Boosting electrocatalytic water oxidation by vanadium–iron–nickel trimetal hydroxide catalysts through interphase ionic migration method

Abstract

Non-noble metals are expected to displace the position of the traditional noble metals as catalysts in accelerating sluggish kinetics during water oxidation within hydrogen energy utilization. Among them, nickel–iron-based catalysts have been found to be particularly worth developing for their superior catalytic performance in alkaline electrolytes and their high geological abundance. In this article, we synthetized an OER electrocatalyst with an abundance of oxygen vacancies, vanadium–iron–nickel trimetallic hydroxide nanosheets loaded on a VO(OH)₂ substrate. The obtained electrocatalyst VFeNi/VO(OH)₂-2 exhibits a superb low OER overpotential of 251 mV for 10 mA cm⁻² current density, and maintains superior stability for over 5 days. Compared to commercial IrO₂ and the majority of currently published non-noble metal catalysts, this novel electrocatalyst performs much better. Interphase ionic migration occurred between VO(OH)₂ nanorods and VFeNi nanosheets. Additionally, XPS and EPR analysis demonstrated that vanadium ion migration introduced abundant oxygen vacancies (O_v), which help to improve the electrical coordination and conductivity. Density functional theory (DFT) calculations provide further evidence that regulation of the density of electronic states and the adsorption energy of oxygen species by vanadium migration helps to depress the energy barrier of water-splitting.