Oxygen Evolution Reaction Kinetics Research Articles

Cation Migration-Induced Lattice Oxygen Oxidation in Spinel Oxide for Superior Oxygen Evolution Reaction.

Activating the lattice oxygen can significantly improve the kinetics of oxygen evolution reaction (OER), however, it often results in reduced stability due to the bulk structure degradation. Here, we develop a spinel Fe0.3Co0.9Cr1.8O4 with active lattice oxygen by high-throughput methods, achieving high OER activity and stability, superior to the benchmark IrO2. The oxide exhibits an ultralow overpotential (190 mV at 10 mA cm-2) with outstanding stability for over 170 h at 100 mA cm-2. Soft X-ray absorption- and Raman-spectroscopies, combined with 18O isotope-labelling experiments, reveal that lattice oxygen activation is driven by Cr oxidation, which induces a cation migration from CrO6octahedrons toCrO4tetrahedrons. The geometry conversion creates accessible non-bonding oxygen states, crucial for lattice oxygen oxidation. Upon oxidation, peroxo O-O bond is formed and further stabilized by Cr6+ (CrO4 tetrahedra) via dimerization. This work establishes a new approach for designing efficient catalysts that feature active and stable lattice oxygen without compromising structural integrity.

Cation Migration‐Induced Lattice Oxygen Oxidation in Spinel Oxide for Superior Oxygen Evolution Reaction

Activating the lattice oxygen can significantly improve the kinetics of oxygen evolution reaction (OER), however, it often results in reduced stability due to the bulk structure degradation. Here, we develop a spinel Fe0.3Co0.9Cr1.8O4 with active lattice oxygen by high‐throughput methods, achieving high OER activity and stability, superior to the benchmark IrO2. The oxide exhibits an ultralow overpotential (190 mV at 10 mA cm–2) with outstanding stability for over 170 h at 100 mA cm–2. Soft X‐ray absorption‐ and Raman‐spectroscopies, combined with 18O isotope‐labelling experiments, reveal that lattice oxygen activation is driven by Cr oxidation, which induces a cation migration from CrO6 octahedrons to CrO4 tetrahedrons. The geometry conversion creates accessible non‐bonding oxygen states, crucial for lattice oxygen oxidation. Upon oxidation, peroxo O–O bond is formed and further stabilized by Cr6+ (CrO4 tetrahedra) via dimerization. This work establishes a new approach for designing efficient catalysts that feature active and stable lattice oxygen without compromising structural integrity.

Lewis acid sites in hollow cobalt phytate micropolyhedra promote the electrocatalytic water oxidation.

The acid-base microenvironment of the metal center is crucial for constructing advanced oxygen evolution reaction (OER) electrocatalysts. However, the correlation between acidic site and OER performance remains unclear for cobalt-based catalysts. Herein, Lewis acid sites in hollow cobalt phytate micropolyhedra (M-CoPA, M = Cu, Sr) were synthesized by a cation-exchange strategy, and their OER performances were studied systematically. Experimentally, Lewis acid Cu2+ sites with stronger Lewis acidity exhibited superior intrinsic activity and long-term stability in alkaline electrolytes. The spectroscopic and electrochemical studies show Lewis acid sites in hollow cobalt phytate micropolyhedra can modulate the electronic distribution of the adjacent cobalt center and further optimize the adsorption strength of oxygenated species. This study figures out the effect of Lewis acid sites on the OER kinetics and provides an effective way to develop high-efficiency electrocatalysts for energy conversion systems.

Enhanced oxygen evolution reaction in flexoelectric thin-film heterostructures

Recently, the flexoelectric effect has triggered considerable interest in energy-related applications, such as flexo-actuation, flexo-photovoltaic, and flexo-catalysis, because of its ubiquitous feature allowing the creation of electric polarity, i.e., the flexoelectric polarization (Pflexo), in non-polar materials by strain gradient. Here, we show a flexoelectric strategy in electrocatalytic water splitting. Remarkably enhanced oxygen evolution reaction (OER) properties are achieved in strain-gradient LaFeO3 (LFO) thin-film heterostructures owing to the promotion of kinetic processes by Pflexo. The improved OER is demonstrated by increased current density of ∼300% in linear sweep voltammetry and lowered charge transfer resistance by two orders of magnitude in electrochemical impedance spectroscopy. These are ascribed to the flexoelectric-induced downward bending of the LFO band, as revealed by density functional theory calculations and band structure measurements. With Pflexo in the thin-film heterostructure catalysts, the adsorption of hydroxyl ions is strengthened on the polar LFO surface, and the transfer of electrons is accelerated from the reactants/key intermediates to the catalyst across the band-tilted LFO layer. These findings indicate the significance of flexoelectric effect in OER kinetics and open a new perspective for exploiting catalytic mechanisms and performances in water splitting.

Synergy strategy of multi-metals confined in heteroatom framework toward constructing high-performance water oxidation electrocatalysts

The development of a low-cost, highly active, and non-precious metal catalyst for oxygen evolution reaction (OER) is of great significance. Multi-metallic catalysts containing Fe, Co, and Ni exhibit remarkable OER activity, while the specific contributions of each component and the synergistic effects in the ternary metal catalyst has remained elusive. In this work, we synthesized a series of S and N-doped mono-metallic, bi-metallic, and tri-metallic hollow carbon sphere electrocatalysts (M−SNC) with the goal of enhancing the catalysts OER activity and shedding light on the unique roles and synergistic effects of the various metals in the FeCoNi ternary metal catalyst. Our systematic analyses demonstrated the introduction of Fe effectively reduces the overpotential, Co accelerates the kinetics of OER, and the addition of Ni further improves the OER performance. Benefiting from the synergistic effects, the FeCoNi-SNC exhibits a low overpotential of 270 mV, with no morphological or structural changes after reaction, maintaining high activity for 72 h at 10 mA cm−2. Moreover, the assembled FeCoNi-SNC || Pt/C water electrolysis device operates for 65,000 s with minimal degradation, demonstrating its potential for practical application. This work presents a synergy strategy for the preparation of low-cost and highly efficient OER catalysts and further provides insights into the rational design and preparation of multicomponent catalysts.

Interfacial engineering to create ionically bonded heterostructures for ampere-level chlorine-free anodic reactions in seawater

Production of hydrogen directly from seawater can be a sustainable method; however, corrosive and competitive chlorine chemistry at the anode interfere with the oxygen evolution reaction (OER). Special materials need to be designed to avoid chlorine chemistry; hence, a two-dimensional metal-organic framework@WO3.B2O3 (MOF@WB) heterostructure with ionic bonds was engineered, which can deliver ~10x better performance and is ~65% more economical than commercial IrO2 for OER. Our system is stable in alkaline seawater for over 1000h without chlorine evolution and remains functional even after sitting idle for 5 days, making it integrable with renewable power sources. The catalyst also operated stably at the industrial-scale current density of 1.58Acm-2 for over 100h with 99% performance retention in alkaline seawater. Theoretical calculations reveal that B assists in the adsorption of the MOF on the WO3 substrate via the creation of ionic bonds, resulting in optimized surface geometries for selective reactions, which safeguard against chlorine chemistry. B2O3 helps modulate the B-OH sites at the interface via B-O-B bond hydrolysis, activating the OER kinetics, hence providing an ideal platform for effective direct seawater catalysis to produce low-cost hydrogen.

Tailoring of Electrocatalytic Oxygen Evolution Reaction Performance of 2D Conductive Co-Catecholate Metal-Organic Frameworks

Herein, we report the microwave hydrothermal synthesis of highly porous and conductive 2D Co-catecholate MOFs (Co-CATs) in the absence (Co-CAT-WO) and presence (Co-CAT-W) of N-methyl-2-pyrrolidone (NMP) polar solvent, and the study of these Co-CATs as electrocatalysts for oxygen evolution reaction (OER). The OER performance of Co-CAT-WO and Co-CAT-W is compared. The as-synthesized Co-CATs exhibit a 2D layered hexagonal structure. The electrical conductivity of Co-CAT-WO and Co-CAT-W is 6.9 and 5.8 S/m, respectively. The good conductivity and porous structure can initiate charge transport to achieve better OER performance under the 4e--transfer process. The as-prepared Co-CAT-WO and Co-CAT-W, respectively, show an overpotential of 455 and 424 mV at 10 mA/cm2 after performing the durability and chronoamperometry experiments for 13 h in 1M KOH. From the electrochemical studies, it is apparent that the Co-CAT-W exhibits better OER performance with low overpotential, high current density, and excellent stability over extended cycling. Moreover, the lower HOMO-LUMO gap for Co-CAT-W than that of the Co-CAT-WO endorses its better electrocatalytic activity. The post-OER results show that the Co-CAT-W electrocatalyst acts as a "precatalyst" rather than the original catalyst, and it undergoes electrochemical transformation to metal hydroxide and metal oxyhydroxide after the OER studies, promoting the OER kinetics. The findings of this work offer valuable insights into the synthetic strategies for developing 2D conducting metal-catecholate MOF catalysts for efficient and sustainable OER processes, which is crucial in water splitting for sustainable energy production.

Efficient electrocatalytic oxygen evolution enabled by porous Eu-Ni(PO3)2 nanosheet arrays

Phosphorous compounds have garnered significant interest as catalysts for the oxygen evolution reaction (OER). However, their catalytic performance often falls short, limiting their widespread application in electrocatalysis. The objective of this work is to improve the OER performance of nickel metaphosphate (Ni(PO3)2) by incorporating rare-earth europium (Eu). The prepared Eu-Ni(PO3)2 exhibits significant electron redistribution and features porous nanosheet arrays. The optimized Eu-Ni(PO3)2 exhibits outstanding OER activity, with an overpotential of 273 mV at 10 mA/cm, rapid OER kinetics with a Tafel slope of 39.4 mV/dec, and excellent electrochemical stability. These results surpass the performance of Ni(PO3)2, many reported Ni-based catalysts, and even commercial RuO2. Operando Raman spectroscopy reveals that the improvement of OER performance on Eu-Ni(PO3)2 is due to the accelerated formation of surface NiOOH active species and the enhanced interfacial water enrichment during OER. Density functional theory (DFT) calculations further demonstrate that Eu doping induces electronic modulation between the Eu sites and adjacent O-Ni sites, resulting in an optimized thermodynamic pathway with balanced adsorption energies for key oxygen intermediates, thus alleviating thermodynamic limitations during OER.

Tailoring Carrier Dynamics of BiVO4 Photoanode via Dual Incorporation of Au and Co(OH)x Cooperative Modification for Photoelectrochemical Water Splitting

AbstractPhotoelectrochemical solar to hydrogen production is a promising way to achieve carbon neutrality, but severe charge recombination in photoanodes limits the conversion efficiency. Herein, Au nanoparticles and Co(OH)x co‐sensitized bismuth vanadate (BiVO4) to construct AuCo(OH)x/BiVO4 photoanode for significantly enhancing the performance of photoelectrochemical water splitting. This process significantly improves the bulk charge carrier separation efficiency, the surface kinetics of water oxidation, and the electron density of BiVO4 photoanode through Au surface plasmon resonance (SPR) and Co(OH)x oxygen evolution catalysts effect. Additionally, the enhancement of the *O and the *OOH generation accelerate the oxygen evolution reaction kinetics. Consequently, the constructed AuCo(OH)x/BiVO4 photoanode demonstrates an excellent photocurrent of 6.2 mA cm−2 at 1.23 V versus reversible hydrogen electrode and a stable continuous output within 42 h. This work contributes to developing high‐efficiency and high‐stability photoanodes for solar H2 production through SPR effect and oxygen evolution catalysts.

Coordination Tuning of FeNi-HMT Frameworks Derived Effective Hybrid Catalysts for Water Oxidation.

FeNi-based hybrid materials are promising oxygen evolution reaction (OER) catalysts for water electrolysis in hydrogen generation. In this work, the coordination tuning of FeNi-HMT frameworks was achieved by simply changing the Fe/Ni ratios using hexamethylenetetramine (HMT) as an organic ligand, and the derived hybrid FeNi catalysts with varied compositions were probed for OER. Incorporating varying amounts of Fe3+ by adjusting the Ni/Fe ratio results in different metal-organic framework (MOF) structures, and higher Fe feed leads to the formation of amorphous structures due to the coordination structure destruction from the weaker coordination capacity of Fe3+ compared to Ni2+ combining with the tertiary amine ligand. Among them, the FeNi-HMT (with the Fe/Ni molar ratio of 1/1) derived catalyst, consisting of Fe0.36Ni0.64 alloy/Ni0.4Fe2.6O4 spinel oxide heterostructures supported by graphitized carbon matrix, exhibits the highest OER performance. The unique structure facilitates significant electron transfer at the alloy/spinel interface due to the large work function difference between each phase. This strong electronic effect downshifts the d-band center of the catalyst and optimizes the binding energies to the crucial oxygenated intermediates, thereby promoting the OER kinetics. This work highlights the importance of the coordination tuning of FeNi-HMT frameworks for highly efficient catalyst development.

Nanoflower-like NiCoFe layered hydroxide by in-situ electrochemical corrosion as highly efficient electrocatalyst for water oxidation

Layered double hydroxides have been widely applied for oxygen evolution reaction (OER) in the alkaline water electrolysis. However, the issues of poor connection between the catalyst and nickel foam and the specific mechanisms for active sites has not been fully documented. In this study, the in-situ nickel foam etching in a mixed solution of ferric chloride and cobalt nitrate at low temperatures was adopted for NiCoFe layered ternary hydroxides (NiCoFe LTHs) synthesis with a better tight integration. Physicochemical characterization indicated that the NiCoFe LTHs could grow directly through corroding nickel foam with a nano-flower-like morphology and structures. That is favorable for electron transfer from the catalytic layer to the conductive substrate. With the transition metal ions interaction and the tight integration construction, NiCo1Fe4-LTH-T60/NF presented an enhanced electrolysis performance with the overpotential of 234 mV (1.464 V vs. RHE) at current density of 100 mA cm−2 in 1 M KOH electrolyte. The Tafel slope for NiCo1Fe4-LTH-T60/NF electrode was 36.19 mV dec−1 for an enhanced OER kinetics. Besides, it demonstrated faster interfacial charge transfer process, better intrinsic electrochemical activity and stability in large current stability testing. It was revealed that the synergistic effect of the transition metal ions interaction enhancement and the mechanism of oxygen evolution elementary reaction for NiCo1Fe4-LTH-T60/NF during the water electrolysis by the electrochemical and theoretical calculation. This work provides theoretical basis and experimental support for the design and synthesis of future OER catalyst and substrate, which is significant for hydrogen and oxygen generation from water electrolysis.

Interface Engineering Induced by Low Ru Doping in Ni/Co@NC Derived from Ni-ZIF-67 for Enhanced Electrocatalytic Overall Water Splitting.

Electrochemical water splitting is a promising approach for hydrogen evolution reactions (HER); however, the oxygen evolution reaction (OER) remains a major bottleneck due to its high energy requirements. High-performance electrocatalysts capable of facilitating HER, OER, and overall water splitting (OWS) are highly needed to improve OER kinetics. In this work, we synthesized a trimetallic heterostructure of Ru, Ni, and Co incorporated into N-doped carbon (denoted as Ru/Ni/Co@NC) by first synthesizing Ni/Co@NC from Ni-ZIF-67 polyhedrons via high-temperature carbonization, followed by Ru doping using the galvanic replacement method. Benefiting from increased active surface sites, modulated electronic structure, and enhanced interfacial synergistic effects, Ru/Ni/Co@NC exhibited exceptional electrocatalytic performance for both HER and OER processes. The optimized Ru/Ni/Co@NC catalyst, with a minimal Ru mass ratio of ∼2.07%, demonstrated significantly low overpotential values of 34 mV for HER and 174 mV for OER at a current density of 10 mA/cm2 with corresponding Tafel slope values of 33.42 and 34.39 mV/dec, respectively. Further, the optimized catalyst was loaded onto carbon paper and used as anode and cathode materials for alkaline water splitting. Interestingly, a low cell voltage of just 1.44 V was obtained. The enhanced electrolytic performance was further elaborated by density functional theory (DFT) calculations, which confirmed that Ru doping in Ni/Co introduced additional active sites for H*, enhancing adsorption/desorption abilities for HER (ΔGH* = -0.30 eV), lowering water dissociation barrier (ΔGb = 0.49 eV) and reducing the energy barrier for the rate-determining step of OER (O* → OOH*) to 1.62 eV in an alkaline environment. These findings reflect the significant potential of ZIF-67-based catalysts in energy conversion and storage applications.

Interface Synergistic Effect of NiFe-LDH/3D GA Composites on Efficient Electrocatalytic Water Oxidation.

Currently, NiFe-LDH exhibits an excellent oxygen evolution reaction (OER) due to the interaction of the two metal elements on the layered double hydroxide (LDH) platform. However, such interaction is still insufficient to compensate for its poor electrical conductivity, limited number of active sites and sluggish dynamics. Herein, a feasible two-step hydrothermal strategy that involves coupling low-conductivity NiFe-LDH with 3D porous graphene aerogel (GA) is proposed. The optimized NiFe-LDH/GA (1:1) produced possesses a 257 mV (10 mA cm-2) overpotential and could operate stably for 56 h in an OER. Our investigation demonstrates that the NiFe-LDH/GA has a three-dimensional mesoporous structure, and that there is synergistic interaction between LDH and GA and interfacial reconstruction of NiOOH. Such an interface synergistic coupling effect promotes fast mass transfer and facilitates OER kinetics, and this work offers new insights into designing efficient and stable GA-based electrocatalysts.

Coupling multifunctional ZnCoAl-layered double hydroxides on Ti-Fe2O3 photoanode for efficient photoelectrochemical water oxidation

The efficiency of photoelectrochemical (PEC) water splitting is hindered by the slow kinetics of the oxygen evolution reaction (OER). This study developed a composite photoanode for water oxidation by incorporating ternary LDHs (ZnCoAl-LDH) onto Ti-Fe2O3 as a cocatalyst. The ZnCoAl-LDH/Ti–Fe2O3 photoanode achieved a photocurrent density of 3.51 mA/cm2 at 1.23 V vs. RHE, which is 9.8 times higher than that of bare Ti-Fe2O3. Through a series of characterizations, the synergistic effects among the three metals were revealed. Furthermore, the addition of Zn can induce the formation of more high-valent Co, increasing the conductivity of CoAl-LDH and significantly reducing the surface charge transfer resistance. These advantages significantly enhance the injection efficiency of ZnCoAl-LDH/Ti-Fe2O3 (82 %), thereby accelerating the OER kinetics of Ti-Fe2O3. Our work introduces new approaches for selecting photoelectrochemical cocatalysts and designing high-performance photoanodes for water splitting.

Regulating Local Coordination Sphere of Ir Single Atoms at the Atomic Interface for Efficient Oxygen Evolution Reaction.

Single-atom catalysts dispersed on an oxide support are essential for overcoming the sluggishness of the oxygen evolution reaction (OER). However, the durability of most metal single-atoms is compromised under harsh OER conditions due to their low coordination (weak metal-support interactions) and excessive disruption of metal-Olattice bonds to enable lattice oxygen participation, leading to metal dissolution and hindering their practical applicability. Herein, we systematically regulate the local coordination of Irsingle-atoms at the atomic level to enhance the performance of the OER by precisely modulating their steric localization on the NiO surface. Compared to conventional Irsingle-atoms adsorbed on NiO surface, the atomic Ir atoms partially embedded within the NiO surface (Iremb-NiO) exhibit a 2-fold increase in Ir-Ni second-shell interaction revealed by X-ray absorption spectroscopy (XAS), suggesting stronger metal-support interactions. Remarkably, Iremb-NiO with tailored coordination sphere exhibits excellent alkaline OER mass activity and long-term durability (degradation rate: ∼1 mV/h), outperforming commercial IrO2 (∼26 mV/h) and conventional Irsingle-atoms on NiO (∼7 mV/h). Comprehensive operando X-ray absorption and Raman spectroscopies, along with pH-dependence activity tests, identified high-valence atomic Ir sites embedded on the NiOOH surface during the OER followed the lattice oxygen mechanism, thereby circumventing the traditional linear scaling relationships. Moreover, the enhanced Ir-Ni second-shell interaction in Iremb-NiO plays a crucial role in imparting structural rigidity to Ir single-atoms, thereby mitigating Ir-dissolution and ensuring superior OER kinetics alongside sustained durability.

Synergistic effects of feni bimetal-doped biochar on oxygen evolution reaction kinetics: A one-step, low-temperature pyrolysis approach

As the hydrogen energy sector progresses, water electrolysis technology played a crucial role in producing green hydrogen. A major challenge in this endeavor lied in the oxygen evolution reaction (OER), where the overpotential has consistently been high leading to an increase in the energy demand. This study developed a one-step pyrolysis technique to transform metal-supported biomass into FeNi/NC catalysts having enhanced crystallinity and defect sites. This process without activation step using strong acids or bases reduced the operational procedures and the treatment of intermediate products, which reduced the technical difficulty. As the pyrolysis temperature increases, the metal ions in the biochar gradually formed stable metal oxides, which catalyze the alkaline OER and markedly boosted catalytic efficiency. Crucially, the abundance of lattice oxygen and oxygen vacancies in the catalyst played a key role in enhancing the OER kinetics. Notably, the catalyst pyrolyzed at 750 °C demonstrated good performance, with an overpotential of 270 mV at a concentration of 10 mA cm−2 of the density of current, which was superior to RuO2(η10=315 mV) and IrO2(η10=300 mV). Overall, this study reported an approach for the fabrication of high-performance OER catalysts and the strategic utilization of biomass resources for application in clean energy technologies.

Valence electronic engineering of hollow-nanocube-structured CoFeNi-layered double hydroxides for highly efficient oxygen evolution

The sluggish kinetics of oxygen evolution reaction (OER) and the high-cost of catalysts currently limit the large-scale industrialization of hydrogen production through water electrolysis, so developing efficient and inexpensive catalysts is a top priority. Herein, we employed a facile solvent method to synthesize a well-defined hollow nanocube-structured CoFeNi layered double hydroxide (LDH) with an optimized valence electronic structure of metal sites as an efficient electrocatalyst for accelerating the kinetics of OER. The optimal catalyst with the regulated valence electronic structure exhibited a strong synergistic catalytic effect and an excellent activity and stability. It achieved a lower overpotential of 294 mV at 100 mA cm−2, and high durability exceeding 100 h at 1 A cm−2, surpassing the performance of commercial Ir-/Ru-based catalysts. The optimized the coordination environment and valence electronic structure of metal sites can definitely serve as active centers for triggering OER, thereby improving the intrinsic electrocatalytic performance.

Boosting OER activity of Fe-N Moieties via Ni induced d-Orbital Tailoring for durable rechargeable Zn-Air batteries

Fe-N-C-based catalysts are considered the most promising Pt candidates due to their high oxygen reduction reaction (ORR) activity and low cost, whereas their oxygen evolution reaction (OER) performance is extremely poor due to the sluggish O-O coupling process, which hampers the practical application of rechargeable zinc-air batteries. Here, we in situ infiltrate Ni and Fe ions into metal triazolidine (MET)-derived N-doped porous carbon via a microporous confinement-pyrolysis strategy to enhance the OER activity of the Fe-N sites. The introduction of Ni induced the electronic delocalization of Fe atoms at the Fe-N center, which lowered the adsorption energy barriers for the decisive velocity step (O*→OOH*), thus accelerating the O-O bond coupling and OER kinetics. In addition, the preferential formation of NiOOH at high OER potentials ensures the catalytic stability of zinc-air batteries by trapping Fe ions escaping from carbon corrosion to form FeOOH. The optimized catalyst (FeNi-NC) has an overpotential of only 351 mV at a current density of 50 mA cm−2 under alkaline conditions. More importantly, the assembled ZABs can be stably charged and discharged for more than 500 h at 10 mA cm−2, demonstrating excellent battery charging and discharging stability. This work shows the great potential of strong electronic interactions between polymetals to improve Fe-N-C catalysts.

Rutile-structured high-entropy oxyfluorides: A platform for oxygen evolution catalysis

High-entropy (HE) design provides ample opportunities for accessing catalysts with unique physiochemical properties for advanced energy and environmental applications. Although a variety of multi-cationic high-entropy materials (HEMs) have been identified, HEMs consisted of multiple cationic and anionic elements are still limited. Herein, we present the design and synthesis of a series of rutile-structured high-entropy oxyfluorides (HEOFs), including [RuO2]x[MgMnZnCoF2]y, [MnO2]x[MgMnZnCoF2]y, [MoO2]x[MgMnZnCoF2]y, [SnO2]x[MgMnZnCoF2]y and [TiO2]x[MgMnZnCoF2]y (x:y = 3:1, 2:1, 1:1). All the HEOFs are obtained through mechanochemical alloying rutile-structured oxide and fluoride precursors and the HEOFs inherit the crystal structures of the skeleton oxides. Moreover, the HEOFs exhibit enhanced electrocatalytic oxygen evolution reaction (OER) activity than the corresponding one-element precursors. Typically, the best-performed HEOF [RuO2]3[MgMnZnCoF2]1 catalyst requires an overpotential of 240 mV to achieve a current density of 10 mA cm−2, which is lower than RuO2 (291 mV). More impressively, the specific mass activity of [RuO2]3[MgMnZnCoF2]1 is 537.1 A gRu−1 at 1.55 V (vs RHE), which is ca. 7.6 times that of RuO2 (70.5 A gRu−1). The enhanced electrocatalytic OER performance obtained on [RuO2]3[MgMnZnCoF2]1 is ascribed to the contribution of the different cationic and anionic elements that modulates the electronic structures of the pristine RuO2, which facilitates efficient OER kinetics. This work demonstrates the efficacy of high-entropy design towards approaching excellent catalysts for enhanced electrocatalysis.

Tailoring Ni-Fe-B Electronic Effects in Layered Double Hydroxides for Enhanced Oxygen Evolution Activity.

NiFe layered double hydroxides (LDHs) are state-of-the-art catalysts for the oxygen evolution reaction (OER) in alkaline media, yet they still face significant overpotentials. Here, quantitative boron (B) doping is introduced in NiFe LDHs (ranging from 0% to 20.3%) to effectively tailor the Ni-Fe-B electronic interactions for enhanced OER performance. The co-hydrolysis synthesis approach synchronizes the hydrolysis rates of Ni and Fe precursors with the formation rate of B─O─M (M: Ni, Fe) bonds, ensuring precise B doping into the NiFe LDHs. It is demonstrated that B, as an electron-deficient element, acts as an "electron sink" at doping levels from 0% to 13.5%, facilitating the transition of Ni2+ to the active Ni3+δ, thereby accelerating OER kinetics. However, excessive B doping (13.5-20.3%) effectively generates oxygen vacancies in the LDHs, which increases electron density at Ni2+ sites and hinders their transition to Ni3+δ, thereby reducing OER activity. Optimal OER performance is achieved at a B doping level of 13.5%, with an overpotential of only 208mV to reach a current density of 500mA cm-2, placing it among the most effective OER catalysts to date. This Ni-Fe-B electronic engineering opens new avenues for developing highly efficient anode catalysts for water-splitting hydrogen production.