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Search Results (398)

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Keywords = catalytic transfer hydrogenation

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43 pages, 23033 KiB  
Review
MXene-Based Electrocatalysts for Water Splitting: Material Design, Surface Modulation, and Catalytic Performance
by Mohammad R. Thalji, Farzaneh Mahmoudi, Leonidas G. Bachas and Chinho Park
Int. J. Mol. Sci. 2025, 26(16), 8019; https://doi.org/10.3390/ijms26168019 - 19 Aug 2025
Abstract
Developing efficient and sustainable hydrogen production technologies is critical for advancing the global clean energy transition. This review highlights recent progress in the design, synthesis, and electrocatalytic applications of MXene-based materials for electrochemical water splitting. It discusses the fundamental mechanisms of the hydrogen [...] Read more.
Developing efficient and sustainable hydrogen production technologies is critical for advancing the global clean energy transition. This review highlights recent progress in the design, synthesis, and electrocatalytic applications of MXene-based materials for electrochemical water splitting. It discusses the fundamental mechanisms of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the structure–function relationships that govern electrocatalytic behavior. Emphasis is placed on the intrinsic structural and surface properties of MXenes, such as their layered architecture and tunable surface chemistry, which render them promising candidates for electrocatalysis. Despite these advantages, several practical limitations hinder their full potential, including oxidation susceptibility, restacking, and a limited number of active sites. Several studies have addressed these challenges using diverse engineering strategies, such as heteroatom doping; surface functionalization; and constructing MXene-based composites with metal chalcogenides, oxides, phosphides, and conductive polymers. These modifications have significantly improved catalytic activity, charge transfer kinetics, and long-term operational stability under various electrochemical conditions. Finally, this review outlines key knowledge gaps and emerging research directions, including defect engineering, single-atom integration, and system-level design, to accelerate the development of MXene-based electrocatalysts for sustainable hydrogen production. Full article
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13 pages, 7489 KiB  
Article
Interface Charge Transfer Engineering in NiFe Layered Double Hydroxide-Cs0.32WO3 Heterostructures for Enhanced Oxygen Evolution Reaction
by Ze Wang, Xinyu Song, Yue Liu, Zhiwang Sun, Xin Zhang, Yuanhao Wang and Shifeng Wang
Nanomaterials 2025, 15(16), 1255; https://doi.org/10.3390/nano15161255 - 14 Aug 2025
Viewed by 248
Abstract
Electrochemical water splitting for hydrogen production is considered a key pathway for achieving sustainable energy conversion. However, the sluggish reaction kinetics of the oxygen evolution reaction (OER) and high overpotentials severely hinder the large-scale application of water electrolysis technology. Nickel–iron layered double hydroxide [...] Read more.
Electrochemical water splitting for hydrogen production is considered a key pathway for achieving sustainable energy conversion. However, the sluggish reaction kinetics of the oxygen evolution reaction (OER) and high overpotentials severely hinder the large-scale application of water electrolysis technology. Nickel–iron layered double hydroxide (NiFe-LDH) has gained attention as a promising non-precious metal OER catalyst due to its abundant active sites and good intrinsic activity. However, its relatively low conductivity and charge transfer efficiency limit the improvement of catalytic performance. Therefore, this study used a simple hydrothermal method to generate a NiFe-LDH/Cs0.32WO3 heterojunction composite catalyst, relying on the excellent electronic conductivity of Cs0.32WO3 to improve overall charge transfer efficiency. According to electrochemical testing results, the modified NiFe-LDH/Cs0.32WO3-20 mg achieved a low overpotential of 349 mV at a current density of 10 mA cm−2, a Tafel slope of 67.0 mV dec−1, and a charge transfer resistance of 65.1 Ω, which represent decreases of 39 mV, 23.1%, and 40%, respectively, compared to pure NiFe-LDH. The key to performance improvement lies in the tightly bonded heterojunction interface between Cs0.32WO3 and NiFe-LDH. X-ray photoelectron spectroscopy (XPS) shows a distinct interfacial charge transfer phenomenon, with a notable negative shift of the W4f peak (0.85 eV), indicating the directional transfer of electrons from Cs0.32WO3 to NiFe-LDH. Under the influence of the built-in electric field within the heterojunction, this interfacial charge redistribution improved the electronic structure of NiFe-LDH, increased the proportion of high-valent metal ions, and significantly enhanced the OER reaction kinetics. This study provides new insights for the preparation of efficient heterojunction electrocatalysts. Full article
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13 pages, 5037 KiB  
Article
First-Principles Study of Sn-Doped RuO2 as Efficient Electrocatalysts for Enhanced Oxygen Evolution
by Caiyan Zheng, Qian Gao and Zhenpeng Hu
Catalysts 2025, 15(8), 770; https://doi.org/10.3390/catal15080770 - 13 Aug 2025
Viewed by 267
Abstract
Improving the catalytic performance of the oxygen evolution reaction (OER) for water splitting in acidic media is crucial for the production of clean and renewable hydrogen energy. Herein, we study the OER electrocatalytic properties of various active sites on four exposed (110) and [...] Read more.
Improving the catalytic performance of the oxygen evolution reaction (OER) for water splitting in acidic media is crucial for the production of clean and renewable hydrogen energy. Herein, we study the OER electrocatalytic properties of various active sites on four exposed (110) and (1¯10) surfaces of Sn-doped RuO2 (Sn/RuO2) with antiferromagnetic arrangements in acidic environments. The Sn/RuO2 bulk structure with the Cm space group exhibits favorable thermodynamic stability. The coordinatively unsaturated metal (Mcus) sites distributed on the right branch of the volcano plot are generally more active than the bridge-bonded lattice oxygen (Obr) sites located on the left. Different from the conventional knowledge that the most active site is located in the nearest neighbor of the doped atom, it has a lower OER overpotential when the active site is 3.6 Å away from the doped Sn atom. Among the sites studied, the 46-Rucus site exhibits the optimal OER catalytic performance. The inherent factors affecting the OER activity of each site on the Sn/RuO2 surface are further analyzed, including the center of the d/p band at the active sites, the average electrostatic potential of the ions, and the number of transferred electrons. This work provides a reminder for the selection of active sites used to evaluate catalytic performance, which will benefit the development of efficient OER electrocatalysts. Full article
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20 pages, 10780 KiB  
Article
Enhanced Photo-Fenton Removal of Oxytetracycline Hydrochloride via BP/Bi2MoO6 Z-Scheme Heterojunction Photocatalyst
by Jian Feng, Xiaohui Li, Xia Ran, Li Wang, Bo Xiao, Rong Li and Guangwei Feng
Int. J. Mol. Sci. 2025, 26(16), 7751; https://doi.org/10.3390/ijms26167751 - 11 Aug 2025
Viewed by 251
Abstract
Fenton oxidation technology utilizing hydrogen peroxide is recognized as an effective method for producing reactive oxygen species (ROS) to facilitate the degradation of antibiotics. However, the requirement for strongly acidic conditions during this process significantly restricts its broader applicability. In this study, we [...] Read more.
Fenton oxidation technology utilizing hydrogen peroxide is recognized as an effective method for producing reactive oxygen species (ROS) to facilitate the degradation of antibiotics. However, the requirement for strongly acidic conditions during this process significantly restricts its broader applicability. In this study, we synthesized black phosphorus (BP) nanosheets by exposing the {010} crystal planes and then constructed a 0D/2D BP/Bi2MoO6 (PBMO) heterojunction to function as a Fenton catalyst. The PBMO-75 heterojunction exhibited a remarkable increase in photo-Fenton catalytic activity towards oxytetracycline (OTC) under neutral conditions, achieving catalytic efficiencies that were 20 and 8 times greater than those of BP and Bi2MoO6 (BMO), respectively. This can be attributed to its strong absorption of visible light, the establishment of an internal electric field (IEF) at the interface, and the implementation of a Z-scheme catalytic mechanism. Additionally, the photo-Fenton system was further improved in OTC degradation through the continuous conversion of Mo6+/Mo5+ under visible light irradiation in conjunction with H2O2. Based on ERS, XPS, and active species trapping experiments, we propose a Z-scheme charge transfer mechanism for PBMO. This research offers compelling evidence that 0D/2D Z-scheme heterojunctions are promising candidates for the photo-Fenton treatment of antibiotic contaminants. Full article
(This article belongs to the Special Issue Latest Research in Photocatalysis)
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13 pages, 1717 KiB  
Article
High-Performance Hydrogen Gas Sensor Based on Pd-Doped MoS2/Si Heterojunction
by Enyu Ma, Zihao Xu, Ankai Sun, Shuo Yang and Jianyu Jiang
Sensors 2025, 25(15), 4753; https://doi.org/10.3390/s25154753 - 1 Aug 2025
Viewed by 349
Abstract
High-performance hydrogen gas sensors have gained considerable interest for their crucial function in reducing H2 explosion risk. Although MoS2 has good potential for chemical sensing, its application in hydrogen detection at room temperature is limited by slow response and incomplete recovery. [...] Read more.
High-performance hydrogen gas sensors have gained considerable interest for their crucial function in reducing H2 explosion risk. Although MoS2 has good potential for chemical sensing, its application in hydrogen detection at room temperature is limited by slow response and incomplete recovery. In this work, Pd-doped MoS2 thin films are deposited on a Si substrate, forming Pd-doped MoS2/Si heterojunctions via magnetron co-sputtering. The incorporation of Pd nanoparticles significantly enhances the catalytic activity for hydrogen adsorption and facilitates more efficient electron transfer. Owing to its distinct structural characteristics and sharp interface properties, the fabricated Pd-doped MoS2/Si heterojunction device exhibits excellent H2 sensing performance under room temperature conditions. The gas sensor device achieves an impressive sensing response of ~6.4 × 103% under 10,000 ppm H2 concentration, representing a 110% improvement compared to pristine MoS2. Furthermore, the fabricated heterojunction device demonstrates rapid response and recovery times (24.6/12.2 s), excellent repeatability, strong humidity resistance, and a ppb-level detection limit. These results demonstrate the promising application prospects of Pd-doped MoS2/Si heterojunctions in the development of advanced gas sensing devices. Full article
(This article belongs to the Special Issue 2D Materials for Advanced Sensing Technology)
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20 pages, 3586 KiB  
Article
Enhanced NiFe2O4 Catalyst Performance and Stability in Anion Exchange Membrane Water Electrolysis: Influence of Iron Content and Membrane Selection
by Khaja Wahab Ahmed, Aidan Dobson, Saeed Habibpour and Michael Fowler
Molecules 2025, 30(15), 3228; https://doi.org/10.3390/molecules30153228 - 1 Aug 2025
Viewed by 450
Abstract
Anion exchange membrane (AEM) water electrolysis is a potentially inexpensive and efficient source of hydrogen production as it uses effective low-cost catalysts. The catalytic activity and performance of nickel iron oxide (NiFeOx) catalysts for hydrogen production in AEM water electrolyzers were [...] Read more.
Anion exchange membrane (AEM) water electrolysis is a potentially inexpensive and efficient source of hydrogen production as it uses effective low-cost catalysts. The catalytic activity and performance of nickel iron oxide (NiFeOx) catalysts for hydrogen production in AEM water electrolyzers were investigated. The NiFeOx catalysts were synthesized with various iron content weight percentages, and at the stoichiometric ratio for nickel ferrite (NiFe2O4). The catalytic activity of NiFeOx catalyst was evaluated by linear sweep voltammetry (LSV) and chronoamperometry for the oxygen evolution reaction (OER). NiFe2O4 showed the highest activity for the OER in a three-electrode system, with 320 mA cm−2 at 2 V in 1 M KOH solution. NiFe2O4 displayed strong stability over a 600 h period at 50 mA cm−2 in a three-electrode setup, with a degradation rate of 15 μV/h. In single-cell electrolysis using a X-37 T membrane, at 2.2 V in 1 M KOH, the NiFe2O4 catalyst had the highest activity of 1100 mA cm−2 at 45 °C, which increased with the temperature to 1503 mA cm−2 at 55 °C. The performance of various membranes was examined, and the highest performance of the tested membranes was determined to be that of the Fumatech FAA-3-50 and FAS-50 membranes, implying that membrane performance is strongly correlated with membrane conductivity. The obtained Nyquist plots and equivalent circuit analysis were used to determine cell resistances. It was found that ohmic resistance decreases with an increase in temperature from 45 °C to 55 °C, implying the positive effect of temperature on AEM electrolysis. The FAA-3-50 and FAS-50 membranes were determined to have lower activation and ohmic resistances, indicative of higher conductivity and faster membrane charge transfer. NiFe2O4 in an AEM water electrolyzer displayed strong stability, with a voltage degradation rate of 0.833 mV/h over the 12 h durability test. Full article
(This article belongs to the Special Issue Water Electrolysis)
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7 pages, 1077 KiB  
Proceeding Paper
Synergistic Copper–Nickel-Doped Biochar from Animal Waste as Efficient Catalyst for Hydrogen Evolution Reaction
by Ala Al-Ardah, Zainab Baloochi, Yousra Kamal, Moza Al-Neama, Haya Suwaidan, Mostafa Selim and Noora Al-Qahtani
Mater. Proc. 2025, 22(1), 7; https://doi.org/10.3390/materproc2025022007 - 31 Jul 2025
Viewed by 124
Abstract
As the global energy industry shifts away from fossil fuels, there is a growing need for sustainable and renewable hydrogen production methods. This research investigates the potential of using biochar derived from animal waste as a precursor for creating effective catalysts for the [...] Read more.
As the global energy industry shifts away from fossil fuels, there is a growing need for sustainable and renewable hydrogen production methods. This research investigates the potential of using biochar derived from animal waste as a precursor for creating effective catalysts for the hydrogen evolution reaction (HER). By incorporating copper and nickel into the biochar through hydrothermal processing, the study examined the resulting catalysts’ structural, chemical, and catalytic properties. Techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) confirmed the successful integration of metallic nanoparticles and revealed notable changes in surface morphology, elemental composition, and functional group distribution. The Cu–Ni co-doped biochar catalyst (Cu–Ni/BC) demonstrated a significant 45% increase in hydrogen evolution efficiency compared to the undoped biochar control sample. These results highlight the synergistic effects of copper and nickel in enhancing the catalyst’s electron transfer capabilities and active site availability. This study offers a sustainable, cost-effective, and environmentally friendly alternative to conventional hydrogen production catalysts, presenting considerable potential for waste valorization while promoting clean energy solutions. The research aligns with circular economy principles, contributing to the advancement of sustainable energy technologies. Full article
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23 pages, 3019 KiB  
Review
Phase-Transfer Catalysis for Fuel Desulfurization
by Xun Zhang and Rui Wang
Catalysts 2025, 15(8), 724; https://doi.org/10.3390/catal15080724 - 30 Jul 2025
Viewed by 406
Abstract
This review surveys recent advances and emerging prospects in phase-transfer catalysis (PTC) for fuel desulfurization. In response to increasingly stringent environmental regulations, the removal of sulfur from transportation fuels has become imperative for curbing SOx emissions. Conventional hydrodesulfurization (HDS) operates under severe [...] Read more.
This review surveys recent advances and emerging prospects in phase-transfer catalysis (PTC) for fuel desulfurization. In response to increasingly stringent environmental regulations, the removal of sulfur from transportation fuels has become imperative for curbing SOx emissions. Conventional hydrodesulfurization (HDS) operates under severe temperature–pressure conditions and displays limited efficacy toward sterically hindered thiophenic compounds, motivating the exploration of non-hydrogen routes such as oxidative desulfurization (ODS). Within ODS, PTC offers distinctive benefits by shuttling reactants across immiscible phases, thereby enhancing reaction rates and selectivity. In particular, PTC enables efficient migration of organosulfur substrates from the hydrocarbon matrix into an aqueous phase where they are oxidized and subsequently extracted. The review first summarizes the deployment of classic PTC systems—quaternary ammonium salts, crown ethers, and related agents—in ODS operations and then delineates the underlying phase-transfer mechanisms, encompassing reaction-controlled, thermally triggered, photo-responsive, and pH-sensitive cycles. Attention is next directed to a new generation of catalysts, including quaternary-ammonium polyoxometalates, imidazolium-substituted polyoxometalates, and ionic-liquid-based hybrids. Their tailored architectures, catalytic performance, and mechanistic attributes are analyzed comprehensively. By incorporating multifunctional supports or rational structural modifications, these systems deliver superior desulfurization efficiency, product selectivity, and recyclability. Despite such progress, commercial deployment is hindered by the following outstanding issues: long-term catalyst durability, continuous-flow reactor design, and full life-cycle cost optimization. Future research should, therefore, focus on elucidating structure–performance relationships, translating batch protocols into robust continuous processes, and performing rigorous environmental and techno-economic assessments to accelerate the industrial adoption of PTC-enabled desulfurization. Full article
(This article belongs to the Special Issue Advanced Catalysis for Energy and a Sustainable Environment)
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12 pages, 2954 KiB  
Article
Electrochemical Hydrogenation of Furfural Enhancing Furfuryl Alcohol Selectivity over Flower-like Zn-Based MBON-2 in Alkaline Medium
by Yingxin Zhang, Hengxing Qiu, Chunyu Shen, Shuwen Hou, Qiuju Fu and Xuebo Zhao
Chemistry 2025, 7(4), 124; https://doi.org/10.3390/chemistry7040124 - 30 Jul 2025
Cited by 1 | Viewed by 348
Abstract
To address the low selectivity in the electrocatalytic conversion of furfural (FFR) to furfuryl alcohol (FFA) under alkaline conditions, a Zn-based metal–organic framework (MBON-2) featuring a 3D hierarchical flower-like architecture self-assembled from nanosheets was synthesized via a simple hydrothermal method. Under optimal conditions, [...] Read more.
To address the low selectivity in the electrocatalytic conversion of furfural (FFR) to furfuryl alcohol (FFA) under alkaline conditions, a Zn-based metal–organic framework (MBON-2) featuring a 3D hierarchical flower-like architecture self-assembled from nanosheets was synthesized via a simple hydrothermal method. Under optimal conditions, MBON-2 exhibited an extremely high selectivity of FFA (100%) and a high Faradaic efficiency (FE) of 93.19% at −0.2 V vs. RHE. Electrochemical impedance spectroscopy (EIS) revealed the excellent electron transfer and mass transport properties of MBON-2. In addition, in situ Fourier transform infrared (FTIR) spectroscopy studies confirmed the adsorption of FFR molecules onto the Zn and B sites of MBON-2 during the ECH of FFR, providing key insights into the hydrogenation mechanism. The numerous exposed B and Zn sites of the MBON-2, as well as its robust structural stability contributed to its outstanding catalytic performance in the electrochemical hydrogenation (ECH) of FFR. This work provides valuable guidelines for developing efficient Zn-based catalysts for the ECH of FFR. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass and Its Derivatives)
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11 pages, 2972 KiB  
Article
ZnCu Metal–Organic Framework Electrocatalysts for Efficient Ammonia Decomposition to Hydrogen
by Mingguang Ouyang, Geng Chen, Weitao Ning, Xiaoyang Wang, Xiaojiang Mu and Lei Miao
Energies 2025, 18(14), 3871; https://doi.org/10.3390/en18143871 - 21 Jul 2025
Viewed by 396
Abstract
The electrocatalytic decomposition of ammonia represents a promising route for sustainable hydrogen production, yet current systems rely heavily on noble metal catalysts with prohibitive costs and limited durability. A critical challenge lies in developing non-noble electrocatalysts that simultaneously achieve high active site exposure, [...] Read more.
The electrocatalytic decomposition of ammonia represents a promising route for sustainable hydrogen production, yet current systems rely heavily on noble metal catalysts with prohibitive costs and limited durability. A critical challenge lies in developing non-noble electrocatalysts that simultaneously achieve high active site exposure, optimized electronic configurations, and robust structural stability. Addressing these requirements, this study strategically engineered Cu-doped ZIF-8 architectures via in situ growth on nickel foam (NF) substrates through a facile room-temperature hydrothermal synthesis approach. Systematic optimization of the Cu/Zn molar ratio revealed that Cu0.7Zn0.3-ZIF/NF achieved optimal performance, exhibiting a distinctive nanoflower-like architecture that substantially increased accessible active sites. The hybrid catalyst demonstrated superior electrocatalytic performance with a current density of 124 mA cm−2 at 1.6 V vs. RHE and a notably low Tafel slope of 30.94 mV dec−1, outperforming both Zn-ZIF/NF (39.45 mV dec−1) and Cu-ZIF/NF (31.39 mV dec−1). Combined XPS and EDS analyses unveiled a synergistic electronic structure modulation between Zn and Cu, which facilitated charge transfer and enhanced catalytic efficiency. A gas chromatography product analysis identified H2 and N2 as the primary gaseous products, confirming the predominant occurrence of the ammonia oxidation reaction (AOR). This study not only presents a noble metal-free electrocatalyst with exceptional efficiency and durability for ammonia decomposition but also demonstrates the significant potential of MOF-derived materials in sustainable hydrogen production technologies. Full article
(This article belongs to the Special Issue Advanced Energy Conversion Technologies Based on Energy Physics)
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12 pages, 2577 KiB  
Article
Single-Atom Catalysts Dispersed on Graphitic Carbon Nitride (g-CN): Eley–Rideal-Driven CO-to-Ethanol Conversion
by Jing Wang, Qiuli Song, Yongchen Shang, Yuejie Liu and Jingxiang Zhao
Nanomaterials 2025, 15(14), 1111; https://doi.org/10.3390/nano15141111 - 17 Jul 2025
Viewed by 375
Abstract
The electrochemical reduction of carbon monoxide (COER) offers a promising route for generating value-added multi-carbon (C2+) products, such as ethanol, but achieving high catalytic performance remains a significant challenge. Herein, we performed comprehensive density functional theory (DFT) computations to evaluate CO-to-ethanol [...] Read more.
The electrochemical reduction of carbon monoxide (COER) offers a promising route for generating value-added multi-carbon (C2+) products, such as ethanol, but achieving high catalytic performance remains a significant challenge. Herein, we performed comprehensive density functional theory (DFT) computations to evaluate CO-to-ethanol conversion on single metal atoms anchored on graphitic carbon nitride (TM/g–CN). We showed that these metal atoms stably coordinate with edge N sites of g–CN to form active catalytic centers. Screening 20 TM/g–CN candidates, we identified V/g–CN and Zn/g–CN as optimal catalysts: both exhibit low free-energy barriers (<0.50 eV) for the key *CO hydrogenation steps and facilitate C–C coupling via an Eley–Rideal mechanism with a negligible kinetic barrier (~0.10 eV) to yield ethanol at low limiting potentials, which explains their superior COER performance. An analysis of d-band centers, charge transfer, and bonding–antibonding orbital distributions revealed the origin of their activity. This work provides theoretical insights and useful guidelines for designing high-performance single-atom COER catalysts. Full article
(This article belongs to the Section Theory and Simulation of Nanostructures)
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35 pages, 2722 KiB  
Review
Harnessing Ferrocene for Hydrogen and Carbon Dioxide Transformations: From Electrocatalysis to Capture
by Angel A. J. Torriero
Inorganics 2025, 13(7), 244; https://doi.org/10.3390/inorganics13070244 - 17 Jul 2025
Viewed by 579
Abstract
Ferrocene (Fc) is a redox-active organometallic scaffold whose unique electronic properties, stability, and modularity have enabled a broad range of catalytic and sensing applications. This review critically examines recent advances in Fc-based systems for hydrogen evolution and carbon dioxide (CO2) conversion, [...] Read more.
Ferrocene (Fc) is a redox-active organometallic scaffold whose unique electronic properties, stability, and modularity have enabled a broad range of catalytic and sensing applications. This review critically examines recent advances in Fc-based systems for hydrogen evolution and carbon dioxide (CO2) conversion, encompassing electrochemical, photochemical, and thermochemical strategies. Fc serves diverse functions: it operates as a reversible redox mediator, an electron reservoir, a ligand framework, and a structural modulator. Each role contributes differently to enhancing catalytic performance, improving selectivity, or increasing operational stability. We highlight how Fc integration facilitates proton-coupled electron transfer in hydrogen evolution, supports selective CO2 reduction in molecular and hybrid catalysts, and promotes efficient CO2 fixation and capture within functionalised frameworks. Emerging applications in electrosynthetic organic transformations are also discussed. Together, these findings position Fc as a foundational motif for designing future electrocatalytic and carbon management platforms. Full article
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26 pages, 5873 KiB  
Article
Pyridine–Quinoline and Biquinoline-Based Ruthenium p-Cymene Complexes as Efficient Catalysts for Transfer Hydrogenation Studies: Synthesis and Structural Characterization
by Nikolaos Zacharopoulos, Gregor Schnakenburg, Eleni I. Panagopoulou, Nikolaos S. Thomaidis and Athanassios I. Philippopoulos
Molecules 2025, 30(14), 2945; https://doi.org/10.3390/molecules30142945 - 11 Jul 2025
Viewed by 586
Abstract
Searching for new and efficient transfer hydrogenation catalysts, a series of new organometallic ruthenium(II)-arene complexes of the formulae [Ru(η6-p-cymene)(L)Cl][PF6] (18) and [Ru(η6-p-cymene)(L)Cl][Ru(η6-p-cymene)Cl3] ( [...] Read more.
Searching for new and efficient transfer hydrogenation catalysts, a series of new organometallic ruthenium(II)-arene complexes of the formulae [Ru(η6-p-cymene)(L)Cl][PF6] (18) and [Ru(η6-p-cymene)(L)Cl][Ru(η6-p-cymene)Cl3] (911) were synthesized and fully characterized. These were prepared from the reaction of pyridine–quinoline and biquinoline-based ligands (L) with [Ru(η6-p-cymene)(μ-Cl)Cl]2, in 1:2 and 1:1, metal (M) to ligand (L) molar ratios. Characterization includes a combination of spectroscopic methods (FT-IR, UV-Vis, multi nuclear NMR), elemental analysis and single-crystal X-ray crystallography. The pyridine–quinoline organic entities encountered, were prepared in high yield either via the thermal decarboxylation of the carboxylic acid congeners, namely 2,2′-pyridyl-quinoline-4-carboxylic acid (pqca), 8-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8-Mepqca), 6′-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (6′-Mepqca) and 8,6′-dimethyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8,6′-Me2pqca), affording the desired ligands pq, 8-Mepq, 6′-Mepq and 8,6′-Me2pq, or by the classical Friedländer condensation, to yield 4,6′-dimethyl-2,2′-pyridyl-quinoline (4,6′-Me2pq) and 4-methyl-2,2′-pyridyl-quinoline (4-Mepq), respectively. The solid-state structures of complexes 14, 6, 8 and 9 were determined showing a distorted octahedral coordination geometry. The unit cell of 3 contains two independent molecules (Ru-3), (Ru′-3) in a 1:1 ratio, due to a slight rotation of the arene ring. All complexes catalyze the transfer hydrogenation of acetophenone, using 2-propanol as a hydrogen donor in the presence of KOiPr. Among them, complexes 1 and 5 bearing methyl groups at the 8 and 4 position of the quinoline moiety, convert acetophenone to 1-phenylethanol quantitatively, within approximately 10 min with final TOFs of 1600 h−1. The catalytic performance of complexes 111, towards the transfer hydrogenation of p-substituted acetophenone derivatives and benzophenone, ranges from moderate to excellent. An inner-sphere mechanism has been suggested based on the detection of ruthenium(II) hydride species. Full article
(This article belongs to the Special Issue Advances in Coordination Chemistry, 3rd Edition)
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18 pages, 10208 KiB  
Article
Development of Ni-P-N-C/Nickel Foam for Efficient Hydrogen Production via Urea Electro-Oxidation
by Abdullah M. Aldawsari, Maged N. Shaddad and Saba A. Aladeemy
Catalysts 2025, 15(7), 662; https://doi.org/10.3390/catal15070662 - 7 Jul 2025
Viewed by 549
Abstract
Electrocatalytic urea oxidation reaction (UOR) is a promising dual-purpose approach for hydrogen production and wastewater treatment, addressing critical energy and environmental challenges. However, conventional anode materials often suffer from limited active sites and high charge transfer resistance, restricting UOR efficiency. To overcome these [...] Read more.
Electrocatalytic urea oxidation reaction (UOR) is a promising dual-purpose approach for hydrogen production and wastewater treatment, addressing critical energy and environmental challenges. However, conventional anode materials often suffer from limited active sites and high charge transfer resistance, restricting UOR efficiency. To overcome these issues, a novel NiP@PNC/NF electrocatalyst was developed via a one-step thermal annealing process under nitrogen, integrating nickel phosphide (NiP) with phosphorus and nitrogen co-doped carbon nanotubes (PNCs) on a nickel foam (NF) substrate. This design enhances catalytic activity and charge transfer, achieving current densities of 50 mA cm−2 at 1.34 V and 100 mA cm−2 at 1.43 V versus the reversible hydrogen electrode (RHE). The electrode’s high electrochemical surface area (235 cm2) and double-layer capacitance (94.1 mF) reflect abundant active sites, far surpassing NiP/NF (48 cm2, 15.8 mF) and PNC/NF (39.5 cm2, 12.9 mF). It maintains exceptional stability, with only a 16.3% performance loss after 35 h, as confirmed by HR-TEM showing an intact nanostructure. Our single-step annealing technique provides simplicity, scalability, and efficient integration of NiP nanoparticles inside a PNC matrix on nickel foam. This method enables consistent distribution and robust substrate adhesion, which are difficult to attain with multi-step or more intricate techniques. Full article
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35 pages, 3949 KiB  
Review
The Influence of Defect Engineering on the Electronic Structure of Active Centers on the Catalyst Surface
by Zhekun Zhang, Yankun Wang, Tianqi Guo and Pengfei Hu
Catalysts 2025, 15(7), 651; https://doi.org/10.3390/catal15070651 - 3 Jul 2025
Cited by 1 | Viewed by 934
Abstract
Defect engineering has recently emerged as a cutting-edge discipline for precise modulation of electronic structures in nanomaterials, shifting the paradigm in nanoscience from passive ‘inherent defect tolerance’ to proactive ‘defect-controlled design’. The deliberate introduction of defect—including vacancies, dopants, and interfaces—breaks the rigid symmetry [...] Read more.
Defect engineering has recently emerged as a cutting-edge discipline for precise modulation of electronic structures in nanomaterials, shifting the paradigm in nanoscience from passive ‘inherent defect tolerance’ to proactive ‘defect-controlled design’. The deliberate introduction of defect—including vacancies, dopants, and interfaces—breaks the rigid symmetry of crystalline lattices, enabling new pathways for optimizing catalysis performance. This review systematically summarizes the mechanisms underlying defect-mediated electronic structure at active sites regulation, including (1) reconstruction of the electronic density of states, (2) tuning of coordination microenvironments, (3) charge transfer and localization effects, (4) spin-state and magnetic coupling modulation, and (5) dynamic defect and interface engineering. These mechanisms elucidate how defect-induced electronic restructuring governs catalytic activity and selectivity. We further assess advanced characterization techniques and computational methodologies for probing defects-induced electronic states, offering deeper mechanistic insights at atomic scales. Finally, we highlight recent breakthroughs in defect-engineered nanomaterials for catalytic applications, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and beyond, while discussing existing challenges in scalability, defect stability, and structure–property causality. This review aims to provide actionable principles for the rational design of defects to tailor electronic structures toward next-generation energy technologies. Full article
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