NSNs) modified with poly(3,4-ethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) and their successful implementation in battery-type SCs. Initially, a layered 2D NSN is synthesized via a microwave-assisted hydrothermal method and further used as a template to coat PEDOT:PSS in order to prepare NiS2@PEDOT:PSS nanocomposite electrodes by a facile drop-casting method. This is the first-time report on the synthesis of a hierarchical NiS2@PEDOT:PSS nanocomposite electrode for battery-type HSC applications. An asymmetric battery-type HSC fabricated with NSN@PEDOT:PSS nanocomposite as positrode and activated carbon as negatrode delivers a maximum energy density of 52.1 Wh/kg at a current density of 1.6 A/g with a corresponding power density of 2500 W/kg.

Electrochem doi: 10.3390/electrochem5030018

Authors: Zeyu Gu Jhen-Yang Wu Yiming Jiang Tomoyuki Kurioka Chun-Yi Chen Hwai-En Lin Xun Luo Daisuke Yamane Masato Sone Tso-Fu Mark Chang

Ni–W alloys have received considerable interest as a promising structural material for microelectromechanical systems (MEMS) due to their exceptional properties, including hardness, ductility, corrosion resistance, and thermal stability. However, the electrodeposition of Ni–W alloys in the MEMS fabrication process to achieve intact structures with a thickness of several tens of micrometers is challenging due to the occurrence of cracking caused by side reactions and internal stresses during the electrodeposition process. To address this issue, our focus was on pulsed reverse electrodeposition (PRE) as a potential solution. The utilization of the PRE technique allows for a high concentration of reactive species on the electrode surface, thereby mitigating side reactions such as hydrogen generation. In this study, we examined the effects of the PRE method on the morphological characteristics, average crystal grain size, Vickers hardness, and micro-mechanical properties of Ni–W alloys.

Electrochem doi: 10.3390/electrochem5030017

Authors: Md Shafiul Islam Alan Branigan Dexian Ye Maryanne M. Collinson

This work describes the fabrication and characterization of a new high surface area nanocomposite electrode containing reduced graphene oxide (rGO) and titanium nitride (TiN) for electrochemical applications. This approach involves electrochemically depositing rGO on a high surface area TiN nanorod array electrode to form a new nanocomposite electrode. The TiN nanorod array was first formed by the glancing angle deposition technique in a DC (Direct Current) sputtering system. GO flakes of ~1.5 μm in diameter, as confirmed by Dynamic Light Scattering (DLS), were electrodeposited on the nanostructured TiN electrode via the application of a fixed potential for one hour. The surface morphology of the as-prepared rGO/TiN electrode was evaluated by scanning electron microscopy (SEM) and the presence of rGO on TiN was confirmed by Raman Microscopy. The CV shows an increase in the capacitive current at rGO/TiN as compared to TiN. The rGO decorated TiN electrode was then used for analyzing the electrocatalytic oxidation of ascorbic acid and dopamine, and the reduction of nitrate by CV and linear sweep voltammetry (LSV), respectively. CV or LSV show that the electrochemical kinetics of these three analytes are significantly faster on rGO/TiN than TiN itself. Overall, the rGO/TiN electrode showed better electrochemical behavior for biomolecules like ascorbic acid and dopamine as well as another target analyte, nitrate ions, compared to TiN by itself.

Electrochem doi: 10.3390/electrochem5020016

Authors: Denis Miroshnichenko Kateryna Shmeltser Maryna Kormer Yevhen Soloviov Serhiy Pyshyev Bohdan Korchak Mariia Shved Yuriy Prysiazhnyi

The influence of the component composition of coal batches and the final temperature of the coking process on the resistivity of coke was studied. Taking into account that the resistivity and reactivity are influenced by some common factors, such as the temperature level and coke readiness, which indicates the orderliness of its structure, the relationship between these indicators was established. The electrical resistivity can be considered a cumulative characteristic of coke properties, as evidenced by the mathematical dependencies of the change electrical resistance on the ash content, sulfur content, volatile yield, and petrographic composition. Analysis of the dependencies and their statistical evaluation indicate that the studied relationships are characterized by high values of correlation (0.6–0.84). The proposed regression equations can be recommended for optimizing the component composition and quality of production batches, given their significant impact on the resistivity of coke. This is especially relevant when coke is used in electrothermal processes, since the productivity and the electrical and thermal efficiency of the furnace depends on the resistivity of the coke in electrochemical processes in which carbon materials are used as anodes and lining elements and in the production of capacitor technology. As the resistivity test requires much less time to perform than the reactivity test, it can be considered as an alternative approach to the reactivity testing currently performed for quality control purposes.

Electrochem doi: 10.3390/electrochem5020015

Authors: Nataliia Ivanova Soha Ahmadi Edmund Chan Léa Fournier Sandro Spagnolo Michael Thompson

Electrochemical biosensors are valued for their sensitivity and selectivity in detecting biological molecules. Having the advantage of generating signals that can be directly or indirectly proportional to the concentration of the target analyte, these biosensors can achieve specificity by utilizing a specific biorecognition surface designed to recognize the target molecule. Electrochemical biosensors have garnered substantial attention, as they can be used to fabricate compact, cost-effective devices, making them promising candidates for point-of-care testing (POCT) devices. This study introduces a label-free electrochemical biosensor employing a gold screen-printed electrode (SPE) to detect lysophosphatidic acid (LPA), a potential early ovarian cancer biomarker. We employed the gelsolin–actin system, previously introduced by our group, in combination with fluorescence spectrometry, as a biorecognition element to detect LPA. By immobilizing a gelsolin–actin complex on an SPE, we were able to quantify changes in current intensity using cyclic voltammetry and differential pulse voltammetry, which was directly proportional to the LPA concentration in the solution. Our results demonstrate the high sensitivity of the developed biosensor for detecting LPA in goat serum, with a limit of detection (LOD) and a limit of quantification (LOQ) of 0.9 µM and 2.76 µM, respectively, highlighting its potential as a promising tool for early-stage diagnosis of ovarian cancer.

Electrochem doi: 10.3390/electrochem5020014

Authors: Debora Maria Conti Claudia Urru Giovanna Bruni Pietro Galinetto Benedetta Albini Vittorio Berbenni Doretta Capsoni

In the present study, LiFePO4/CNF self-standing cathodes for LIBs are synthesized by electrospinning. A lower active material amount (12.3 and 34.5 wt%) is used, compared to the conventional tape-casted cathodes (70–85 wt%). The characterization techniques (XRPD, SEM, TEM, EDS, Raman spectroscopy, and thermogravimetry) confirm that the olivine-type structure of LiFePO4 is maintained in the binder-free electrodes, and the active material is homogeneously dispersed into and within the carbon nanofibers. The electrochemical investigation demonstrates that higher Li+ diffusion coefficients (1.36 × 10−11 cm2/s) and improved reversibility are reached for free-standing electrodes, compared to the LiFePO4 tape-casted cathode (80 wt% of active material) appositely prepared for comparison. The 34.5 wt% LiFePO4 self-standing cathode displays a lower capacity fading, good reversibility and stability, enhanced capacity values at C-rates higher than 5C, and a good lifespan when cycled 1000 cycles at 1C and further cycled up to 20C, compared to the tape-casted counterpart. Notably, the improved electrochemical performances are obtained by only the 34.5 wt% of active material. The results evidence the relevant role of the CNF matrix suitable to host LiFePO4, to promote electrolyte permeation and contact with the active material, and to increase the electronic conductivity.

Electrochem doi: 10.3390/electrochem5020013

Authors: Hikaru Kondo Tomoyuki Kurioka Wan-Ting Chiu Chun-Yi Chen Jhen-Yang Wu Tso-Fu Mark Chang Machiko Yamaguchi Hiromichi Kurosu Masato Sone

This study reports on the use of supercritical CO2 (scCO2) for the metallization of ultrahigh-molecular-weight polyethylene (UHMW-PE) filaments, which are used as functional components in weavable devices. UHMW-PE is well known for its chemical and impact resistance, making it suitable for use in bulletproof clothing and shields. However, its chemical resistance poses a challenge for metallization. By utilizing scCO2 as the solvent in the catalyzation process, a uniform and defect-free layer of Ni-P is successfully deposited on the UHMW-PE filaments. The deposition rate of Ni-P is enhanced at higher temperatures during the scCO2 catalyzation. Importantly, the durability of the Ni-P-metalized UHMW-PE filaments is improved when the scCO2 catalyzation is carried out at 120 °C, as evidenced by minimal changes in electrical resistivity after a rolling test.

Electrochem doi: 10.3390/electrochem5020012

Authors: Antonio Ruiz-Gonzalez

Food quality assessment is becoming a global priority due to population growth and the rise of ionic pollutants derived from anthropogenic sources. However, the current methods used to quantify toxic ions are expensive and their operation is complex. Consequently, there is a need for affordable and accessible methods for the accurate determination of ion concentrations in food. Electrochemical sensors based on potentiometry represent a promising approach in this field, with the potential to overcome limitations of the currently available systems. This review summarizes the current advances in the electrochemical quantification of heavy metals and toxic anions in the food industry using potentiometric sensors. The healthcare impact of common heavy metal contaminants (Cd2+, Hg2+, Pb2+, As3+) and anions (ClO4−, F−, HPO4−, SO42−, NO3−, NO2−) is discussed, alongside current regulations, and gold standard methods for analysis. Sensor performances are compared to current benchmarks in terms of selectivity and the limit of detection. Given the complexity of food samples, the percentage recovery values (%) and the methodologies employed for ion extraction are also described. Finally, a summary of the challenges and future directions of the field is provided. An overview of technologies that can overcome the limitations of current electrochemical sensors is shown, including new extraction methods for ions in food.

Electrochem doi: 10.3390/electrochem5020011

Authors: Etienne Dijoux Cédric Damour Frédéric Alicalapa Alexandre Aubier Michel Benne

The ability of a diagnosis tool to observe an abnormal state of a system remains a major issue for health monitoring. For that purpose, several diagnosis tools have been proposed in the literature. Most of them are developed for specific system characterization, and the genericity of the approaches is not considered. Indeed, most approaches proposed in the literature are based on an expert offline consideration that makes it hard to apply the strategy to other systems. It is therefore important to develop a diagnostic tool that takes as little as possible expert knowledge to reduce the dependency between the tool and the system. This paper, therefore, focuses on the application of a generic diagnosis tool on an open cathode fuel cell. The goal is to feed the diagnosis algorithm with a voltage measurement and let it proceed to a self-clustering of the signal components. Each cluster’s interpretation remains to be established by the expert point of view that is then involved downstream of the diagnosis tool.

Electrochem doi: 10.3390/electrochem5020010

Authors: Mansi Gandhi

Electrochemistry is a hotspot in today’s research arena. Many different domains have been extended for their role towards the Internet of Things, digital health, personalized nutrition, and/or wellness using electrochemistry. These advances have led to a substantial increase in the power and popularity of electroanalysis and its expansion into new phases and environments. The recent COVID-19 pandemic, which turned our lives upside down, has helped us to understand the need for miniaturized electrochemical diagnostic platforms. It also accelerated the role of mobile and wearable, implantable sensors as telehealth systems. The major principle behind these platforms is the role of electrochemical immunoassays, which help in overshadowing the classical gold standard methods (reverse transcriptase polymerase chain reaction) in terms of accuracy, time, manpower, and, most importantly, economics. Many research groups have endeavoured to use electrochemical and bio-electrochemical tools to overcome the limitations of classical assays (in terms of accuracy, accessibility, portability, and response time). This review mainly focuses on the electrochemical technologies used for immunosensing platforms, their fabrication requirements, mechanistic objectives, electrochemical techniques involved, and their subsequent output signal amplifications using a tagged and non-tagged system. The combination of various techniques (optical spectroscopy, Raman scattering, column chromatography, HPLC, and X-ray diffraction) has enabled the construction of high-performance electrodes. Later in the review, these combinations and their utilization will be explained in terms of their mechanistic platform along with chemical bonding and their role in signal output in the later part of article. Furthermore, the market study in terms of real prototypes will be elaborately discussed.

Electrochem doi: 10.3390/electrochem5020009

Authors: Vahide Ghanooni Ahmadabadi Md Mokhlesur Rahman Ying Chen

A silicon nanoparticle–graphite nanosheet composite was prepared via a facile ball milling process for use as the anode for high-rate lithium-ion batteries. The size effect of Si nanoparticles on the structure and on the lithium-ion battery performance of the composite is evaluated. SEM and TEM analyses show a structural alteration of the composites from Si nanoparticle-surrounded graphite nanosheets to Si nanoparticle-embedded graphite nanosheets by decreasing the size of Si nanoparticles from 250 nm to 40 nm. The composites with finer Si nanoparticles provide an effective nanostructure containing encapsulated Si and free space. This structure facilitates the indirect exposure of Si to electrolyte and Si expansion during cycling, which leads to a stable solid–electrolyte interphase and elevated conductivity. An enhanced rate capability was obtained for the 40 nm Si nanoparticle–graphite nanosheet composite, delivering a specific capacity of 276 mAh g−1 at a current density of 1 C after 1000 cycles and a rate capacity of 205 mAh g−1 at 8 C.

Electrochem doi: 10.3390/electrochem5010008

Authors: Anastasia Leonova Natalia Leonova Lyudmila Minchenko Andrey Suzdaltsev

The possibility of using Si-based anodes in lithium-ion batteries is actively investigated due to the increased lithium capacity of silicon. The paper reports the preparation of submicron silicon fibers on glassy carbon in the KI–KF–KCl–K2SiF6 melt at 720 °C. For this purpose, the parameters of silicon electrodeposition in the form of fibers were determined using cyclic voltammetry, and experimental samples of ordered silicon fibers with an average diameter from 0.1 to 0.3 μm were obtained under galvanostatic electrolysis conditions. Using the obtained silicon fibers, anode half-cells of a lithium-ion battery were fabricated, and its electrochemical performance under multiple lithiations and delithiations was studied. By means of voltametric studies, it is observed that charging and discharging the anode based on the obtained silicon fibers occurs at potentials from 0.2 to 0.05 V and from 0.2 to 0.5 V, respectively. A change in discharge capacity from 520 to 200 mAh g−1 during the first 50 charge/discharge cycles at a charge current of 0.1 C and a Coulombic efficiency of 98–100% was shown. The possibility of charging silicon-based anode samples at charging currents up to 2 C was also noted; the discharge capacity ranged from 25 to 250 mAh g−1.

Electrochem doi: 10.3390/electrochem5010007

Authors: Elizaveta Y. Evshchik Sophia S. Borisevich Margarita G. Ilyina Edward M. Khamitov Alexander V. Chernyak Tatiana A. Pugacheva Valery G. Kolmakov Olga V. Bushkova Yuri A. Dobrovolsky

Determining the oxidation potential (OP) of lithium-ion battery (LIB) electrolytes using theoretical methods will significantly speed up and simplify the process of creating a new generation high-voltage battery. The algorithm for calculating OP should be not only accurate but also fast. Our work proposes theoretical principles for evaluating the OP of LIB electrolytes by considering LiDFOB solutions with different salt concentrations in EC/DMC solvent mixtures. The advantage of the new algorithm compared to previous versions of the theoretical determination of the oxidation potential of electrolyte solutions used in lithium-ion batteries for calculations of statistically significant complexes, the structure of which was determined by the molecular dynamics method. This approach significantly reduces the number of atomic–molecular systems whose geometric parameters need to be optimized using quantum chemical methods. Due to this, it is possible to increase the speed of calculations and reduce the power requirements of the computer performing the calculations. The theoretical calculations included a set of approaches based on the methods of classical molecular mechanics and quantum chemistry. To select statistically significant complexes that can make a significant contribution to the stability of the electrochemical system, a thorough analysis of molecular dynamics simulation trajectories was performed. Their geometric parameters (including oxidized forms) were optimized by QM methods. As a result, oxidation potentials were assessed, and their dependence on salt concentration was described. Here, we once again emphasize that it is difficult to obtain, by calculation methods, the absolute OP values that would be equal (or close) to the OP values estimated by experimental methods. Nevertheless, a trend can be identified. The results of theoretical calculations are in full agreement with the experimental ones.

Electrochem doi: 10.3390/electrochem5010006

Authors: Aslan Achoh Denis Bondarev Elena Nosova Stanislav Melnikov

This study focuses on the modification of ion-exchange membranes by incorporating a phosphorylated dendrimer into sulfonated polytetrafluoroethylene membranes to enhance the specific selectivity between mono-/divalent ions, using the Ca2+/Na+ pair as an example. This research employs mechanical, physicochemical, and electrochemical analyses to explore the effects of P-H20 incorporation on membrane properties. Bulk modification significantly increases membrane selectivity towards calcium ions (the specific permselectivity coefficient rises from 1.5 to 7.2), while maintaining the same level of the limiting current density. Other findings indicate that bulk modification significantly changes the transport-channel structure of the membrane and alters the mechanism of over-limiting mass transfer. The over-limiting current for the pristine membrane is mainly due to non-equilibrium electroconvection, while modified membranes actively participate in the water-splitting reaction, leading to the suppression of the electroconvection. Despite this drawback, the decrease of the over-limiting potential drop results in a decrease in specific energy consumption from 0.11 to 0.07 kWh/mol. In the underlimiting current mode, the specific energy consumption for all studied membranes remains within the same limits of 0.02–0.03 kWh/mol.

Electrochem doi: 10.3390/electrochem5010005

Authors: Vivek Kumar Singh Bibhudatta Malik Rajashree Konar Efrat Shawat Avraham Gilbert Daniel Nessim

The electrocatalytic oxygen evolution reaction (OER) is an arduous step in water splitting due to its slow reaction rate and large overpotential. Herein, we synthesized glycerate-anion-intercalated nickel–iron glycerates (NiFeGs) using a one-step solvothermal reaction. We designed various NiFeGs by tuning the molar ratio between Ni and Fe to obtain Ni4Fe1G, Ni3Fe1G, Ni3Fe2G, and Ni1Fe1G, which we tested for their OER performance. We initially analyzed the catalytic performance of powder samples immobilized on glassy carbon electrodes using a binder. Ni3Fe2G outperformed the other NiFeG compositions, including NiFe layered double hydroxide (LDH). It exhibited an overpotential of 320 mV at a current density of 10 mA cm–2 in an electrolytic solution of pH 14. We then synthesized carbon paper (CP)-modified Ni3Fe2G as a self-supported electrode (Ni3Fe2G/CP), and it exhibited a high current density (100 mA cm−2) at a low overpotential of 300 mV. The redox peak analysis for the NiFeGs revealed that the initial step of the OER is the formation of γ-NiOOH, which was further confirmed by a post-Raman analysis. We extensively analyzed the catalyst’s stability and lifetime, the nature of the active sites, and the role of the Fe content to enhance the OER performance. This work may provide the motivation to study metal-alkoxide-based efficient OER electrocatalysts that can be used for alkaline water electrolyzer applications.

Electrochem doi: 10.3390/electrochem5010004

Authors: Zaheer Masood Haji Muhammad Iftikhar Ahmed Tahiri

Understanding electrochemical reactions at the surface of electrodes requires the accurate calculation of key parameters—the transfer coefficient (α), diffusion coefficient (D0), and heterogeneous electron transfer rate constant (k0). The choice of method to calculate these parameters requires careful consideration based on the nature of the electrochemical reaction. In this study, we conducted the cyclic voltammetry of paracetamol to calculate the values of these parameters using different methods and present a comparative analysis. Our results demonstrate that the Ep − Ep/2 equation for α and the modified Randles–Ševčík equation for D0 is particularly effective for the calculations of these two parameters. The Kochi and Gileadi methods are reliable alternatives for the calculation of k0. Nicholson and Shain’s method using the equation k0 = Ψ(πnD0Fν/RT)1/2 gives the overestimated values of k0. However, the value of k0 calculated using the plot of ν−1/2 versus Ψ (from the Nicholson and Shain equation, where ν is scan rate) agrees well with the values calculated from the Kochi and Gilaedi methods. This study not only identifies optimal methodologies for quasi-reversible reactions but also contributes to a deeper understanding of electrochemical reactions involving complex electron transfer and coupled chemical reactions, which can be broadly applicable in various electrochemical studies.

Electrochem doi: 10.3390/electrochem5010003

Authors: Tijana Mutić Dalibor Stanković Dragan Manojlović Djordje Petrić Ferenc Pastor Vyacheslav V. Avdin Miloš Ognjanović Vesna Stanković

In this work, we successfully prepared a modified cobalt oxide (Co3O4) carbon paste electrode to detect Levofloxacin (LEV). By synthesizing Co3O4 nanoparticles through the chemical coprecipitation method, the electrochemical properties of the electrode and LEV were thoroughly investigated using CV, SWV, and EIS, while material properties were scrutinized using ICP-OES, TEM, SEM, and XRD. The results showed that the prepared electrode displayed a better electrocatalytic response than the bare carbon paste electrode. After optimizing SWV, the electrode exhibited a wide linear working range from 1 to 85 μM at pH 5 of BRBS as the supporting electrolyte. The selectivity of the proposed method was satisfactory, with good repeatability and reproducibility, strongly suggesting a potential application for determining LEV in real samples, particularly in pharmaceutical formulations. The practicality of the approach was demonstrated through good recoveries, and the morphology of the materials was found to be closely related to other parameters, indicating that the developed method can provide a cost-effective, rapid, selective, and sensitive means for LEV monitoring. Overall, this project has made significant progress towards developing a reliable method for detecting LEV and has opened up new opportunities for future research in this field.

Electrochem doi: 10.3390/electrochem5010002

Authors: Adam Cherni Kamel Halouani

At present, direct carbon fuel cells constitute an emerging energy technology that electrochemically converts solid carbon to electricity with high efficiency. The recent trend of DCFCs fueled with biochar from biomass carbonization as green fuel has reinforced the environmental benefits of DCFCs as a clean and sustainable technology. However, there remain new challenges related to some complex unknown kinetic parameters, X=(αa,αc,σg,i0,a,i0,c,ilO2,ilCO2,c,ilCO2,a,ilCO), of the electrochemical conversion of biochar in DCFCs and there is a need for intelligent techniques for prediction and optimization, refering to the available experimental data. The differential evolution (DE) algorithm, which ranked as one of the top performers in optimization competitions with competitive accuracy and convergence speed, was used here for providing the optimized values of these parameters by minimizing the root mean squared errors (RMSE). The proposed technique was then applied to DCFCs fueled by activated pure carbon (APC) using CO2 and CO/CO2 electrochemical models with RMSE around 10−2 and 10−3, respectively. Then, the CO/CO2 model was applied to a DCFC fueled with almond shell biochar (ASB), which displayed a slight increase in RMSE (of the order of 10−2) due to the complex porous structure of ASB and the content of additional chemical elements that affect the electrochemistry of the DCFC and are not considered in the model.

Electrochem doi: 10.3390/electrochem5010001

Authors: Ioannis Christakis Elena Sarri Odysseas Tsakiridis Ilias Stavrakas

Nowadays, the study of air quality has become an increasingly prominent field of research, particularly in large urban centers, given its significant impact on human health. In many countries, government departments and research centers use official high-cost scientific instruments to monitor air quality in their regions. Meanwhile, concerned citizens interested in studying the air quality of their local areas often employ low-cost air quality sensors for monitoring purposes. The optimization and evaluation of low-cost sensors have been a field of research by many research groups. This paper presents an extensive study to identify the safe percentage change limits that low-cost electrochemical air quality sensors can have, in order to optimize their measurements. For this work, three low-cost air quality monitoring stations were used, which include an electrochemical sensor for nitrogen dioxide (NO2) (Alphasense NO2-B43F) and an electrochemical sensor for ozone (O3) (Alphasense OX-B431). The aim of this work is to explore the variance of the aforementioned sensors and how this variability can be used to optimize the measurements of low-cost electrochemical sensors, closer to real ones. The analysis is conducted by employing diagrams, boxplot and violin curves of the groups of sensors used, with satisfactory results.

Electrochem doi: 10.3390/electrochem4040035

Authors: Daniela Nunes da Silva Arnaldo César Pereira

Aptamers are three-dimensional structures of DNA or RNA that present high affinity and selectivity to specific targets, obtained through in vitro screening. Aptamers are used as biological recognizers in electrochemical biosensors, the so-called aptasensors, providing greater specificity in recognizing the most diverse analytes. Electrochemical aptasensors have extremely relevant characteristics, such as high sensitivity, low cost compared to other biorecognizers such as antibodies, and excellent compatibility, being considered one of the most promising alternative methods in several areas, such as biomedical diagnosis and monitoring environmental contaminants. In this sense, the present work reviews the relevant aspects of methodologies based on electrochemical aptasensors and their applications in determining antibiotics, seeking to foster innovation in electrochemical biosensors.