Oxygen Evolution Reaction Research Articles

Iron‐Induced Localized Oxide Path Mechanism Enables Efficient and Stable Water Oxidation

The sluggish reaction kinetics of the anodic oxygen evolution reaction (OER) and the inadequate catalytic performance of non‐noble metal‐based electrocatalysts represent substantial barriers to the development of anion exchange membrane water electrolyzer (AEMWE). This study performed the synthesis of a three‐dimensional (3D) nanoflower‐like electrocatalyst (CFMO) via a simple one‐step method. The substitution of Co with Fe in the structure induces a localized oxide path mechanism (LOPM), facilitating direct O–O radical coupling for enhanced O2 evolution. The optimized CFMO‐2 electrocatalyst demonstrates superior OER performance, achieving an overpotential of 217 mV at 10 mA cm–2, alongside exceptional long‐term stability with minimal degradation after 1000 h of operation in 1.0 M KOH. These properties surpass most of conventional noble metal‐based electrocatalysts. Furthermore, the assembled AEMWE system, utilizing CFMO‐2, operates with a cell voltage of 1.65 V to deliver 1.0 A cm–2. In situ characterizations reveal that, in addition to the traditional adsorbate evolution mechanism (AEM) at isolated Co sites, a new LOPM occurred around the Fe and Co bimetallic sites. First‐principles calculations confirm the LOPM greatly reduced the energy barriers. This work highlights the potential of LOPM for improving the design of non‐noble metal‐based electrocatalysts and the development of AEMWE.

Amorphous IrOx nanoparticles on N-doped carbon matrix islands for enhancing proton exchange membrane water electrolysis

The development of an electrocatalyst and electrode that maintain their integrity under a high current density is vital for the advancement of PEMWE. In this context, we develop amorphous iridium oxide (IrOx) anchored on an N-doped carbon matrix island, directly formed on titanium porous transport layer through a simple method consisting of spray coating and pyrolysis. Remarkably, this configuration achieves 10 mA/cm2 current density for oxygen evolution reaction (OER) in acidic electrolyte, with only a 240 mV overpotential required, and the durability of this structure is confirmed by long-term and accelerated stress tests. These merits enable the unit cell to achieve over 6 A/cm2 at 2 V cell voltage without considerable degradation. This catalyst fulfills the requirement of the US Department of Energy’s 2026 target in performance (> 3 A/cm2 at 1.8 V) and in energy efficiency (> 65 %), as well as in the electricity cost for H2 production (US $2.0/kg H2).

Honeycomb‐Structured IrOx Foam Platelets as the Building Block of Anode Catalyst Layer in PEM Water Electrolyzer

AbstractAchieving robust long‐term durability with high catalytic activity at low iridium loading remains one of great challenges for proton exchange membrane water electrolyzer (PEMWE). Herein, we report the low‐temperature synthesis of iridium oxide foam platelets comprising edge‐sharing IrO6 octahedral honeycomb framework, and demonstrate the structural advantages of this material for multilevel tuning of anodic catalyst layer across atomic‐to‐microscopic scales for PEMWE. The integration of IrO6 octahedral honeycomb framework, foam‐like texture and platelet morphology into a single material system assures the generation and exposure of highly active and stable iridium catalytic sites for the oxygen evolution reaction (OER), while facilitating the reduction of both mass transport loss and electronic resistance of catalyst layer. As a proof of concept, the membrane electrode assembly in single‐cell PEMWE based on honeycomb‐structured IrOx foam platelets, with a low iridium loading (~0.3 mgIr/cm2), is demonstrated to exhibit high catalytic activity at ampere‐level current densities and to remain stable for more than 2000 hours.

High-Entropy Prussian Blue Analogue Derived Heterostructure Nanoparticles as Bifunctional Oxygen Conversion Electrocatalysts for the Rechargeable Zinc-Air Battery.

In response to energy challenges, rechargeable zinc-air batteries (RZABs) serve as an ideal platform for energy storage with a high energy density and safety. Nevertheless, addressing the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in RZAB requires highly active and robust electrocatalysts. High-entropy Prussian blue analogues (HEPBAs), formed by mixing diverse metals within a single lattice, exhibit enhanced stability due to their increased mixing entropy, which lowers the Gibbs free energy. HEPBAs innately enable sacrificial templating, an effective way to synthesize complex structures. Impressively, in this study, we successfully transform HEPBAs into exquisite multiphase (multimetallic alloy, metal carbide, and metal oxide) heterostructure nanoparticles through a controlled synthesis process. The elusive multiphase heterostructure nanoparticles manifested two active sites for selective ORR and OER. By integrating CNT into HEPBA-derived nanoparticles (HEPBA/CNT-800), the HEPBA/CNT-800 demonstrates superior activity toward both ORR (E1/2 = 0.77 V) in a 0.1 M KOH solution and the OER (η = 330 mV at 50 mA cm-2) in a 1 M KOH solution. The RZAB with a HEPBA/CNT-based air electrode demonstrated an open-circuit voltage of 1.39 V and provided a significant energy density of 71 mW cm-2. Moreover, the charge and discharge cycles lasting up to 40 h at a current density of 5 mA cm-2 demonstrate its excellent stability. This work provides an alternative avenue for the rational design of HEPBA's derivative for a sustainable rechargeable metal-air battery platform.

A Hypothesis on the Function of High‐Valent Fe in NiFe (Hydr)oxide in the Oxygen‐Evolution Reaction

This study investigated the dynamic changes in NiFe (hydr)oxide and identified the role of high‐valent Fe in the oxygen‐evolution reaction (OER) within alkaline media via in‐situ techniques. Several high‐valent Fe ions were found to remain considerably stable in the absence of potential in NiFe (hydr)oxide, even 96 hours after the OER. For Ni2+ hydroxide treated with 57Fe ions, where Fe sites are introduced onto the surface of Ni2+ hydroxide, no Fe4+ species were detected at the rate‐determining step (RDS). The findings of this study suggested that the oxidation of bulk Fe ions, similar to Ni ions, to high valent forms, is charge accumulation without a direct role in OER; these results offered a novel perspective on manipulating Fe states to optimize OER efficacy. The prevailing hypothesis suggested that trace amounts of high‐valent Fe ions, notably those on the surface, directly participate in OER.

A Hypothesis on the Function of High-Valent Fe in NiFe (Hydr)oxide in the Oxygen-Evolution Reaction.

This study investigated the dynamic changes in NiFe (hydr)oxide and identified the role of high-valent Fe in the oxygen-evolution reaction (OER) within alkaline media via in-situ techniques. Several high-valent Fe ions were found to remain considerably stable in the absence of potential in NiFe (hydr)oxide, even 96 hours after the OER. For Ni2+ hydroxide treated with 57Fe ions, where Fe sites are introduced onto the surface of Ni2+ hydroxide, no Fe4+ species were detected at the rate-determining step (RDS). The findings of this study suggested that the oxidation of bulk Fe ions, similar to Ni ions, to high valent forms, is charge accumulation without a direct role in OER; these results offered a novel perspective on manipulating Fe states to optimize OER efficacy. The prevailing hypothesis suggested that trace amounts of high-valent Fe ions, notably those on the surface, directly participate in OER.

Local compressive strain-induced anti-corrosion over isolated Ru-decorated Co3O4 for efficient acidic oxygen evolution

Enhancing corrosion resistance is essential for developing efficient electrocatalysts for acidic oxygen evolution reaction (OER). Herein, we report the strategic manipulation of the local compressive strain to reinforce the anti-corrosion properties of the non-precious Co3O4 support. The incorporation of Ru single atoms, larger in atomic size than Co, into the Co3O4 lattice (Ru-Co3O4), triggers localized strain compression and lattice distortion on the Co-O lattice. A comprehensive exploration of the correlation between this specific local compressive strain and electrocatalytic performance is conducted through experimental and theoretical analyses. The presence of the localized strain in Ru-Co3O4 is confirmed by operando X-ray absorption studies and supported by quantum calculations. This local strain, presented in a shortened Co-O bond length, enhances the anti-corrosion properties of Co3O4 by suppressing metal dissolutions. Consequently, Ru-Co3O4 shows satisfactory stability, maintaining OER for over 400 hours at 30 mA cm−2 with minimal decay. This study demonstrates the potential of the local strain effect in fortifying catalyst stability for acidic OER and beyond.

Honeycomb-Structured IrOx Foam Platelets as the Building Block of Anode Catalyst Layer in PEM Water Electrolyzer.

Achieving robust long-term durability with high catalytic activity at low iridium loading remains one of great challenges for proton exchange membrane water electrolyzer (PEMWE). Herein, we report the low-temperature synthesis of iridium oxide foam platelets comprising edge-sharing IrO6 octahedral honeycomb framework, and demonstrate the structural advantages of this material for multilevel tuning of anodic catalyst layer across atomic-to-microscopic scales for PEMWE. The integration of IrO6 octahedral honeycomb framework, foam-like texture and platelet morphology into a single material system assures the generation and exposure of highly active and stable iridium catalytic sites for the oxygen evolution reaction (OER), while facilitating the reduction of both mass transport loss and electronic resistance of catalyst layer. As a proof of concept, the membrane electrode assembly in single-cell PEMWE based on honeycomb-structured IrOx foam platelets, with a low iridium loading (~0.3 mgIr/cm2), is demonstrated to exhibit high catalytic activity at ampere-level current densities and to remain stable for more than 2000 hours.

One-step green synthesis of multi-morphological carbon nanotube forests for superior microwave absorption and electrocatalysis

Porous carbon materials with multiscale distinctive morphologies hold significant promise in electromagnetic wave stealth/protection and catalysis; however, formidable challenges are highly verbose and resource/time-consuming fabrication processes. Here, we report a one-step solvent/template-free self-expanding carbonization strategy for rapidly fabricating porous carbon foams (Ni/CNT) with zero-dimensional (0D) nanoparticles, one-dimensional (1D) nanotube forests, and three-dimensional (3D) hollow microvesicles. Owing to the multi-morphological structure and low-density feature, the resulting porous carbon foam Ni/CNT-800 achieves a minimum reflection loss of −56.48 dB and an effective bandwidth of 5.44 GHz at a low filler loading of only 9 wt%. Moreover, altering the electronic structure and surface chemistry of carbon foam by phosphorus doping enables a highly reduced durable overpotential (η) of 275 mV for oxygen evolution reaction. This work emphasizes a straightforward strategy for the facile design and efficient fabrication of carbon-based materials with unique multiscale porous morphologies, customizable functions, and various applications.

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 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.

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.

Bond engineering: weakening Ru–O covalency for efficient and stable water oxidation in acidic solutions

The persistent stability of ruthenium dioxide (RuO2) in acidic oxygen evolution reactions (OER) is compromised by the involvement of lattice oxygen (LO) and metal dissolution during the OER process. Heteroatom doping has been recognized as a viable strategy to foster the stability of RuO2 for acidic OER applications. This study presented an ion that does not readily gain or lose electrons, Ba2+, into RuO2 (Ba–RuO2) nanosheet (NS) catalyst that increased the number of exposed active sites, achieving a current density of 10 mA/cm2 with an overpotential of only 229 mV and sustaining this output for over 250 h. According to density functional theory (DFT) and X-ray absorption spectroscopy, Ba doping resulted in a longer Ru–O bond length, which in turn diminished the covalency of the bond. This alteration curtailed the involvement of LO and the dissolution of ruthenium (Ru), thereby markedly improving the durability of the catalyst over extended periods. Additionally, attenuated total reflectance-surface enhanced infrared absorption spectroscopy analysis substantiated that the OER mechanism shifted from a LO-mediated pathway to an adsorbate evolution pathway due to Ba doping, thereby circumventing Ru over-oxidation and further enhancing the stability of RuO2. Furthermore, DFT findings uncovered that Ba doping optimizes the adsorption energy of intermediates, thus enhancing the OER activity in acidic environments. This study offers a potent strategy to guide future developments on Ru-based oxide catalysts’ stability in an acidic environment.

Amorphous CoFePOx hollow nanocubes decorated with g-C3N4 quantum dots to achieve efficient electrocatalytic performance in the oxygen evolution reaction.

Simultaneously enriching active sites and enhancing intrinsic activity in a simple way is of great importance for the design of highly active electrocatalysts for the oxygen evolution reaction (OER), but it still faces challenges. Herein, g-C3N4 quantum dot decorated amorphous hollow CoFe bimetallic phosphate nanocubes (a-CoFePOx@CNQD) are prepared as an efficient OER electrocatalyst by a simple in situ etching-phosphating process. Research shows that their unique hollow architecture and amorphous structure can help provide generous exposed active sites for OER, and the incorporation of g-C3N4 quantum dots can effectively adjust the electronic structure to improve the intrinsic activity. Therefore, a-CoFePOx@CNQD exhibits excellent OER performance with a low overpotential (239 mV) at 10 mA cm-2 and a small Tafel slope (58.4 mV dec-1), surpassing the commercial RuO2. Furthermore, a-CoFePOx@CNQD as an electrode catalyst for a water electrolyzer and zinc-air battery also shows higher performance and stability than RuO2 + Pt/C catalysts. This study provides a feasible strategy for preparing efficient and stable amorphous hollow heterostructure OER electrocatalysts.

Porous and defective NiCo2O4 spinel derived from bimetallic NiCo-based Prussian blue analogue for enhanced hydrogen production via the urea electro-oxidation reaction

The efficient hydrogen production via overall water splitting is seriously restrained by the slow kinetics of the oxygen evolution reaction (OER). The substantially low potential for the urea electro-oxidation reaction (UOR) can tackle this problem by replacing the OER at the electrolyzer anode. Herein, the NiCo2O4 spinel with rich oxygen vacancies (Ov) and embedded within mesoporous carbon network (Ov-NiCo2O4@mC) was derived from NiCo-based Prussian blue analogous (NiCo PBA) and exploited as the bifunctional electrocatalyst of the UOR and OER for boost the hydrogen production via the overall water splitting. Benefiting to the regular skeleton and abundant dual metal sites of NiCo PBA, the derived Ov-NiCo2O4@mC comprises abundant oxygen vacancies, lattice defects, and adjustable electron structure. These features afford Ov-NiCo2O4@mC the improved UOR ability, showing the potential of 1.33 V versus reversible hydrogen electrode (RHE) at the current density of 10 mA cm−2, along with a small Tafel slopes of 31 mV dec-1, remarkably lower than that of the OER (1.51 V versus RHE, Tafel slope = 85 mV dec-1). The UOR performance of Ov-NiCo2O4@mC substantially outperforms to most of the reported Co and/or Ni-based electrocatalysts. Impressively, the assembled two-electrode urea-assisted overall water splitting device shows the small voltage for the hydrogen production (1.43 V versus RHE) and good long-term stability. The present work can provide a new alternative for the efficient hydrogen production using the MOFs-derivatives.

Dual-Doped Spinel Nickel-Iron Oxide Nanoflowers for Remarkably Enhanced Oxygen Evolution Reaction

The advancement of efficient electrocatalysts for the oxygen evolution reaction (OER) is essential for boosting electrochemical water splitting. Anionic double doping is a promising strategy to enhance catalytic efficiency through synergistic interactions among dopant elements. In this study, we synthesized a novel N/P anion co-doped NiFe2O4 electrocatalyst (N, P-NiFe2O4), featuring three-dimensional (3D) flower-like nanosheet. This material exhibits significant potential for applications in OER. The N, P-NiFe2O4 demonstrates exceptional performance with current density of 20mAcm-2 and 50mAcm-2 at low overpotential of only 220mV and 255mV, respectively. It has significantly reduced overpotentials of 109 and 162mV compared to undoped NiFe2O4. The superior catalytic activity of N, P-NiFe2O4 is attributed to the synergistic optimization of its electronic structure, surface morphology, and microstructure by anionic co-doping with N and P. Density functional theory (DFT) calculations further reveal that the dual doping with N and P ions effectively lowers the Gibbs free energy barrier associated with the critical *OH to *O transition in the OER process, thus accelerating the reaction kinetics and bolstering the intrinsic electrocatalytic activity. This study provides critical insights into the strategic design of high-efficiency, cost-effective OER electrocatalysts through targeted doping techniques, paving the way for the development of advanced materials for sustainable energy applications.

Influence of Annealing Temperature on the OER Activity of NiO(111) Nanosheets Prepared via Microwave and Solvothermal Synthesis Approaches.

Earth-abundant transition metal oxides are promising alternatives to precious metal oxides as electrocatalysts for the oxygen evolution reaction (OER) and are intensively investigated for alkaline water electrolysis. OER electrocatalysis, like most other catalytic reactions, is surface-initiated, and the catalyst performance is fundamentally determined by the surface properties. Most transition metal oxide catalysts show OER activities that depend on the predominantly exposed crystal facets/surface structure. Therefore, the design of synthetic strategies to obtain the most active crystal facets is of significant research interest. In this work, rock salt NiO OER catalysts with (111) predominantly exposed facets were synthesized by a solvothermal (ST) method either heated under supercritical or microwave-assisted (MW) conditions. Particular emphasis was placed on the influence of the post annealing temperature on the structural configuration and OER activity to compare their catalytic performances. The as-prepared electrocatalysts are pure α-Ni hydroxides which were converted to rock salt NiO (111) nanosheets with hexagonal pores after heat treatment at different temperatures. The OER activity of the electrodes has been evaluated in 0.1 M KOH using geometric and intrinsic current densities via normalization by the disk area and BET area, respectively. The lowest overpotential at a geometric current density of 10 mA/cm2 is found for samples pretreated by heating between 400 and 500 °C with a catalyst loading of 115 μg/cm2. Despite the very similar nature of the catalysts obtained from the two methods, the ST electrodes show a higher geometric and intrinsic current density for 500 °C pretreatment. The MW electrodes, however, achieve an optimal geometric current density for 400 °C pretreatment, while their intrinsic current density requires pretreatment over 600 °C. Interestingly, pretreated electrodes show consistently higher OER activity as compared to the poorly crystalline/less ordered hydroxide as-prepared electrocatalysts. Thus, our study highlights the importance of the synthesis method and pretreatment at an optimal temperature.

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.

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.

Wet sulfuration of molybdate and reconstruction regulation of trace Fe doping for oxygen evolution

There is a growing interest in the development of active, durable, and cost-effective electrocatalysts for oxygen evolution reactions (OER). In this study, we synthesized a self-reconstruction iron-doped sulfide-regulated nickel molybdate catalyst using wet chemical sulfuration and electrodeposition techniques. The core-shell nanorods (SC@NMO) were produced through rapid sulfuration. We investigated the effects of sulfur leaching on rapid and extensive electrochemical self-reconstruction. Our approach utilized the phase change of Fe3+ and electrodeposition-induced restructuring to enhance the catalyst's OER activity and stability in an alkaline electrolyte. Notably, iron ions establish a precipitation-dissolution dynamic equilibrium at the interface between the catalyst surface and the electrolyte, which minimizes iron loss and results in a more efficient and stable catalyst. The prepared sample, SC-Fe(Ni)OOH@NMO, demonstrated exceptional oxygen evolution performance and long-term stability in a 1 M KOH solution, achieving an overpotential of only 279 mV at a current density of 100 mA cm−2. It maintained stable operation for 200 h in a high-concentration 6 M KOH solution. The above data prove that this work provides a feasible strategy to enhance the OER catalytic capacity of metal oxides by the two modification methods of co-doping of metal and non-metal and reconstruction.