Dynamic Fe3+ equilibrium and Ce-doping electronic synergy in Ni3S2/NiS heterostructures for enhanced alkaline oxygen evolution

Abstract

The introduction of iron significantly enhances the catalytic activity of a catalytic system for the oxygen evolution reaction (OER). However, the high dissolution tendency of iron components may lead to irreversible loss of active sites, thereby compromising the long-term stability of the catalytic system. Herein, we constructed a heterostructure of FeOOH decorated Ce-Ni₃S₂/NiS (FeOOH,Ce-Ni₃S₂/NiS) on a nickel foam substrate through a combined approach of hydrothermal sulfidation and electrochemical activation. By establishing a dynamic dissolution–adsorption equilibrium between Fe³⁺ in the electrolyte and the surface FeOOH layer, the loss of active sites was effectively mitigated. Simultaneously, the Fe(3d)–Ce(4f) orbital coupling effectively modulates the electronic structure of metal active centers, constructing a highly stable Ni₃S₂/NiS electrocatalytic system. OER performance tests show that the catalyst delivers 266 mV overpotential to achieve 100 mA cm⁻², while demonstrating exceptional durability by maintaining stability for 100 h at an ultrahigh current density of 2.0 A cm⁻². In addition, an anion-exchange membrane (AEM) electrolyzer (FeOOH,Ce-Ni₃S₂/NiS//Pt) maintains operation continuously for 100 hours at 1000 mA cm⁻². This study proposes an electrolyte-mediated dynamic interface regulation strategy, providing new design principles for developing industrial water electrolysis catalysts with both high activity and exceptional stability.