Electrochemical water splitting proves critical to sustainable and clean hydrogen fuel production.However,the anodic water oxidation reaction—the major half-reaction in water splitting—has turned into a bottleneck due to the high energy barrier of the complex and sluggish four-electron transfer process.Nickel-iron layered double hydroxides(NiFe-LDHs)are regarded as promising non-noble metal electrocatalysts for oxygen evolution reaction(OER)catalysis in alkaline conditions.However,the electrocatalytic activity of NiFe-LDH requires improvement because of poor conductivity,a small number of exposed active sites,and weak adsorption of intermediates.As such,tremendous effort has been made to enhance the activity of NiFe-LDH,including introducing defects,doping,exfoliation to obtain single-layer structures,and constructing arrayed structures.In this study,researchers controllably doped NiFe-LDH with tungsten using a simple one-step alcohothermal method to afford nickel-iron-tungsten layered double hydroxides(NiFeW-LDHs).X-ray powder diffraction analysis was used to investigate the structure of NiFeW-LDH.The analysis revealed the presence of the primary diffraction peak corresponding to the perfectly hexagonal-phased NiFe-LDH,with no additional diffraction peaks observed,thereby ruling out the formation of tungsten-based nanoparticles.Furthermore,scanning electron microscopy(SEM)showed that the NiFeW-LDH nanosheets were approximately 500 nm in size and had a flower-like structure that consisted of interconnected nanosheets with smooth surfaces.Additionally,it was observed that NiFeW-LDH had a uniform distribution of Ni,Fe,and W throughout the nanosheets.X-ray photoelectron spectra(XPS)revealed the surface electronic structure of the NiFeW-LDH catalyst.It was determined that the oxidation state of W in NiFeW-LDH was +6 and that the XPS signal of Fe in NiFeW-LDH shifted to a higher oxidation state compared to NiFe-LDH.These results suggest electron redistribution between Fe and W.Simultaneously,the peak area of surface-adsorbed OH increased significantly after W doping,suggesting enhanced OH adsorption on the surface of NiFeW-LDH.Furthermore,density functional theory(DFT)calculations indicated that W(VI)facilitates the adsorption of H2O and O*-intermediates and enhances the activity of Fe sites,which aligns with experimental results.The novel NiFeW-LDH catalyst displayed a low overpotential of 199 and 237 mV at 10 and 100 mA∙cm-2 in 1 mol∙L-1 KOH,outperforming most NiFe-based colloid catalysts.Furthermore,experimental characterizations and DFT+U calculations suggest that W doping plays an important role through strong electronic interactions with Fe and facilitating the adsorption of important O-containing intermediates.
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