Metal Electrocatalysts Research Articles

Room Temperature Synthesis of Gradient-Distributed Ni/Fe Sites in Layered Double Hydroxides for Enhanced Oxygen Evolution Reaction.

NiFe-based materials, especially NiFe layered double hydroxides (LDHs), are recognized as the most promising non-precious metal electrocatalysts for alkaline oxygen evolution reaction (OER). However, the precisely designed distribution of active sites for enhancing activities is still significantly restricted due to the lack of reasonable modulation strategies. Herein, sulfur doped Ni/Fe gradient-distributed LDH (GD-NiFe LDH/S) is fabricated by facile air-induced strategy at room temperature. This strategy accelerates the growth process with abundant CO2 and O2 in air, which promotes the inward migration of Fe species, resulting in gradient distribution with Ni/Fe-rich edge/planar. This allows significant enhancement of Ni/Fe synergistic effect, which plays a vital role in OER. Moreover, the sharp pine-like morphology of GD-NiFe LDH/S endows superhydrophilicity/aerophobicity characteristics, facilitating electrolyte penetrating and oxygen releasing. The optimized GD-NiFe LDH/S delivers superior OER performance with low overpotentials of 234 and 270mV at 10 and 100mA cm-2. The assembled anion exchange membrane water electrolyzer only requires 1.90V at 1.0 A cm-2 and 2.10V at 1.5 A cm-2 with robust stability for at least 130 h. This work introduces a facile air-induced strategy under room temperature to controllably design active site distributions of LDH for enhanced OER performance.

O−O Radical Coupling in Ultrathin Reconstructed Co6.8Se8 Nanosheets for Effective Oxygen Evolution and Zinc‐Air Batteries

AbstractDesigning ultrathin transition metal electrocatalysts with optimal surface chemistry state is crucial for oxygen evolution reaction (OER). However, the structure‐dependent electrochemical performance and the underlying catalytic mechanisms are still not clearly distinguished. Herein, we synthesize ultrathin Co6.8Se8 nanosheets (NSs) with subnanometer thickness by incorporating catalytically inactive selenium (Se) into ultrathin Co(OH)2, thereby switching the OER reaction pathway from adsorbate evolution mechanism (AEM) to oxide path mechanism (OPM). The prepared ultrathin Co6.8Se8 NSs exhibit an overpotential of 253 mV at 10 mA/cm2, outperforming the mostly reported Co‐based electrocatalysts. Advanced operando synchrotron spectroscopies and X‐ray absorption spectroscopy reveal the ultrathin Co6.8Se8 NSs, whose surface is reconstructed into Se‐doped Co(OH)2 during the OER process, could trigger direct O*−O* radical coupling rather than OOH* intermediates within AEM pathway thus lowering the energy input. Density functional theory calculations confirm that Co6.8Se8 NSs with shorter Co−Co bond length and stable Co−Se bond could optimize the rate‐determining step barrier via OPM pathway. Besides, rechargeable zinc‐air batteries based on Co6.8Se8 NSs exhibit excellent stability for more than 500 h of continuous charge–discharge cycles at 4 mA/cm2. The present study highlights the structural‐dependent switch of OER pathways and provides valuable insights for further development of ultrathin OER catalysts.

Enhanced H2O2 Production by Two-Electron Oxygen Reduction on Co3O4/MXene Catalyst

The two-electron oxygen reduction reaction (ORR) using an electrochemical method is considered a viable green technology for generating H2O2. Platinum group metals demonstrate excellent H2O2 generation performance due to their superior ORR activity and stability. However, the high cost of these electrocatalysts is a significant barrier to the widespread adoption of this technology, prompting research into non-precious metal catalysts as alternatives. In this work, Co3O4 nanoparticles with sized from 5 to 10 nm were synthesized on MXene sheets. Compared with Co3O4/C and MXene, the results indicated that Co3O4/MXene exhibited the best electrochemical performances, with an electron transfer number of ∼3.1 during oxygen reduction and an H2O2 selectivity of ∼47%. Co3O4/MXene also demonstrated great stability. After 5000 cycles, the H2O2 selectivity and electron transfer number remained at 50% and 3.0, respectively. After 12 h of continuous testing, Co3O4/MXene exhibited a high Faraday efficiency of 50% and H2O2 yield of 0.14 mol h−1 g−1, with H2O2 selectivity increasing to 68.7% and an electron transfer number of 2.6. The excellent electrochemistry is attributed to the synergistic effect between MXene and Co3O4. This study provides valuable insights into non-precious metal electrocatalysts for H2O2 generation.

Ni2+ Ion-Induced Phase and Morphology Tailoring in Nix-CuMoSe Nanorod Catalysts for Overall Water Splitting.

Copper molybdenum-based selenides (CuMoSe) as promising hydrogen evolution catalysts have been widely applied in the electrocatalytic splitting of water, while their limited active sites and relatively poor oxygen evolution activity restrict their further application as effective bifunctional electrocatalysts. Here, we report a simple hydrothermal method to fabricate rodlike NiCuMoSe arrays on nickel foam (Nix-CuMoSe/NF), the morphology of which is determined by Ni2+ ions because Ni2+ can promote the growth of the rodlike structure. Furthermore, the phase transformation from CuSe to CuSe2 is triggered by adjusting the Ni2+ ion content of the growth solution. Due to the morphology control and phase component modulation, the prepared Ni2.5-CuMoSe/NF possesses effective catalytic activities of the hydrogen/oxygen evolution reaction (HER/OER) with overpotentials of 89/183 mV at 10 mA cm-2 in 1 M KOH, and the cell (composed of Ni2.5-CuMoSe/NF as both the cathode and anode) can provide a current density of 10 mA cm-2 at a low cell voltage of 1.50 V with a stability of 110 h. This work will advance the development of transition metal electrocatalysts for effective overall water splitting.

Construction of core-shell NiFe LDH/Co(OH)F amorphous/crystalline heterostructure for synergistically enhanced electrocatalytic water oxidation

The development of high performance non-precious transition metal electrocatalysts for the oxygen evolution reaction (OER) is essential for the practical application of electrocatalytic water splitting. A promising strategy to prepare highly efficient and stable electrocatalysts for the OER can be achieved by constructing heterointerfaces between the amorphous and crystalline phases. Herein, a novel three-dimensional (3D) core-shell structured NiFe-LDH/Co(OH)F electrocatalyst on nickel foam (NF) with an amorphous/crystalline interface was achieved by growing 2D amorphous NiFe LDH nanosheets onto 1D crystalline Co(OH)F nanorod arrays using a simple two-step hydrothermal method. The resulting NiFe LDH/Co(OH)F/NF electrode exhibits outstanding electrochemical OER performance with an overpotential of 202 and 260mV at the current density of 10 and 100mAcm-2, a Tafel slope of 44.06mV dec-1, and an ultra-high stability over 100h at 300mAcm-2 without obvious degradation in 1M KOH. This research affords a new way to construct high-performance 3D hierarchical non-noble metal electrocatalysts for OER.

Salt template synthesis of CoO@Co nanoparticles encapsulated in 3D porous nitrogen‐doped carbon for oxygen reduction reaction

AbstractDeveloping high performance and cost‐effective electrocatalysts toward oxygen reduction reaction (ORR) is of critical significance for fuel cells and metal–air batteries. Herein, CoO@Co nanoparticles encapsulated in three‐dimensional (3D) porous nitrogen‐doped carbon (CoO@Co/Co‐N‐C) have been successfully derived from the cobalt–tannin framework via the NH4Cl salt template strategy. Owing to the generated NH3 and HCl gas from NH4Cl during the pyrolysis process, CoO@Co/Co‐N‐C formed a 3D porous carbon architecture with ultrahigh‐specific surface area (1052.5 m2 g−1). This hybrid catalyst exhibits comparable ORR catalytic activity, as well as superior stability to 20 wt% Pt/C in alkaline conditions. This finding offers a novel and facile strategy to synthesize 3D porous carbon as non‐precious metal electrocatalysts for energy conversion and storage applications.

In-situ engineering of 3D amorphous/crystalline NiFeP/NiMoP/NF composite for improved hydrogen evolution

Developing High-performance, low-cost, and non-noble-metal hydrogen evolution reaction (HER) electrocatalysts are one of the particularly significant elements to triumph over the slow kinetics of water dissociation. However, utilizing non-noble metal electrocatalysts at large-scale applications remains a significant challenge. This work informs the fabrication of porous amorphous NiFeP nanostructures on crystalline NiMoP/NF nanoflakes morphology via straightforward two-step electrodeposition and hydrothermal processes as a binder-free 3D hetero-structured composite catalyst for reliable HER. Based on experimental characterizations and density functional theory (DFT) calculations, the optimized NiFeP@NiMoP@NF electrocatalyst exhibits a favorable amorphous/crystalline morphology and an intrinsic metallic phase. This structure facilitates efficient charge transport and exposes abundant active sites with strong electronic interactions between NiFeP and NiMoP, significantly optimizing the adsorption and desorption energy of H2O and thus leading to easy adsorption of H and OH− on NiFeP@NiMoP and promoting the bubble release, finally improving electrocatalytic HER performance in alkaline media (only need an overpotential of 40 mV to conduct a current density of 10 mA cm−2). The rational and affordable developing technique in this study not only implies the importance of interface engineering in catalyst construction but also opens a new route for synthesizing high-efficiency Ni-based electrocatalysts for a variety of water electrolysis applications.

MoP assists the promotion on Fe2P and FeN4 for oxygen reduction and zinc-air battery

It is of great significance but remains challenging to simultaneously development cost-effective and efficient non-noble metal electrocatalysts (NNMEs) for oxygen reduction reaction (ORR) in both alkaline and acidic solutions. In current work, a multi-component synergism system is developed, which is comprised of molybdenum phosphide (MoP) shell onto iron phosphide clusters anchored on carbon matrixes that embedded with numerous FeN4 species (MoP/Fe2P-FeN4). The optimized MoP/Fe2P-FeN4 electrocatalyst delivers a synergistic enhancement in both alkaline and acidic ORR performances: E1/2: 0.885 V (0.1 M KOH electrolyte) and E1/2: 0.742 V (0.1 M HClO4 electrolyte). Furthermore, the equipped zinc-air batteries (ZABs) of MoP/Fe2P-FeN4 exhibit a power density of 140.6 mW cm−2@219.6 mA cm−2, which surpasses the corresponding Fe2P-FeN4 and commercial Pt/C catalyst. The computational calculations reveal that MoP/Fe2P-FeN4 shows a relative increase of d-band center closer to Fermin level than Fe2P-FeN4, tuning the rate-determining step to conversion of *O to *OOH intermediate, thus significant reducing the energy barrier and enhancing ORR activity. This strategy opens new opportunities to rational design of Fe-based nanocomposites for stimulated ORR and further ZAB activities.

Ionic liquid modifying conductivity and hydrophobicity of B4C for enhanced electrosynthesis of H2O2

Electrosynthesis of hydrogen peroxide (H2O2) via two-electron oxygen reduction reaction (2e− ORR) is an attractive energy-efficient and decentralized alternative to the conventional anthraquinone process. However, designing non-precious metal catalysts with high activity, selectivity and stability is a great challenge. Here, we report a facile and effective approach to improve the catalytic performance of commercial boron carbide (B4C) by loading ionic liquid (IL), which exploits the complementary properties of high electrical conductivity and hydrophobicity of IL. The B4C catalyst with optimal IL loading possesses the highest conductivity and O2 adsorption, exhibiting high H2O2 selectivity in both neutral (∼96 %) and alkaline (∼93 %) electrolyte, which are nearly ∼34 % and ∼19 % higher than pristine B4C, respectively. Moreover, its production rate is ∼1.5 times that of pristine B4C at 130 mA cm−2 current density, resulting in a high concentration of H2O2 (5.93 wt%) produced in flow-cell reactor. The long-term cycle test demonstrates the desirable stability of IL@B4C/GDE, which is attributed to the high hydrophobicity and tight bonding between IL@B4C and the substrate, giving a strong flood-proof capability at the three-phase interface and avoiding rapid flooding by the electrolyte. This work provides new insights into designing non-precious metal electrocatalysts for efficient electrosynthesis of H2O2, emphasizing the role of IL in interface engineering.

Leveraging interlocking structural defects of g-C3N4/CNT networks: Toward enhanced oxygen reduction activity of the cobalt-based electrocatalyst

Carbon-based transition-metal electrocatalysts are regarded as promising candidates for catalyzing oxygen reduction reaction (ORR), yet their electrocatalytic ORR performances are greatly limited by active sites utilization caused by the metal aggregation and pore collapse under high temperature. This study rationally designed a cobalt-based ORR catalyst supported on a g-C3N4/carbon nanotube (CNT) network as a cost-effective alternative of platinum-based catalysts. CNT were embedded into the lamellar precursor of melamine and cyanuric acid, and a synergistic effect between CNT and precursor was realized to regulate the density and activity of active sites. The polycondensation of precursors led to the formation of an "interlocking" structure of CNT supports with abundant exposed defects, allowing for effectively anchoring cobalt ions to generate Co-Nx sites. Meanwhile, partial Co ions underwent reconstruction and transportation to form Co nanoparticles and extended the disruptive CNT structure, exposing more interfacial defects to enhance the ORR catalytic properties. The prepared Co@g-C3N4/CNT catalyst demonstrated impressive ORR activity comparable to commercial Pt/C catalyst, showing superior stability. This research offers a promising approach for engineering interfacial defects to synthesize high-performance non-precious metal electrocatalysts for energy conversion applications.

Self‐Supported Metallic Alkaline Hydrogen Evolution Electrocatalysts Tolerant for Ampere‐Level Current Densities

AbstractElectrocatalytic water splitting is an attractive approach for large‐scale hydrogen generation, critical for global carbon neutrality. However, the prevalent commercialized alkaline water electrolysis is generally conducted at low current densities due to sluggish kinetics and high overpotential, severely hampering high‐efficiency hydrogen production. Exploration of hydrogen evolution reaction (HER) electrocatalysts that can reliably operate at ampere‐level current densities under low overpotentials is thus a primary challenge. In contrast to extensive studies using powdery electrocatalysts, the self‐supported metallic catalytic cathode has become a burgeoning direction toward ampere‐level current densities, owing to their integrated design with intensive interfacial binding, high conductivity and mechanical stability with industrial tolerance/adaption. Recent years have witnessed tremendous research advances in designing self‐supported metallic electrocatalysts. Therefore, this flourishing area is specially summarized. Beginning with the introduction to the theory and mechanism of alkaline HER, the engineering strategies on self‐supported metallic electrodes are systematically summarized, including metal and alloy construction, heterostructure engineering, doping manipulation, and surface design. Meanwhile, particular emphasis is focused on the relationship between structure, activity, and stability under ampere‐level HER. Finally, the existing challenges, requirements of industrial‐scale application, and future direction for designing electrocatalysts are summarized, aiming to provide a better solution for industrial alkaline water electrolysis.

Optimizing Hydrazine Activation on Dual‐Site Co‐Zn Catalysts for Direct Hydrazine‐Hydrogen Peroxide Fuel Cells

ABSTRACTDirect hydrazine‐hydrogen peroxide fuel cells (DHzHPFCs) offer unique advantages for air‐independent applications, but their commercialization is impeded by the lack of high‐performance and low‐cost catalysts. This study reports a novel dual‐site Co‐Zn catalyst designed to enhance the hydrazine oxidation reaction (HzOR) activity. Density functional theory calculations suggested that incorporating Zn into Co catalysts can weaken the binding strength of the crucial N2H3* intermediate, which limits the rate‐determining N2H3* desorption step. The synthesized p‐Co9Zn1 catalyst exhibited a remarkably low reaction potential of −0.15 V versus RHE at 10 mA cm−2, outperforming monometallic Co catalysts. Experimental and computational analyses revealed dual active sites at the Co/ZnO interface, which facilitate N2H3* desorption and subsequent N2H2* formation. A liquid N2H4‐H2O2 fuel cell with p‐Co9Zn1 catalyst achieved a high open circuit voltage of 1.916 V and a maximum power density of 195 mW cm−2, demonstrating the potential application of the dual‐site Co‐Zn catalyst. This rational design strategy of tuning the N2H3* binding energy through bimetallic interactions provides a pathway for developing efficient and economical non‐precious metal electrocatalysts for DHzHPFCs.

Developing Schottky high-controductivity Ti3C2TX MXene/Ni2P/NF heterojunction with modulating surface electron density to boost hydrogen evolution reaction

Nickel-based transition metal electrocatalysts for water electrolysis are promising alternatives to precious metal based electrocatalysts, due to their high activity, low cost, and relatively high stability, offering broad prospects for application in hydrogen production via water electrolysis. Modifying nickel-based transition metal electrocatalysts with phosphorus elements and Schottky heterojunction interfaces can influence the electronic state of the metal, thus enhance the electrocatalytic performance of the catalyst. In this study, a phosphor modified nickel-based electrocatalyst, i.e. MXene/Ni2P/NF electrode material was obtained by assembling Ni2P nanosheets on a nickel foam (NF) substrate and then depositing MXene nanosheets onto the surface of Ni2P/NF via electrophoretic deposition. Water droplets can wet the interior of the electrode material within 150 ms (below the detection limit), demonstrating excellent hydrophilicity, which facilitates the wettability of the electrolyte and the adsorption/desorption of reaction intermediates. Electrochemical tests revealed that the MXene/Ni2P/NF electrode exhibits an overpotential of only 94 mV at a current density of 10 mA cm−2, with a Tafel slope of 83.7 mV dec−1, in the hydrogen evolution reaction. The overpotential remains virtually unchanged after a 24-h stability test.

Ultra-fast synthesis of transition metal-MXene nanocomposite electrocatalyst for energy-saving seawater hydrogen production: Experiment and theory

Switching from the urea oxidation reaction (UOR) to the oxygen evolution reaction (OER) is a beneficial way to lower the amount of energy needed to make hydrogen gas during the hydrogen evolution reaction (HER). Due to the sluggish reaction kinetics of the six electrons reaction of UOR, designing a privileged bifunctional electrocatalyst for both HER and UOR necessitates. The 2D nano-sized non-noble metal electrocatalysts make it possible to speed up reactions and improve their electrocatalytic performance. We synthesized nickel-cobalt-MXene composite nanosheets (NiCoMXene) on the surface of copper foam using a one-pot, simple, and ultra-fast electrochemical method. This 2D electrocatalyst demonstrates high electrocatalytic performance towards HER (overpotential of 76 mV at −10 mA cm−2) with excellent durability in alkaline media. Furthermore, NiCoMXene nanocomposite served as a bifunctional electrocatalyst to investigate hydrogen gas production by a hybrid system HER coupled with UOR in seawater. The NiCoMXene requires a low overpotential for HER (81 mV) and UOR (1.38 V) to achieve a current density of 10 mA cm−2 in seawater, and the needed cell voltage to reach the same current density is 1.42 V in seawater. Our DFT analysis found a significant synergy between MXene and NiCo in the electrocatalyst. PDOS analysis showed remarkably that introducing Ni atoms to MXene shifts the d-band center to the left (lower energy), while Co atoms shifts it to the right (higher energy) and increased states near the Fermi level. This electronic structure makes the nanocomposite an ideal electrocatalyst, with MXene providing electrons and Co atoms serving as active sites for both HER and UOR.This research work can provide a useful directive to explore the electrocatalysts with outstanding catalytic activity.

Theoretical Investigation of Single-, Double-, and Triple- p-block Metals Anchored on g-CN Monolayer for Oxygen Electrocatalysis.

The design and development of highly active non-noble metal electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are crucial for metal-air batteries. In this work, the electrocatalytic performance of different p-block metal (PM = Sn, Sb, Pb and Bi) atoms embedded in the g-CN monolayer (PMx@g-CN, x = 1-3) for the OER and ORR was systematically investigated by density functional theory (DFT). The strong interaction between PMx atoms and g-CN substrates indicates the good stability of PMx@g-CN catalysts. Among all the designed catalysts, Bi3@g-CN is found to be a promising bifunctional electrocatalyst for both the OER and ORR with the calculated overpotential ηOER and ηORR of 0.23 and 0.25 V, respectively. With the atomic active sites of PMx increasing from x = 1 to 3, the OER and ORR catalytic activity is enhanced. The correlations between the overpotentials of the OER/ORR and Bader charge values of the anchored PMx atoms of the catalysts were established. Our findings contribute to searching for noble metal-free bifunctional electrocatalysts and shed light on the rational design of atomic active sites on electrocatalysts.

Visualizing the Structure and Dynamics of Transition Metal-Based Electrocatalysts Using Synchrotron X-Ray Absorption Spectroscopy.

As the global energy structure evolves and clean energy technologies advance, electrocatalysis has become a focal point as a critical conversion pathway in the new energy sector. Transitional metal electrocatalysts (TMEs) with their distinctive electronic structures and redox properties show great potential in electrocatalytic reactions. However, complex reaction mechanisms and kinetic limitations hinder the improvement of energy conversion efficiency, highlighting the necessity for comprehensive studies on structure and performance of electrocatalysts. X-ray Absorption Fine Structure (XAFS) spectra stand out as a robust tool for examining the electrocatalyst's structures and performance due to its atomic selectivity and sensitivity to local environments. This review delves into the application of XAFS technology in characterizing TMEs, providing in-depth analyses of X-ray Absorption Near-Edge Structure (XANES) spectra, and Extended XAFS (EXAFS) spectra in both R-space and k-space. These analyses reveal intrinsic structural information, electronic interactions, catalyst stability, and aggregation morphology. Furthermore, the paper examines advancements in in-situ XAFS techniques for real-time monitoring of active site changes, capturing critical intermediate and transitional states, and elucidating the evolution of active species during electrocatalytic reactions. These insights deepen our understanding on structure-activity relationship of electrocatalysts and offer valuable guidance for designing and developing highly active and stable electrocatalysts.

“Nanoregion” effect of ionic liquid mixture system for preparing highly active porous electrocatalytic hydrogen production materials

The development of porous electrocatalytic materials with high activity and large specific surface area is the key to realizing efficient hydrogen production by water electrolysis. In this paper, a universial strategy for preparing porous non-precious metal electrocatalysts with high effective surface area is provided based on the “nanoregion” formed by ionic liquid mixture system, and the feasibility is verified by constructing a porous NiCo@NC based electrocatalyst. The microstructure, surface composition, specific surface area and electrochemical properties of the porous electrocatalyst are investigated systematically. Compared with the traditional hydrothermal synthesis, the “nanoregion” effect can give the NiCo@NC electrocatalyst rich pore structure and good hydrophilicity, thus effectively improve the effective surface area available for the electrochemical reaction. As a result, the overpotential for HER on NiCo@NC-500 prepared in the ionic liquid mixing system is 113 mV lower than that on NiCo@NC-500-w prepared by common hydrothermal process, and the Tafel slope decreases by 37 mV dec−1 (33.9 %), further verifying the effectiveness of this simple and green strategy to develop porous non-precious metal electrocatalysts for hydrogen production by the “nanoregion” effect of ionic liquid mixture system.

Heterointerfacial engineering of N,P-doped carbon nanosheets supported Co/Co2P nanoparticles for boosting oxygen reduction and oxygen evolution reactions towards rechargeable Zn-air battery

Transition metal phosphides (TMPs) with high electrocatalytic activity for the oxygen evolution reaction (OER) are reckoned as a substitution of precious group metals catalysts in rechargeable Zn-air battery. In this work, Co/Co2P heterojunction nanoparticles supported N,P-doped carbon nanosheets (Co/Co2P@NPCNS) were designed and prepared via a facile one-step molten salt-assisted pyrolysis process. Density function theory calculations reveal that the heterogeneous interactions of Co/Co2P effectively enhance the bifunctional electrocatalytic activity for oxygen reduction reaction (ORR) and OER. The synergistic interaction between the Co/Co2P heterojunction nanoparticles with highly exposed active sites and excellent catalytic activity and the two-dimensional doped carbon nanosheets with high conductivity contributes to Co/Co2P@NPCNS exhibiting preeminent bifunctional ORR/OER activity and stability with a high half-wave potential for ORR (0.87 V), a low overpotential for OER (302 mV at 10 mA cm−2) and a low potential gap (0.66 V). The homemade rechargeable Zn-air battery performs high peak power density (187 mW cm−2) and exceptional endurance. This heterogeneous interface tactic of integrating TMPs with heteroatom-doped carbon materials may shed light on the research and development of non-precious metal electrocatalysts.

Non-Noble Metal Catalysts for Electrooxidation of 5-Hydroxymethylfurfural.

2,5-Furandicarboxylic acid (FDCA) is a class of valuable biomass-based platform compounds. The creation of FDCA involves the catalytic oxidation of 5-hydroxymethylfurfural (HMF). As a novel catalytic method, electrocatalysis has been utilized in the 5-hydroxymethylfurfural oxidation reaction (HMFOR). Common noble metal catalysts show catalytic activity, which is limited by price and reaction conditions. Non-noble metal catalyst is known for its environmental friendliness, affordability and high efficiency. The development of energy efficient non-noble metal catalysts plays a crucial role in enhancing the HMFOR process. It can greatly upgrade the demand of industrial production, and has important research significance for electrocatalytic oxidation of HMF. In this paper, the reaction mechanism of HMF undergoes electrocatalytic oxidation to produce FDCA are elaborately summarized. There are two reaction pathways and two oxidation mechanisms of HMFOR discussed deeply. In addition, the speculation on the response of the electrode potential to HMFOR is presented in this paper. The main non-noble metal electrocatalysts currently used are classified and summarized by targeting metal element species. Finally, the paper focus on the mechanistic effects of non-noble metal catalysts in the reaction, and provide the present prospects and challenges in the electrocatalytic oxidation reaction of HMF.

Modulating the D-Band Center of Electrocatalysts for Enhanced Water Splitting.

To tackle the global energy scarcity and environmental degradation, developing efficient electrocatalysts is essential for achieving sustainable hydrogen production via water splitting. Modulating the d-band center of transition metal electrocatalysts is an effective approach to regulate the adsorption energy of intermediates, alter reaction pathways, lower the energy barrier of the rate-determining step, and ultimately improve electrocatalytic water splitting performance. In this review, a comprehensive overview of the recent advancements in modulating the d-band center for enhanced electrocatalytic water splitting is offered. Initially, the basics of the d-band theory are discussed. Subsequently, recent modulation strategies that aim to boost electrocatalytic activity, with particular emphasis on the d-band center as a key indicator in water splitting are summarized. Lastly, the importance of regulating electrocatalytic activity through d-band center, along with the challenges and prospects for improving electrocatalytic water splitting performance by fine-tuning the transition metal d-band center, are provided.