Heterostructured nickel, iron sulfide@nitrogen, sulfur co-doped carbon hybrid with efficient interfacial charge redistribution as bifunctional catalyst for water electrolysis

Abstract Efficient and bifunctional catalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is crucial for achieving of easily-operable water electrolysis. Herein, Ni,Fe sulfides embedded N,S co-doped carbon hybrids (NiFeS@NSCs) with tunable Ni:Fe ratios were devised through pyrolysis of methionine chelated Ni, Fe precursors. In this type of heterojunction hybrids, the spontaneous diffusion of electrons from embedded sulfides to NSC shell increases the reducibility of NSC and the oxidizability of sulfides, which are therefore capable of catalyzing OER and HER simultaneously. The typical Ni2FeS@NSC hybrid with Ni:Fe molar ratio of 2:1 offered high electrocatalytic ability for alkali OER (overpotential of 247 mV at 10 mA cm-2), which is significantly superior to that of individual sulfide. In addition, good HER efficiency was concurrently ensured by Ni2FeS@NSC. The symmetric water electrolyzer based on Ni2FeS@NSC required an input voltage of 1.77 V to arouse an electrolysis current density of 10 mA cm-2. This work offers a feasible approach to enhance the OER, HER bifunctional catalytic performances via interfacial electrons diffusion within heterostructured hybrid.