Search Results (115)

In this study, a novel strategy to enhance the performance of palladium (Pd)-based catalysts by doping with metal oxides (Mn₃O₄, MoO₃, and SnO) has been developed in order to overcome the limitations of its low activity and high cost in the catalytic oxidation of formaldehyde (HCHO). The novelty of this strategy lies in the fact that by precisely controlling the types and doping ratios of the metal oxides, a significant enhancement of the electrochemical performance and catalytic activity of the Pd-based catalysts was achieved, while the dependence on precious metals was reduced and the cost-effectiveness of the catalysts was improved. The effects of different metal oxide doping on the catalytic performance were systematically investigated by electrochemical characterization and catalytic activity tests. Among the prepared catalysts, Pd-Mn₃O₄ showed the most excellent performance, with an electrochemically active surface area of 20.6 m²/g and a formaldehyde oxidation reaction (FOR) current density of 3.5 mA/cm², which were 31.6% and 169.2% higher than pure Pd, respectively. In a 1000 s timed current method stability test, the limiting current density of Pd-Mn₃O₄ reached 0.48 mA/cm², which is 4.4 times higher than that of pure Pd. The excellent catalytic performance is attributed to the abundant surface hydroxyl (-OH) groups provided by Mn₃O₄, which contribute to the oxidation of formaldehyde intermediates, as well as the electronic synergistic effect between Pd and Mn₃O₄, which is manifested as a 0.4 eV downshift of the Pd 3d binding energy. In addition, the sensor evaluation showed that the Pd-Mn₃O₄-based formaldehyde sensor exhibited a high sensitivity (1.5 μA/ppm), excellent linearity (R² = 0.995), minimal long-term degradation (<7% in 30 days), and ~20-fold selectivity for formaldehyde over interfering gases (e.g., ethanol). This study provides a theoretical basis and practical material reference for the development of efficient and low-cost catalysts for formaldehyde oxidation. Full article

In this work, we present the development and validation of an automated system for the Successive Ionic Layer Adsorption and Reaction (SILAR) method, aimed at depositing Cu₂ZnSnS₄ (CZTS) thin films. The system is based on a Raspberry Pi Pico microcontroller programmed in Micro-Python (Thonny 4.0.2), allowing precise control over immersion sequences, timing intervals, and substrate positioning along two degrees of freedom. Automation enhances reproducibility, safety, and reduces human error compared with manual operation. CZTS films were deposited on borosilicate glass and optically and structurally characterized. A gradual darkening of the films with increasing deposition cycles indicates controlled material accumulation. X-ray diffraction (XRD) and Raman spectroscopy confirmed the presence of CZTS phases, although with a partially amorphous structure. The estimated optical bandgap of ~1.34 eV is consistent with photovoltaic applications. These results validate the functionality of the automated SILAR platform for repeatable and scalable thin-film fabrication, offering a low-cost alternative for producing semiconductor absorber layers in solar energy technologies. Full article

Four silane-containing Schiff base oligomers (o-SBNs and o-SBBs) were synthesized by high-temperature polycondensation reactions using silicon-based dialdehydes with naphthalene and 1,1’-binaphthalene diamine derivates. The samples showed a moderate solubility in common organic solvents, where the incorporation of TPS cores into o-SBN2 allows the formation of highly soluble material in non-polar solvents with higher molecular weights (11.58 kDa) and polydispersity. All oligo-SBs displayed high thermal resistance (above 450 °C), showing enhanced thermal stability for TPS-containing oligomers, with the degradation temperature exceeding 530 °C (o-SBB2) and high T_g values due to the higher aromatic content granted by TPS and 1,1’-binaphthalene moieties. Optical results of the oligo-SBs showed broad absorption and emission behavior in the visible spectrum, ranging from deep blue (o-SBN1 and o-SBB1) to blue (o-SBN2 and o-SBB2). The structure promotes a clear bathochromic shift for TPS-based oligomers, attributed to an extended π-conjugation across the backbone. In addition, the π-π overlap effect highlights larger Stokes shifts for the DMS core oligomers o-SN2 (133 nm) and o-SBB1 (195 nm). The oligo-SBs were found to be wide-bandgap materials, with E_g^opt values in the range of 2.60 eV to 3.67 eV. The higher molecular weight of o-SBN2, which provided an extended π-conjugation, allows the lowest value of E_g^opt (2.60 eV) to be achieved. In addition, DFT, TDDFT and EDDM calculations were performed on trimeric oligo-SBs, revealing that HOMOs are localized in the amine-terminal fraction, while LUMOs are localized over the terminal aldehyde groups. These findings highlight the used DMS and TPS cores in Schiff base materials, providing valuable insights into fine-tuning physicochemical properties through the use of suitable building blocks and their potential as optoelectronic materials. Full article

Developing high-efficiency photoelectrodes plays an important role in the photoelectrocatalytic generation of hydrogen peroxide (H₂O₂) in the photoelectrochemical (PEC) water splitting field. In this work, an innovative strategy was proposed, the synergistic photocatalytic production of H₂O₂ using a bidirectional photoanode–photocathode coupling system under visible-light irradiation. Fe₂O₃-Ti, as the photoanode, which was built by way of Fe₂O₃ loaded on Ti-mesh using the hydrothermal-calcination method, was investigated in terms of the suitability of its properties for PEC H₂O₂ production after optimization of the bias voltage, the type of electrolyte solution, and the concentration of the electrolyte. Afterwards, a H-type double-electrode coupling system with an Fe₂O₃-Ti photoanode and a WO₃@Co₂SnO₄ photocathode was established for the bidirectional synergistic production of H₂O₂ under visible-light irradiation. The yield of H₂O₂ reached 919.56 μmol·L⁻¹·h⁻¹ in 2 h over −0.7 V with 1 mol·L⁻¹ of KHCO₃ as the anolyte and 0.1 mol·L⁻¹ Na₂SO₄ as the catholyte (pH = 3). It was inferred that H₂O₂ production on the WO₃@Co₂SnO₄ photocathode was in line with the 2e^- oxygen reduction reaction (ORR) principle, and on the Fe₂O₃-Ti photoanode was in line with the 2e^- water oxidation reaction (WOR) rule, or it was indirectly promoted by the electrolyte solution KHCO₃. This work provides an innovative idea and a reference for anode–cathode double coupling systems for the bidirectional production of H₂O₂. Full article

The co-addition of chromium (Cr) and tin (Sn) is known to enhance the wettability between copper (Cu) and graphite (C_gr), but the effect of Sn content remains poorly understood. This study aims to systematically investigate the influence of Sn content a (a = 0, 10, 20, 30, 40, 50, 80, 99 at. %) on the wettability, interfacial structure, surface/interface energy (σ_lv/σ_sl), and adhesion behavior of the Cu–aSn–1Cr/C_gr system at 1100 °C. The experimental results show that as the Sn content increases, the equilibrium contact angle (θ_e) of the metal droplet shows a non-monotonic trend; the thickness of the reaction product layer (RPL, consisting of Cr carbides (Cr_mC_n)) gradually increases, accompanied by a decrease in the calculated adhesion work ($W_{\mathrm{ad}}^{\mathrm{cal}}$). A “sandwich” interface structure is observed, consisting of two interfaces: metal||Cr_mC_n and Cr_mC_n||C_gr. Sn content mainly affects the former. At metal||Cr_mC_n, Sn exists in various forms (e.g., Cu–Sn solid solution, Cu_xSn_y compounds) in contact with Cr_mC_n. To elucidate the wetting and bonding mechanisms of metal||Cr_mC_n, simplified interfacial models are constructed and analyzed based on first-principles calculations of density functional theory (DFT). The trend of theoretically calculated results (σ_metal and W_ad) agrees with the experimental results (σ_lv and $W_{\mathrm{ad}}^{\mathrm{cal}}$). Further analysis of the partial density of state (PDOS) and charge density difference (CDD) reveals that charge distribution and bonding characteristics vary with Sn content, providing the microscopic insight into the nature of wettability and interfacial bonding strength. Full article

In the chlorination industry, the reactor is a crucial equipment in which the chlorination reaction takes place. However, when the reactor is subjected to complex conditions such as high temperatures (e.g., >200 °C) and high pressures (e.g., >10 MPa), its structural integrity is significantly compromised, leading to severe safety issues. In this study, the fatigue life of a reactor is analyzed, with particular focus on the fatigue behavior of the cyclone separator under varying working conditions, such as changes in the temperature, pressure, and chemical environment. Using finite element simulations under steady-state conditions and the S-N curve from fatigue testing, the fatigue life and potential weak points of the reactor under different amplitudes and vibration frequencies are analyzed and predicted. This analysis is conducted using a combined simulation approach with ABAQUS and Fe-Safe software, v 6.14. This work also considers the periodic vibrations at the base of the cyclone separator within the reactor. Fatigue simulations under different vibration conditions are performed to further assess the fatigue life of the reactor, providing a theoretical basis for the optimization of design and ensuring operational safety. In addition, the influence of welding zones on the fatigue life is discussed. The results indicate that the welding defects and stress concentration may cause the welded joint to become a critical weak point for fatigue failure. Therefore, the fatigue performance of the welding zone should be carefully considered during the design phase. Full article

In this study, a TiO₂/(MA)₂SnCl₄ nanocomposite film was synthesized using a sustainable, sunlight-driven approach, demonstrating enhanced photocatalytic performance for environmental remediation. TiO₂ nanoparticles (TiO₂-NPs) were dispersed in ethanol and mixed with a methylammonium (MA) and SnCl₂ precursor solution, followed by drop-casting onto a glass substrate and exposure to direct sunlight for 2 h. Sunlight served as an energy source, facilitating in situ structural modifications and leading to the formation of a well-integrated TiO₂/(MA)₂SnCl₄ hybrid structure, where TiO₂ was effectively encapsulated. Characterization revealed a band gap reduction from 3.1 eV (TiO₂-NPs) to 2.6 eV in the nanocomposite, extending light absorption into the visible range. The formation of Sn–O–Ti interactions enhanced charge separation, minimized electron–hole recombination, and improved charge carrier dynamics. Photocatalytic degradation tests using methylene blue (MB) under sunlight showed that the nanocomposite film achieved 90% MB degradation within 60 min, outperforming TiO₂-NPs, which achieved only 75% degradation. The presence of oxygen vacancies (OVs) generated during sunlight exposure further enhanced photocatalytic efficiency by acting as charge traps and reaction sites. This study introduces a green synthesis strategy leveraging sunlight as a renewable energy source, marking the first integration of (MA)₂SnCl₄ with TiO₂-NPs for enhanced photocatalysis. The synergistic effects of extended visible-light absorption, defect engineering, and efficient charge separation make TiO₂/(MA)₂SnCl₄ nanocomposite films a scalable, cost-effective solution for water purification applications, offering a promising solar-driven approach to addressing global water contamination challenges. Full article

The chemical transport method is a process that occurs naturally; however, it is also very useful in the chemical laboratory environment for the synthesis of inorganic crystals. It was successfully used for the syntheses of simple and complex inorganic compounds, from binary (e.g., ZnS, CdSe) to quaternary (e.g., Cu₂ZnSnS₄) compounds. Many experimental parameters influence the quality of products of chemical transport reactions, and among them, one may distinguish the used precursors and applied temperature gradient. The careful selection of experimental conditions is crucial for the production of high-quality crystals. Mathematical descriptions of the chemical transport phenomena, however, may potentially help in the design of proper conditions. Full article

The pursuit of electrochemical carbon dioxide reduction reaction (CO₂RR) as a means of energy generation and mitigation of global warming is of considerable interest. In this study, a novel RuO₂-incorporated SnO₂-fabricated glassy carbon electrode (GCE) with a Nafion binder was used for the electrochemical reduction of CO₂ in an aqueous alkaline imidazole medium. The electrode fabrication process involved the drop-casting method, where RuO₂.SnO₂ was incorporated onto the surface of the GCE. Electrochemical studies demonstrated that the GCE-RuO₂.SnO₂ electrode facilitated CO₂ reduction at −0.58 V vs. the reversible hydrogen electrode (RHE) via a diffusion-controlled pathway with the transfer of two electrons. Importantly, the first electron transfer step was identified as the rate-determining step (RDS). A Tafel slope of 144 mV dec⁻¹ confirmed the association of two-electron transfer kinetics with CO₂RR. Moreover, the standard rate constant (k_o) and formal potential (E°′) were evaluated as 2.89 × 10⁻⁵ cm s⁻¹ and 0.0998 V vs. RHE, respectively. Kinetic investigations also reveal that the deprotonation and electron release steps took place simultaneously in the CO₂RR. Based on the reported results, the GCE-RuO₂.SnO₂ electrode could be a promising candidate for CO₂ reduction, applicable in renewable energy generation. Full article

The development of state-of-the-art gas sensors based on metal oxide semiconductors (MOS) to monitor hazardous and greenhouse gas (e.g., methane, CH₄, and carbon dioxide, CO₂) has been significantly advanced. Moreover, the morphological and topographical structures of MOSs have significantly influenced the gas sensors by means of surface catalytic activities. This work examines the impact of morphological and topological networked assembly of zinc oxide (ZnO) nanostructures, including microparticles and nanoparticles (0D), nanowires and nanorods (1D), nanodisks (2D), and hierarchical networks of tetrapods (3D). Gas sensors consisting of vertically aligned ZnO nanorods (ZnO–NR) and topologically interconnected tetrapods (T–ZnO) of varying diameter and arm thickness synthesized using aqueous phase deposition and flame transport method on interdigitated Pt electrodes are evaluated for methane detection. Smaller-diameter nanorods and tetrapod arms (nanowire-like), having higher surface-to-volume ratios with reasonable porosity, exhibit improved sensing behavior. Interestingly, when the nanorods’ diameter and interconnected tetrapod arm thickness were comparable to the width of the depletion layer, a significant increase in sensitivity (from 2 to 30) and reduction in response/recovery time (from 58 s to 5.9 s) resulted, ascribed to rapid desorption of analyte species. Additionally, nanoparticles surface-catalyzed with Pd (~50 nm) accelerated gas sensing and lowered operating temperature (from 200 °C to 50 °C) when combined with UV photoactivation. We modeled the experimental findings using a modified general formula for ZnO methane sensors derived from the catalytic chemical reaction between methane molecules and oxygen ions and considered the structural surface-to-volume ratios (S/V) and electronic depletion region width (L_d) applicable to other gas sensors (e.g., SnO₂, TiO₂, MoO₃, and WO₃). Finally, the effects of UV light excitation reducing detection temperature help to break through the bottleneck of ZnO-based materials as energy-saving chemiresistors and promote applications relevant to environmental and industrial harmful gas detection. Full article

Solvents play a crucial role in ion–molecule reactions and have been used to control the outcome effectively. However, little is known about how solvent molecules affect atomic-level mechanisms. Therefore, we executed direct dynamics simulations of the HO⁻(H₂O_w) + CH₃CH₂Br system to elucidate the dynamics behavior of chemical reactions in a microsolvated environment and compared them with previous gas-phase data. Our results show that the presence of a single water solvent molecule significantly suppresses the direct mechanism, reducing its ratio from 0.62 to 0.18, thereby promoting the indirect mechanism. Spatial effects and prolonged ion–molecule collisions combine to drive this mechanism shift. Among them, water molecules impede the reactive collisions of HO⁻ and CH₃CH₂Br, while at the same time, the attractive interaction of hydrogen bonds between ions and molecules produces long-lived intermediates that favor the indirect mechanism. On the other hand, microsolvation also affects the reaction preference of the S_N2 and E2 channels, which is more conducive to stabilizing the transition state of the S_N2 channel due to the difference in solute–solvent interactions, thus increasing the competitiveness of this pathway. These results emphasize the profound influence of solvent molecules in regulating reaction selectivity and underlying microscopic mechanisms in more complex systems. Full article

This study provides a comprehensive structural, chemical, and optical characterization of CZTS thin films deposited on flexible Kapton substrates via the Successive Ionic Layer Adsorption and Reaction (SILAR) method. The investigation explored the effects of varying deposition cycles (40, 60, 70, and 80) and annealing treatments on the films. An X-ray diffraction (XRD) analysis demonstrated enhanced crystallinity and phase purity, particularly in films deposited with 70 cycles. These films exhibited a notable reduction in secondary phases in the as-deposited state, with further improvements observed after annealing at 400 °C and 450 °C in a sulfur atmosphere. A pole figure analysis indicates a decrease in texture disorder with annealing, suggesting improved crystalline orientation at higher temperatures. Field emission scanning electron microscopy (FE-SEM) showed enhancements in surface morphology, with increased grain size and uniformity post-annealing. Chemical uniformity was confirmed through Secondary Ion Mass Spectrometry (SIMS), Energy-Dispersive Spectroscopy (EDS), and X-ray Photoelectron Spectroscopy (XPS). XPS revealed the presence of CZTS phases alongside oxidized phases. Annealing effectively reduced secondary phases, such as ZnO, SnO₂, CuO, and SO₂, enhancing the CZTS phase. An optical analysis demonstrated that annealing at 200 °C in an air atmosphere reduced the band gap from 1.53 eV to 1.38 eV. In contrast, annealing at 400 °C and 450 °C in a sulfur atmosphere increased the band gap to 1.59 eV and 1.63 eV, respectively. The films exhibited p-type conductivity, as inferred from a valence band structure analysis. Density Functional Theory (DFT) calculations provided insights into the observed band gap variations, further substantiating the findings. Full article

Globalization has increased production in various industries, including textiles, food, and pharmaceuticals. These industries employ different dyes in production, leading to undesired discharge, which conventional treatment fails to remove from the water. The present study aims to synthesize, characterize, and use different pure catalysts (TiO₂ and Zn₂SnO₄) and their compounds doped with CoFe₂O₄ together with ozone (O₃) for the degradation of the azo dye yellow tartrazine (TZ), evaluating the process. For this characterization, N₂ porosimeter, zeta potential, X-ray diffraction, SEM-EDS, and diffuse reflectance spectra were used. Specific surface areas (m² g⁻¹) of 109, 106, 65, and 83 were used for TiO₂, CoFe₂O₄/TiO₂, Zn₂SnO₄, and CoFe₂O₄/Zn₂SnO₄, respectively. Both compounds are characterized as nanocatalysts as they have a band gap of 2.75 and 2.83 eV and average particle size of 98 and 85 nm for CoFe₂O₄/TiO₂ and Zn₂SnO₄, respectively. We employed a reactional model, which was able to describe the catalytic ozonation for all cases, with a low R² of 0.9731. The combination of processes increased TZ degradation from 57% to 74% compared to O₃ alone, achieving a maximum degradation of 98.5% within 50 min of catalysis at a low ozone flow rate. This highlights the potential of the produced catalysts for energy-efficient effluent treatment. Full article

In this research, we employed a high-entropy approach in tungsten-bronze-structured ferroelectric ceramics, preparing Sr_0.4Ba_0.6(Zr_0.2Ti_0.2Sn_0.2Ta_0.2Nb_0.2)₂ (denoted as SBN40-H) ceramics through the traditional solid-state reaction technique. By utilizing the high-entropy approach, the resulting SBN40-H ceramics demonstrated extremely fine grains, averaging 0.58 μm in size. Furthermore, these ceramics possessed a high bandgap of 3.35 eV, which, when combined with the small grain size, contributed to a remarkable breakdown strength of 570.01 kV/cm. The dielectric characteristics demonstrated typical relaxation behavior and outstanding temperature stability, with a capacitance temperature coefficient (TCC) of less than 5% within the temperature range of 111–317 °C. Additionally, the SBN40-H ceramics exhibit slim P–E loops with negligible hysteresis, which is considered to be related to the existence of weakly coupled relaxors. This results in exceptional overall energy-storage properties in the SBN40-H ceramics, exhibiting a notable recoverable energy density (W_rec) of 2.68 J/cm³ and an efficiency (η) of 93.7% at 390 kV/cm, and finally achieving a remarkable temperature stability in terms of energy-storage performance with variations in W_rec and η being less than 3.5% and 4.4% from 25 to 150 °C. It is worth noting that the high-entropy approach is highly effective in reducing grain size, increasing the breakdown field strength and enhancing the dielectric temperature stability of tungsten-bronze-structured ferroelectric ceramics. Full article

In this study, we synthesized perovskite Ba_0.4Sr_0.6SnO₃ ceramics with a unique thorn-like microstructure using the solid-state reaction method. The structural and complex dielectric properties were investigated in detail. X-ray diffraction was employed to characterize the phase purity, while X-ray photoelectron spectroscopy was used to analyze the chemical state of the components. The frequency and temperature dependence of the dielectric properties indicates that both the dielectric constant and loss are influenced by A-site ion doping as well as the presence of the thorn-like microstructure. The observed dielectric behavior can be explained by the interfacial polarization and dielectric relaxation processes, which arise from the existing Sn⁴⁺-Sn²⁺ pairs, oxygen vacancies, and defects with activation energies of 0.38 eV, 0.73 eV, and 0.54 eV, respectively. The resistances of grain boundaries, grains, and the thorn-like structure were revealed by the impedance spectra. These findings provide valuable insights into understanding structure–property relationships in perovskite stannate ceramics. Full article