Direct Electrocatalytic Methanol Oxidation on MoO3/Ni(OH)2: Exploiting Synergetic Effect of Adjacent Mo and Ni

Pairing N-Vacancy and Adjacent Ni-Sites in the Local Microenvironment to Regulate the Urea Oxidation Reaction Pathway With Enhanced Kinetics

The urea oxidation reaction (UOR) is a promising approach for replacing the oxygen evolution reaction in hydrogen production, offering lower energy consumption. However, the kinetics of Ni-based catalysts for UOR are hindered by the high formation potential of NiOOH and its repeated transition with Ni(OH)2. In this study, a local microenvironment featuring electron-deficient N-vacancies (VN) paired with adjacent electron-rich Ni-sites on Ni3N (Ni3N-VN) to enhance UOR kinetics is constructed. The electron-rich Ni-sites significantly reduce the energy barrier for NiOOH formation and promote the conversion of Ni(OH)2 to NiOOH. Meanwhile, the VN sites induce low charge transfer resistance in Ni3N, facilitating efficient electron transfer and boosting UOR performance while ensuring the stability of the active NiOOH phase. The VN sites promote the adsorption of the urea N atom at the active site, favoring the reaction pathway toward "NCO⁻" formation without requiring complete urea dissociation. This pathway alleviates the NiOOH/Ni(OH)2 conversion cycle, lowers charge transfer resistance, and improves reaction kinetics. Ni3N-VN demonstrates excellent UOR activity (low potential of 1.46 V at 1000 mA cm-2) and industrial prospects (integrating into an anion exchange membrane flow electrolyzer with 20% Pt/C, producing 600 mA cm-2 at 1.84 V), highlighting its potential for practical applications.

High-Entropy Metal Ammonium Phosphate Superstructure Nanocatalysts for Highly Efficient Water Oxidation and Methanol Oxidation

Electrochemical water splitting faces a major challenge due to the sluggish kinetics of the oxygen evolution reaction (OER). This study proposes an innovative strategy to replace OER with the thermodynamically favorable methanol oxidation reaction (MOR) while producing high-value formic acid. The study develops a novel series of metallic ammonium phosphate electrocatalysts (NPOs·nH2O) through a facile chemical precipitation method, including the high-entropy FeCoNiCuMn-NPO·nH2O. The unique superstructure coupled with multi-element synergy enables abundant active site exposure, optimized electronic configuration, and enhanced charge transfer capability. Remarkably, the high-entropy catalyst demonstrates exceptional bi-functional performance: achieving ultralow overpotentials of 204/289 mV at 10/100 mA cm-2 for OER, and requiring only 1.3 V versus RHE to deliver 10 mA cm-2 in MOR-assisted electrolysis. Particularly, it exhibits high normalized activity (electrochemically active surface area activity: 16.6 mA cm-2, mass activity: 980 mA mg-1) with 94% Faradaic efficiency for formic acid production. The catalyst maintains >120 h stability at industrial-level current density (100 mA cm-2), outperforming most reported transition metal-based electrocatalysts. This work establishes a new paradigm for designing high-entropy electrocatalysts through structural engineering and composition optimization, providing crucial insights for sustainable energy conversion and biomass valorization.

Electrocatalytic Conversion of Glucose into Renewable Formic Acid Using "Electron-Withdrawing" MoO3 Support under Mild Conditions

Electrocatalysis is a sustainable and effective approach to produce value-added chemical commodities from biomass, where highly effective catalyst is required. Since transition metal hydroxide is a feasible catalyst for electrochemical biomass conversion, rational optimization of its electrocatalytic activity is highly desired. Herein, electrocatalytic activity of glucose oxidation is significantly optimized by reducing the electron density at Ni active sites, which is achieved by depositing Ni(OH)2 at "electron-withdrawing" MoO3 support (Ni(OH)2MoO3-x). As results, the formation of active sites (NiOOH) and the adsorption of glucose are simultaneously facilitated in Ni(OH)2MoO3-x, which effectively converts glucose to formic acid (FA) with remarkable yield and Faraday efficiency (≈90.5 and 98%, respectively), far superior to conventional β-Ni(OH)2 catalyst (≈22.5 and 58.9%, respectively). In addition to a novel strategy for efficient FA production from glucose, this work offers valuable insights into the rational optimization of electrocatalytic oxidation of biomass-based substrates.

Electrospun Co-MoC Nanoparticles Embedded in Carbon Nanofibers for Highly Efficient pH-Universal Hydrogen Evolution Reaction and Alkaline Overall Water Splitting

The construction of highly efficient and self-supported electrocatalysts with abundant active sites for pH-universal hydrogen evolution reaction (HER) and alkaline water splitting is significantly challenging. Herein, Co and MoC nanoparticles embedded in nitrogen-doped carbon nanofibers (Co-MoC/NCNFs) which display a bamboo-like morphology are prepared by electrospinning followed by the carbonization method. The electrospun MoC possesses an ultrasmall size (≈5 nm) which can provide more active sites during electrocatalysis, while the introduction of Co greatly optimizes the electronic structure of MoC. Both endow the Co-MoC/NCNFs with superior HER performances over a wide pH range, with low overpotentials of 86, 116, and 145 mV to achieve a current density of 10 mA cm-2 in alkaline, acidic, and neutral media, respectively. Additionally, the catalyst exhibits remarkable alkaline oxygen evolution reaction (OER) activity with an overpotential of 254 mV to reach 10 mA cm-2. Density functional theory calculations confirm that electron transfer from Co to MoC regulates the adsorption free energy for hydrogen, thereby promoting HER. Moreover, an electrolyzer assembled with Co-MoC/NCNFs requires only a cell voltage of 1.59 V at 10 mA cm-2 in 1 m KOH. This work opens new pathways for the design of high-efficiency electrocatalysts for energy conversion applications.

Defect Engineering of Metal-Based Atomically Thin Materials for Catalyzing Small-Molecule Conversion Reactions

Recently, metal-based atomically thin materials (M-ATMs) have experienced rapid development due to their large specific surface areas, abundant electrochemically accessible sites, attractive surface chemistry, and strong in-plane chemical bonds. These characteristics make them highly desirable for energy-related conversion reactions. However, the insufficient active sites and slow reaction kinetics leading to unsatisfactory electrocatalytic performance limited their commercial application. To address these issues, defect engineering of M-ATMs has emerged to increase the active sites, modify the electronic structure, and enhance the catalytic reactivity and stability. This review provides a comprehensive summary of defect engineering strategies for M-ATM nanostructures, including vacancy creation, heteroatom doping, amorphous phase/grain boundary generation, and heterointerface construction. Introducing recent advancements in the application of M-ATMs in electrochemical small molecule conversion reactions (e.g., hydrogen, oxygen, carbon dioxide, nitrogen, and sulfur), which can contribute to a circular economy by recycling molecules like H2, O2, CO2, N2, and S. Furthermore, a crucial link between the reconstruction of atomic-level structure and catalytic activity via analyzing the dynamic evolution of M-ATMs during the reaction process is established. The review also outlines the challenges and prospects associated with M-ATM-based catalysts to inspire further research efforts in developing high-performance M-ATMs.

High Mass Transfer Rate in Electrocatalytic Hydrogen Evolution Achieved with Efficient Quasi-Gas Phase System

The adhesion of H2 bubbles on the electrode surface is one of the main factors limiting the performance of H2 evolution of electrolytic water, especially at high current density. To overcome this problem, here a "quasi-gas phase" electrolytic water reaction system based on capillary effect is proposed for the first time to improve the mass transfer efficiency of H2. The typical feature of this reaction system is that the main site of H2 evolution reaction is transferred from the bulk aqueous solution to the gas phase environment above the bulk aqueous solution, thus effectively inhibiting the aggregation of H2 bubbles and reducing the resistance of their diffusion away. Electrochemical test results show that the proposed quasi-gas phase system can significantly reduce the potential required in H2 evolution reaction process at high current density compared with the conventional electrolytic reaction system. Specifically, the overpotential potential is reduced by 0.31 V when the H2 evolution current density of 250 mA cm-2 is achieved.

Optimizing surface active sites via burying single atom into subsurface lattice for boosted methanol electrooxidation

The precise fabrication and regulation of the stable catalysts with desired performance still challengeable for single atom catalysts. Here, the Ru single atoms with different coordination environment in Ni3FeN lattice are synthesized and studied as a typical case over alkaline methanol electrooxidation. The Ni3FeN with buried Ru atoms in subsurface lattice (Ni3FeN-Ruburied) exhibits high selectivity and Faradaic efficiency of methanol to formate conversion. Meanwhile, operando spectroscopies reveal that the Ni3FeN-Ruburied exhibits an optimized adsorption of reactants along with an inhibited surface structural reconstruction. Additional theoretical simulations demonstrate that the Ni3FeN-Ruburied displays a regulated local electronic states of surface metal atoms with an optimized adsorption of reactants and reduced energy barrier of potential determining step. This work not only reports a high-efficient catalyst for methanol to formate conversion in alkaline condition, but also offers the insight into the rational design of single atom catalysts with more accessible surficial active sites.

Mn and Mo co-doped NiS nanosheets induce abundant Ni3+-O bonds for efficient electro-oxidation of biomass

MnMo-NiS were synthesized for electro-oxidizing ethylene glycol (EG), glycerol (GLY), and 5-hydroxymethylfurfural (HMF), achieving faradaic efficiencies of 97.5%, 98.6%, and 99.2%, and yield rates of 615.7, 475.5, and 333.9 μmol h-1 cm-2. In situ Raman spectroscopy and multi-step chronoamperometry reveal that Ni3+-O is the active site.

Ni3C/Ni3S2 Heterojunction Electrocatalyst for Efficient Methanol Oxidation via Dual Anion Co-modulation Strategy

Enhancing active states on the catalyst surface by modulating the adsorption-desorption properties of reactant species is crucial to optimizing the electrocatalytic activity of transition metal-based nanostructured materials. In this work, an efficient optimization strategy is proposed by co-modulating the dual anions (C and S) in Ni3C/Ni3S2, the heterostructured electrocatalyst, which is prepared via a simple hot-injection method. The presence of Ni3C/Ni3S2 heterojunctions accelerates the charge carrier transfer and promotes the generation of active sites, enabling the heterostructured electrocatalyst to achieve current densities of 10/100 mA cm-2 at 1.37 V/1.53 V. The Faradaic efficiencies for formate production coupled with hydrogen evolution approach 100%, accompanied with a stability record of 350 h. Additionally, operando electrochemical impedance spectroscopy (EIS), in situ Raman spectroscopy, and density functional theory (DFT) calculations further demonstrate that the creation of Ni3C/Ni3S2 heterointerfaces originating from dual anions' (C and S) differentiation is effective in adjusting the d-band center of active Ni atoms, promoting the generation of active sites, as well as optimizing the adsorption and desorption of reaction intermediates. This dual anions co-modulation strategy to stable heterostructure provides a general route for constructing high-performance transition metal-based electrocatalysts.

Pt1.8Pd0.2CuGa Intermetallic Nanocatalysts with Enhanced Methanol Oxidation Performance for Efficient Hybrid Seawater Electrolysis

Seawater electrolysis is a potentially cost-effective approach to green hydrogen production, but it currently faces substantial challenges for its high energy consumption and the interference of chlorine evolution reaction (ClER). Replacing the energy-demanding oxygen evolution reaction with methanol oxidation reaction (MOR) represents a promising alternative, as MOR occurs at a significantly low anodic potential, which cannot only reduce the voltage needed for electrolysis but also completely circumvents ClER. To this end, developing high-performance MOR catalysts is a key. Herein, a novel quaternary Pt1.8Pd0.2CuGa/C intermetallic nanoparticle (i-NP) catalyst is reported, which shows a high mass activity (11.13 A mgPGM -1), a large specific activity (18.13 mA cmPGM -2), and outstanding stability toward alkaline MOR. Advanced characterization and density functional theory calculations reveal that the introduction of atomically distributed Pd in Pt2CuGa intermetallic markedly promotes the oxidation of key reaction intermediates by enriching electron concentration around Pt sites, resulting in weak adsorption of carbon-containing intermediates and favorable adsorption of synergistic OH- groups near Pd sites. MOR-assisted seawater electrolysis is demonstrated, which continuously operates under 1.23 V for 240 h in simulated seawater and 120 h in natural seawater without notable degradation.

Nickel Hydroxide-Based Electrocatalysts for Promising Electrochemical Oxidation Reactions: Beyond Water Oxidation

Transition metal hydroxides have attracted significant research interest for their energy storage and conversion technique applications. In particular, nickel hydroxide (Ni(OH)2), with increasing significance, is extensively used in material science and engineering. The past decades have witnessed the flourishing of Ni(OH)2-based materials as efficient electrocatalysts for water oxidation, which is a critical catalytic reaction for sustainable technologies, such as water electrolysis, fuel cells, CO2 reduction, and metal-air batteries. Coupling the electrochemical oxidation of small molecules to replace water oxidation at the anode is confirmed as an effective and promising strategy for realizing the energy-saving production. The physicochemical properties of Ni(OH)2 related to conventional water oxidation are first presented in this review. Then, recent progress based on Ni(OH)2 materials for these promising electrochemical reactions is symmetrically categorized and reviewed. Significant emphasis is placed on establishing the structure-activity relationship and disclosing the reaction mechanism. Emerging material design strategies for novel electrocatalysts are also highlighted. Finally, the existing challenges and future research directions are presented.

High-Throughput Screening Strategy for Electrocatalysts for Selective Catalytic Oxidation of Formaldehyde to Formic Acid

Electrocatalytic oxidation of formaldehyde (FOR) is an effective way to prevent the damage caused by formaldehyde and produce high-value products. A screening strategy of a single-layer MnO2-supported transition metal catalyst for the selective oxidation of formaldehyde to formic acid was designed by high-throughput density functional calculation. N-MnO2@Cu and MnO2@Cu are predicted to be potential FOR electrocatalysts with potential-limiting steps (PDS) of 0.008 and -0.009 eV, respectively. Electronic structure analysis of single-atom catalysts (SACs) shows that single-layer MnO2 can regulate the spin density of loaded transition metal and thus regulate the adsorption of HCHO (Ead), and Ead is volcanically distributed with the magnetic moment descriptor -|mM - mH|. In addition, the formula quantifies Ead and |mM - mH| to construct a volcano-type descriptor α describing the PDS [ΔG(*CHO)]. Other electronic and structural properties of SACs and α are used as input features for the GBR method to construct machine learning models predicting the PDS (R2 = 0.97). This study hopes to provide some insights into FOR electrocatalysts.

Amorphous conversion in pyrolytic symmetric trinuclear nickel clusters trigger trifunctional electrocatalysts

The pursuit of multifunctional electrocatalysts holds significant importance due to their comprehension of material chemistry. Amorphous materials are particularly appealing, yet they pose challenges in terms of rational design due to their structural disorder and thermal instability. Herein, we propose a strategy that entails the tandem (low-temperature/250-350 °C) pyrolysis of molecular clusters, enabling preservation of the local short-range structures of the precursor Schiff base nickel (Ni3[2(C21H24N3Ni1.5O6)]). The temperature-dependent residuals demonstrate exceptional activity and stability for at least three distinct electrocatalytic processes, including the oxygen evolution reaction (η10 = 197 mV), urea oxidation reaction (η10 = 1.339 V), and methanol oxidation reaction (1358 mA cm-2 at 0.56 V). Three distinct nickel atom motifs are discovered for three efficient electrocatalytic reactions (Ni1 and Ni1' are preferred for UOR/MOR, while Ni2 is preferred for OER). Our discoveries pave the way for the potential development of multifunctional electrocatalysts through disordered engineering in molecular clusters under tandem pyrolysis.

Interfacial charge transfer in sheet Ni2P-FePx heterojunction to promote the study of electrocatalytic oxygen evolution

The substantial expense associated with catalysts significantly hampers the progress of electrolytic water-based hydrogen production technology. There is an urgent need to find non-precious metal catalysts that are both cost-effective and highly efficient. Here, the porous Ni2P-FePx nanomaterials were successfully prepared by hydrothermal method, nickel foam as the base, iron nitrate solution as the caustic agent and iron source, and finally phosphating at low temperature. The obtained porous Ni2P-FePx nanosheets showed excellent catalytic activity under alkaline PH = 14, and an overpotential of merely 241 mV was required to achieve a current density of 50 mA cm-2. The morphology of the nanosheet can still be flawlessly presented on the screen after 50 h of working at high current density.