Dynamic Fe3+ equilibrium and Ce-Doping Electronic Synergy in Ni3S2/NiS Heterostructures for Enhanced Alkaline Oxygen Evolution

Abstract

The incorporation of iron species in transition metal sulfide systems can significantly enhance the oxygen evolution reaction (OER) catalytic activity. 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 successfully constructed an Fe/Ce doped Ni3S2/NiS heterostructure (denoted as FeOOH, Ce-Ni3S2/NiS) on nickel foam substrates through a combined hydrothermal sulfidation and electrochemical activation approach. By establishing a dynamic dissolution-adsorption equilibrium between Fe3+ in the electrolyte and the surface FeOOH layer, it effectively mitigated the loss of active sites. Simultaneously, the constructed Fe-Ce dual-active sites further stabilized the catalytic interface through synergistic effects. OER performance tests demonstrated that the catalyst required 266 mV overpotential to achieve 100 mA cm-2, with significantly improved Tafel slope (27.35 mV dec-1) and charge transfer resistance (1.161 Ω) compared to control samples. Remarkably, the catalyst maintained stable operation for 100 hours at an ultrahigh current density of 2.0 A cm-2. In addition, the anion-exchange membrane (AEM) electrolyzer (FeOOH, Ce-Ni3S2/NiS//Pt) was operated 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.