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.