Ultrahigh electrocatalytic oxygen evolution by iron-nickel sulfide nanosheets/reduced graphene oxide nanohybrids with an optimized autoxidation process

Iron-nickel-based electrocatalysts are a group of noble-metal-free and high-performance candidate for oxygen evolution reaction (OER), and autoxidation always occurs in their OER process. Autoxidation is a double-edged sword: it could in-situ generate high-catalytic activity sites to accelerate OER, but it also results in the attenuation of conductivity and the dissolution of active components. In this work, we propose a new strategy to relieve the negative impacts of autoxidation on OER through designing three-dimensional (3D) iron-nickel sulfide nanosheets/reduced graphene oxide (FeNiS₂ NS/rGO) nanohybrids via a one-pot colloidal method, which enabled the well dispersion and strong coupling of FeNiS₂ NS on the rGO. Such an interconnected 3D architecture could facilitate excellent electron transport, provide large amounts of active sites and prevent the dissolution of active components. The FeNiS₂ NS/rGO delivered extremely low overpotentials of 270 mV and 200 mV to reach a current density of 10 mA cm⁻², and rapid kinetics with Tafe slope of 38 mV dec⁻¹ and 40 mV dec⁻¹ for OER in 0.1 and 1.0 M KOH, respectively. Moreover, they could retain a great stability without activity loss over long-term continuous electrolysis and long-ageing time under air conditions. This work provides an efficient approach to resolve the autoxidation problem of FeNiS₂ NS in the OER process and develops a promising earth-abundant OER electrocatalyst towards practical applications.