Oxygen Evolution Reaction Process Research Articles

Enhanced water oxidation reaction by binder-free nickel oxide nanorod arrays electrocatalyst

Water splitting for hydrogen generation is one of the auspicious technologies for the sustainable resource storage and designing low cost electrocatalysts with high activity and is considerable to ameliorate the slow kinetic process of oxygen evolution reaction (OER). Accordingly, in this work, an experimental investigation for the improved water oxidation reaction based on the nickel oxide (NiO) nanorod arrays structure electrocatalyst is performed for the hydrogen production reaction. In this context, a highly efficient functional electrocatalyst is developed by morphology engineering for the growth of NiO nanorod arrays on Ni foam (NF) substrate (NiO–NF electrocatalyst) as an anode. The electrode is prepared by utilizing the hydrothermal method under the optimized experimental conditions (heating temperature of 100 °C and reaction time of 12 h in atmosphere). The electrochemical performance of the fabricated electrode is studied in an alkaline solution of 1.0 M KOH, and the obtained results revealed that only +350/+450 mV with/without iR-Correction is required to reach a current density of 100 mA cm−2, showing an effective electrocatalyst for water oxidation. The low charge-transfer resistance of the electrocatalyst (∼ 5 Ω) indicates favorable catalytic dynamics during OER. Notably, the electrocatalyst demonstrates outstanding durability during rigorous oxygen evolution testing in 1.0 M KOH for 100 h with ∼ 98% Faradaic efficiency. Additionally, the enhanced efficiency of the developed electrode for water splitting can be related to the improved morphology of the nanorod structure, high ordered array architecture, hydrophilic feature, and high adhesion of NiO nanorod arrays on the NF substrate.

Redox-active ligands enhance oxygen evolution reaction activity: Regulating the spin state of ferric ions and accelerating electron transfer

Metal-organic frameworks (MOFs) are considered as one of the most promising catalysts for oxygen evolution reaction (OER). However, only a few have introduced redox-active ligands into MOFs and explored their role in the OER process. In this work, we synthesized FeNi DHBQ/NF using the redox-active ligand 2,5-dihydroxy-1,4-benzoquinone (DHBQ), which exhibited excellent redox activity and required only 207 and 242 mV overpotentials to achieve current densities of 10 and 100 mA cm−2. Our research confirms that (i) the doping of Fe leads to the formation of Ni → O → Fe electron transfer channels in the MOFs and stronger electron transfer, attributed to the stronger d-π conjugation between the metal center and the ligand and reduced the d-orbital crystal field splitting energy of Fe3+; (ii) the rate determination step (RDS) in the OER process of the catalyst is the formation of O*, while Fe and redox-active ligands effectively regulate the adsorption energy of oxygen-containing intermediates, reducing the energy barrier of the RDS; (iii) the redox-active ligands can act as “electron reservoirs” in the electrochemical process, making Ni more readily oxidized to Ni3+ or even Ni4+ at low potentials, which is beneficial to the subsequent OER process.

Engineering of the crystalline state towards a defective state of CeCoO3 perovskite for the OER process in alkaline medium

Perovskite oxides act as an efficient electrocatalyst, but their limited active surface area has made it challenging to enhance their electrocatalytic activity. Thus, researchers found that changing the crystalline surface to an amorphous surface having oxygen vacancy can create an enriched active zone. In this research, we adopt a top-down approach for the amorphization of the crystalline CeCoO3 nanostructure that creates crystal defects, producing materials with a higher specific surface area, potential electrocatalysis for oxygen evolution reaction (OER) and greater stability. The calculated overpotential (η) and Tafel slope for defective CoCO3 (D-CCO3) is 265 and 35.95 mV dec−1 very low as compared to the crystalline CoCO3 (C-CCO3, 384 and 76.11 mV dec−1). The electrochemical analysis also suggests that the defective CoCO3 (D-CCO) exhibited the 33.96 mF and ECSA of 849 cm2. The current research enables a valuable approach for improving and changing the material properties and electrochemical efficiency of nanoscale perovskite oxide electrocatalysts attributed to crystal defects and nitrogen doping. However, further modifications to the D-CCO structure in the near future may be employed to address other environmental challenges.

Unraveling the Asymmetric O─O Radical Coupling Mechanism on Ru─O─Co for Enhanced Acidic Water Oxidation.

Heterogeneous oxides with multiple interfaces provide significant advantages in electrocatalytic activity and stability. However, controlling the local structure of these oxides is challenging. In this work, unique heterojunctions are demonstrated based on two oxide types, which are formed via pyrolysis of a ruthenocene metal-organic framework (Ru-MOF) at specific temperatures. The resulted Ru-MOF-400 exhibits excellent electrocatalytic activity, with an overpotential of 190mV at a current density of 10mA cm-2 in 0.1m HClO4 , and a mass activity of 2557 A gRu -1 , three orders of magnitude higher than commercial RuO2 . The Ru─O─Co bond formed by the incorporation of Co into the rutile lattice of RuO2 inhibits the disolution of Ru. Operando electrochemical investigations and density functional theory results reveal that the Ru-MOF-400 undergo asymmetric dual-active site oxide path mechanism during the acidic oxygen evolution reaction process, which is predominantly mediated by the asymmetric Ru─Co dual active site present at the interfaces between Co3 O4 and CoRuOx .

Development of SnCo2O4 spinel supported on the rGO nanosheet with the improved electrochemical performance of OER activity

Alkaline water electrolysis is a promising fuel cell technique that holds the potential for sustainable energy production. This process involves the generation of hydrogen and oxygen gases. Efforts have been focused on creating efficient catalysts utilizing readily available elements for the kinetically challenged process of oxygen evolution reaction (OER). For the enhancement of OER kinetics, we developed the SnCo2O4/rGO (SCO/rGO) nanohybrid via a hydrothermal route for the oxygen evaluation process performed under an alkaline solution (1.0 M KOH). The SCO/rGO exhibited diverse morphology, such as nanoparticles of SCO anchored on the rGO nanosheets that provide greater adsorption surface area for electrolyte ions. The electrocatalyst comprising of SCO/rGO nanohybrid exhibits superior performance compared to its SCO and rGO counterparts, as evidenced by its overpotential of 299 mV at 10 mA cm−2 and impressive durability of 50 h. Furthermore, the SCO/rGO nanohybrid display the lowest Tafel slope of 31.71 mV dec−1 than rGO (58.93 mV dec−1) and SCO (47.31 mV dec−1). Experimental data on active sites and high conductivity can be obtained through electrochemical impedance spectra (EIS) and electrochemical active surface area (ECSA), contributing to improved electrocatalytic results. The hybridization of a metal oxide (MOx) with a carbon derived substance presents a promising initial approach for manufacturing an outstanding catalyst for applications in water electrochemistry.

Reconstruction of CoNx /NC Catalyst during Oxygen Evolution Reaction by Fe3+ Modulation for Enhanced Activity and Stability.

The surface reconstruction of transition metal-based catalysts has been demonstrated to be beneficial for oxygen evolution reaction (OER). However, regulating the activity and stability of the components derived from reconstruction is challenging. Here, a strategy of Fe3+ ion modulating the reconstruction components of CoN0.4 on a nitrogen-doped carbon carrier(CoN0.4 /NC) electrocatalyst for promoted OER activity and stability is reported. During the OER process, the cobalt nitride components on the surface of CoN0.4 /NC catalyst were converted into CoOOH and Co4+ species. The addition of Fe3+ stabilized the CoOOH phase and facilitated the formation of Fe-CoOOH active phase, enhancing the activity and stability of CoN0.4 /NC. The Fe10 -CoN0.4 /NC catalyst achieved a current density of 10 mA cm-2 at a low overpotential of 300 mV (vs. RHE) with a Tafel slope of 68.12 mV dec-1 . The overpotential of Fe10 -CoN0.4 /NC was 122 mV lower than that of the CoN0.4 /NC catalyst and was comparable to commercial RuO2 catalyst. This study develops a novel technology for regulating the production of reconstructed species using Fe3+ ions.

Lattice tensile strain cobalt phosphate with modulated hydroxide adsorption and structure transformation towards improved oxygen evolution reaction

The adsorption energy of oxygen-containing intermediates for the oxygen evolution reaction (OER) electrocatalysts plays a key role on their electrocatalytic performances. Rational optimization and regulation of the binding energy of intermediates can effectively improve the catalytic activities. Herein, the binding strength of Co phosphate to *OH was weakened by generating lattice tensile strain via Mn replacement, which modulated the electronic structure and optimized the reactive intermediates adsorption with active sites. The tensile-strained lattice structure and stretched interatomic distance were confirmed by X-ray diffraction and extended X-ray absorption fine structure (EXAFS) spectra measurements. The as-obtained Mn-doped Co phosphate exhibits excellent OER activity with an overpotential of 335 mV at 10 mA cm−2, which is much higher than pristine Co phosphate. In-situ Raman spectra and methanol oxidation reaction experiments demonstrated that Mn-doped Co phosphate with lattice tensile strain shows optimized *OH adsorption strength, and is favorable to structure reconstruction and form highly active Co oxyhydroxide intermediate during OER process. Our work provides insight into the effects of the lattice strain on the OER activity from the standpoint of intermediate adsorption and structure transformation.

Magnetic Field-Enhanced Oxygen Evolution Reaction via the Tuneability of Spin Polarization in a Half-Metal Catalyst.

The magnetic field response of an electrochemistry process, such as the oxygen evolution reaction (OER), provides not only a strategy for enhanced catalytic activity by applying an external field but also a platform for revealing the functionality of the multiple degrees of freedom of the catalyst. However, the mechanism of the magnetic field tuneable OER is controversial. The strong correlation between the d and p orbitals of transition metal and oxygen still puzzles the dominant role of spin in an OER process. Here in this study, we have employed the manganite La0.7Sr0.2Ca0.1MnO3 as the ferromagnetic OER catalyst, which has a ferromagnetic/paramagnetic transition (TC) around the room temperature. It is found that the overpotential can be reduced by ∼18% after applying a 5 kOe magnetic field. Furthermore, this magnetic field can trigger a further improvement of the OER performance, and it demonstrates a strong temperature dependence which is incongruent with its magnetoresistive behavior. So our experiments suggest that the observed magnetic response originates dominantly from the triplet state of the O2, where the spin-polarized d and oxygen p orbitals lower the Gibbs free energy for every reaction step in OER. This study offers experimental evidence on comprehending the spin degree in the OER process, meanwhile benefiting the further design and engineering of the promising magnetic electrochemistry catalysts.

Directional Reconstruction of Iron Oxides to Active Sites for Superior Water Oxidation

AbstractRationally constructing and manipulating the in situ formed catalytically active surface of catalysts remains a tremendous challenge for a highly efficient water electrolysis. Herein, an anion and cation co‐induced strategy is presented to modulate in situ catalyst dissolution‐redeposition and to achieve the directional reconstruction of Zn and S co‐doped Fe2O3 and Fe3O4 on iron foams (Zn,S‐Fe2O3‐Fe3O4/IF), for oxygen evolution reaction (OER). Benefiting from Zn, S co‐doping and the presence of Fe3O4, a directionally reconstructed surface is obtained. The Fe2O3 in the Zn,S‐Fe2O3‐Fe3O4/IF is directionally reconstructed into FeOOH (Zn,S‐Fe3O4‐FeOOH/IF), in which the S leaching promotes the Fe dissolution and the Zn co‐deposition regulates the activity of the obtained FeOOH. Moreover, the presence of Fe3O4 provides a stable site for FeOOH deposition, and thus causes more FeOOH active components to be formed. Directionally reconstructed Zn,S‐Fe3O4‐FeOOH/IF outperformes many state‐of‐the‐art OER catalysts and demonstrates a remarkable stability. The experimental and density functional theory (DFT) calculation results show that the introduction of Zn‐doped FeOOH with abundant oxygen vacancies through directional reconstruction has activated lattice O atoms, facilitating the OER process on the heterojunction surface following the lattice oxygen mechanism (LOM) pathway. This work makes a stride in co‐induced strategy modulating directional reconstruction.

Exploring the mechanisms of catalytic performance enhancement for HER and OER on nickel film by incorporating antimony atoms: DFT study and experimental validation

The proper design of earth-abundant bifunctional electrocatalysts for best-performing water electrolysis is exceptionally challenging. Herein, we investigated the mechanism of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on nickel film by incorporating antimony atoms to realize its overall water splitting performance. Density functional theory (DFT) predictions demonstrate that the incorporation of antimony with a two-dimensional structure to the nickel backbone could optimize free energies of intermediates during HER and OER processes, thereby modulating adsorption/desorption behaviors on the surface and ultimately accelerating the catalytic kinetics. The formation of an alloy structure causes the ΔGH* of NiSb film (-0.46 eV) is smaller compared to the pure Ni (-1.12 eV) and pure Sb (-1.43 eV), and also the rate-determining step (RDS) of OER becomes “OOH* → O2” instead of “O* → OOH*”, so that the ∆GRDS is significantly reduced (from 2.1 eV for pure Ni to 1.7 eV for NiSb). Based on experimental validation, the NiSb exhibits low overpotentials of 298 mV and 473 mV at the current density of 100 mA.cm−2 toward the HER and OER in 0.5 M NaOH solution, benefiting from the collective plentiful active sites and the modulated electronic structure induced by alloying nickel and antimony. The obtained theoretical findings provide deep insights into the relationship between the catalytic properties of alloyed structures and intrinsic electronic configuration to design highly efficient catalysts for water splitting.

Modulating the electronic structure of NiFe hydroxide by Zr doping enables industrial-grade current densities for water oxidation

NiFe layered double hydroxide (LDH) is a non-noble benchmark catalyst for oxygen evolution reaction (OER). However, the mechanism of enhancing catalytic activities via incorporating foreign elements is still not resolved. Herein, we modulate the electronic structure of NiFe LDH by introducing high-valence Zr4+ to synergistically improve catalytic activity. NiFeZr LDH requires overpotential of only 182 mV at 10 mA cm−2 with Tafel slope of 38.6 mV dec−1. Impressively, it delivers 2000 mA cm−2 at only 314 mV and has robust durability over 750 h. Operational Raman analysis reveals that the electron transfer after incorporating Zr4+ inhibits oxidation of Ni2+ ions and restrains phase transition from active β-NiOOH to γ-NiOOH during OER process. Guided by density functional theory (DFT) computations, Zr4+ modulator promotes the rate-determining step from OH* to O* via optimizing the oxidation cycle at Fe active sites. This work provides a route for advancing electrocatalysts to meet industrial standards.

Realizing a Lattice Se Atom-Modified Co Hydroxide Catalyst via Electrochemical Reconstruction for Enhanced Oxygen Evolution Performance.

Realizing a highly efficient oxygen evolution reaction (OER) process is of great significance for hydrogen energy development. The main challenge still lies in fabricating superior electrocatalysts with favorable performance. Constructing electrocatalysts with ingenious lattice modifications is a considerable way for the rational design of highly active catalytic centers. Here, theoretical calculations predict that the lattice incorporation of Se atoms can effectively enhance the reaction activity of OER with a decreased energy barrier for the rate-determining step. To obtain the corresponding desired electrocatalyst, the optimized lattice Se-modified CoOOH, with the ideal OER performance of low overpotential and stability, was delicately designed and fabricated by the electrochemical activation of the Co0.85Se precatalyst. X-ray absorption spectroscopy (XAS) demonstrates that lattice incorporation is more likely to be generated in Co0.85Se compared to CoSe2 and CoO precatalysts, which promoted the subsequent OER process. This work clarified the correlation between the precatalyst and the lattice-modified final catalyst in connection with electrochemical reconstruction.

Understanding the Anion Effect of Basic Cobalt Salts for the Electrocatalytic Oxygen Evolution Reaction

Basic cobalt salts with distinct acidic anion Co(OH)x(A)y are efficient electrocatalysts toward the oxygen evolution reaction (OER). However, plenty of present studies are still in the try-and-wrong stage, while the underlying anion effect remains unclear. Herein, a series of Co(OH)x(A)y (A = F–, Cl–, and CO32–) are synthesized via a hydrothermal strategy, and the order of the OER activity is determined to be Co(OH)(CO3)0.5 > Co2(OH)3Cl > Co(OH)F > Co(OH)2. X-ray photoelectron spectroscopy and soft X-ray absorption spectroscopy studies reveal that these Co(OH)x(A)y materials undergo surface oxidation during the OER process, and the highly active Co(IV) content is the dominant factor in deciding the OER performance. Furthermore, quantitative analysis of anion concentrations in the electrolyte solution reveals that the anion leaching ability in Co(OH)x(A)y directly relates to the Co(IV) content and finally the OER catalytic activity, which is the essence of the anion effect and can be summarized as an “anion leaching─metal oxidation” model. Our work not only provides deep understanding of the anion effect of metal basic salt-based OER catalysts but also profound insights for the activation process of the OER pre-catalysts.

Fabrication of NiCo@Ni3S2/Nickel foam electrocatalyst with ultrathin NiCo layered double hydroxide film wrapping Ni3S2 nanoarrays for efficient oxygen evolution reaction

Developing efficient and durable electrocatalysts for faster anodic oxygen evolution reaction (OER) in water electrolysis is significant to hydrogen production. In this study, an electrocatalyst NiCo@Ni3S2/NF for OER was prepared using a two-step method. Ni3S2 nanoarray was initially grown on a nickel foam (NF) substrate, followed by the deposition of an ultrathin NiCo layered double hydroxides (LDH) film that wrapped around the surface of Ni3S2/NF to form a hill-shaped morphology. Characterization results of SEM, TEM, and XPS confirmed the presence of a heterogeneous interface with an enlarged contact area between NiCo LDH and Ni3S2 in this unique structure. This leads to more active species such as Ni3+ and Co3+, resulting in enhanced intrinsic catalytic activity. This hill-shaped topography also demonstrated to be conducive to the release of oxygen bubbles generated during OER process. The prepared electrocatalyst NiCo@Ni3S2/NF exhibits a rapid charge transfer rate and a Tafel slope as low as 63 mV·dec−1. It therefore demonstrates excellent OER performance with a low overpotential of 245 mV at current density of 10 mA cm−2, and long-term stability under both currents of 10 and 50 mA cm−2.

A Self-Templated Design Approach toward Multivariate Metal-Organic Frameworks for Enhanced Oxygen Evolution.

Multivariate metal-organic framework (MOF) is an ideal electrocatalytic material due to the synergistic effect of multiple metal active sites. In this study, a series of ternary M-NiMOF (M = Co, Cu) through a simple self-templated strategy that the Co/Cu MOF isomorphically grows in situ on the surface of NiMOF is designed. Owing to the electron rearrange of adjacent metals, the ternary CoCu-NiMOFs demonstrate the improved intrinsic electrocatalytic activity. At optimized conditions, the ternary Co3 Cu-Ni2 MOFs nanosheets give the excellent oxygen evolution reaction (OER) performance of current density of 10mA cm-2 at low overpotential of 288mV with a Tafel slope of 87mV dec-1 , which is superior to that of bimetallic nanosheet and ternary microflowers. The low free energy change of potential-determining step identifies that the OER process is favorable at Cu-Co concerted sites along with strong synergistic effect of Ni nodes. Partially oxidized metal sites also reduce the electron density, thus accelerating the OER catalytic rate. The self-templated strategy provides a universal tool to design multivariate MOF electrocatalysts for highly efficient energy transduction.

Cytomembrane-inspired engineering of oxygen transfer channel for modulating Ni/NiO heterostructure and boosting water oxidation

Development of low-cost and efficient non-precious metal electrocatalysts for oxygen evolution reaction (OER) is of predominant importance for promoting the large-scale application of water splitting. Herein, we use ZIF-8 as a sacrifice template, and successfully prepare the freestanding N-doped carbon nanofibers that decorated with Ni/NiO nanoparticles (denoted as xNi/NiO-NCNFs) via a scalable electrospinning-pyrolysis strategy. Inspired by the cytomembrane, we tune the dosage of ZIF-8 (x) to optimize the amount of micropores on the carbon layer that encapsulating the Ni species, which could act as oxygen transfer channels and enable suitable amount of oxygen to input to modulate the oxidation state of Ni. Moreover, the porous structure could facilitate the mass transfer of the reactants and contact with the active sites, as well as provide more channels for oxygen to release during the OER process. Benefiting from the synergistic effect of the Ni/NiO active sites, porous structure of carbon shell, and the doped N atoms, the 0.075Ni/NiO-NCNFs presents an ultralow overpotential of 210 mV to achieve a current density of 20 mA cm−2 in 0.1 M KOH solution and a low Tafel slope of 29.6 mV dec-1. This work provides a simple and cost-effective pathway to develop porous free-standing non-noble metal-based catalyst with high OER efficiency for potential sustainable electrochemical energy conversion.

Carbon-supported FeCoNiP/FeCoNi Mott-Schottky electrocatalyst for alkaline oxygen evolution reaction

Design of oxygen evolution reaction (OER) electrocatalysts with advanced composition and structure is essential for achieving highly efficient water splitting. Herein, we fabricated a Mott-Schottky electrocatalyst composed of trimetallic alloy and its phosphide (FeCoNiP/FeCoNi) on network-like carbon support. The catalyst was synthesized via a NaCl-template method followed by high-tempreture pyrolysis and low-tempreture phosphorization process. By optimization of the carbonization temperature, the electrocatalyst achieved a ultralow overpotential of 240 mV at 10 mA/cm2 and 302 mV at 100 mA/cm2 for OER, the most excellent OER performance in reported metallic phosphide catalysts and related heterojunction catalysts. The FeCoNiP/FeCoNi Mott-Schottky heterojunction enhanced the mass adsorption and electron transfer in the OER process, responsible for the excellent electrocatalytic activity. Meanwhile, the FeCoNiP on the surface endowed the catalyst good long-term durability in the alkaline electrolyte, even at 10 mA/cm2 for 40 h Our work provided a universal strategy for convenient and controllable synthesis of multi-component Mott-Schottky catalysts, the excellent electrocatalysis performance of which throw new light on the further practical applications.

2-Methylimidazole-induced synthesis of ZIF-67/CuO composite catalysts for enhanced oxygen evolution reaction activity

Developing high-efficient Cu-based catalysts for oxygen evolution reaction (OER) remains challenging under alkaline conditions. Herein, a series of ZIF-67/CuO composite catalysts on Cu foam (CF) were synthesized under controlling the molar ratio of Co2+ to 2-Methylimidazole. The formation of CuO nanobelts (NBTs) from CF and subsequent epitaxial growth of ZIF-67 particles facilitate the synergistic effect between components, which could enhance the charge/mass transfer in the electrocatalytic water oxidation process to achieve excellent OER activity. The optimal ZIF-67(R48)/CuO/CF composite sample obtained current densities of 50 and 200 mA cm–2 in 1.0 mol L–1 KOH with an overpotential of only 295 and 344 mV. Especially, the composite catalyst showed good stability on running 50 h at 20 mA cm–2 without obvious decay. The Cu-ZIF layer at the interface of ZIF-67 and CuO enabled fast electronic transfer between Cu and Co sites during the OER process, which is the key issue for excellent OER activity of the composite catalysts.

Efficient and stable electrocatalytic performances of nanostructured composite of CuO and Co2P in the full pH range towards hydrogen and oxygen evolution

It is highly desirable to explore non-noble metal catalysts with outstanding intrinsic activity and abundant active sites to ensure efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in the full pH range. In this article, we have prepared a nanoflower-shaped composite material of CuO and Co2P (CuO@Co2P) by extending nanowires on foam copper, which effectively increased the contact area while ensuring stability and conductivity. The synergistic effect between CuO and Co2P promotes the reactivity of HER and OER in the full pH range. For example, the CuO@Co2P/NF electrode requires only the overpotentials of 150 and 374 mV for HER to achieve 10 and 100 mA·cm−2 respectively, and 260 and 391 mV for OER current densities of 10 and 100 mA·cm−2, in 1 M KOH medium. And in a neutral electrolyte of 0.5 M Na2SO4, achieve the same current density values as 10 and 100 mA·cm−2, requires the overpotentials of 82 and 213 mV for HER, and 301 and 472 mV for OER, respectively. Furthermore, the HER overpotential of 206.3 mV is needed up to 100 mA·cm−2 in 0.5 M H2SO4 medium for CuO@Co2P/NF electrode. The composite CuO@Co2P has an excellent electrochemical stability, which shows only 7.12%, 4.02% and 5.3% of current density attenuation during HER tested in 0.5 M H2SO4, 0.5 M Na2SO4 and 1 M KOH, respectively, and the rates of change in the OER process in 0.5 M Na2SO4 and 1 M KOH media are 4.79% and 3.46%. This work expands the efficient application of electrocatalysts in the full pH range and avoids the release of toxic gases during phosphating, which is of great significance for the development of transition metal phosphating composite electrocatalysts.

Polarization Manipulation of NiO Nanosheets Engineered with Fe/Pt Single Atoms for High-Performance Electrocatalytic Overall Alkaline Seawater Splitting

Regulating the metal–support interaction is recognized as an effective approach to modulating the electronic structure of single-atom catalysts. Here, we put forward a strategy to modulate the anchored metallic single atoms by manipulating the surface polarization of the support, which is demonstrated to be effective in designing alkaline seawater electrocatalysts. Specifically, we introduce Mn doping in weak-polarized NiO nanosheets to modulate its surface polarization and thereby regulate the electronic metal–support interaction between anchored Pt/Fe single atoms and NiO support. The optimized Pt1/Mn_NiO||Fe1/Mn_NiO electrode pair exhibits superior overall alkaline seawater-splitting performance, achieving an impressive low cell voltage of 1.44 V at a current density of 10 mA cm–2. The experimental characterizations and theoretical calculations highlight the significance of Mn doping in the surface polarization regulation of NiO. Moreover, the charge redistributions and the changes in coordination structure induced by Mn doping in Pt1/Mn_NiO and Fe1/Mn_NiO account for the decreased Gibbs free energy for the rate-determining steps in the HER and oxygen evolution reaction processes. This work demonstrates an effective method to design efficient alkaline seawater electrocatalysts by modulating electronic metal–support interaction over surface polarization regulation.