Spherical Co3S4 grown directly on Ni–Fe sulfides as a porous nanoplate array on FeNi3 foam: a highly efficient and durable bifunctional catalyst for overall water splitting

Abstract

Designing high-performance, low-cost non-precious metal bifunctional electrocatalysts for either the hydrogen evolution reaction (HER) or the oxygen evolution reaction (OER) is the key to achieving large-scale hydrogen production from water. Here, we design a porous nanosheet array catalyst of spherical Co₃S₄ and Ni–Fe sulfide nanosheets grown vertically on FeNi₃ foam (NiFeCoS_x@FeNi₃) with excellent catalytic activity and stability in alkaline solutions. In 1.0 M KOH solution, the current densities of the HER and OER can reach 10 mA cm⁻² with minimum overpotentials of 88 mV and 210 mV, respectively. In 1.0 M KOH and 0.33 M urea solutions, NiFeCoS_x@FeNi₃ needs only 1.42 V to provide a current density of 10 mA cm⁻² for the urea oxidation reaction (UOR). The significantly improved catalytic activity should be attributed to the synergistic interaction among the three elements of Ni, Fe and Co as well as the hierarchical porous nanosheet array structure. This work demonstrates that a novel and efficient bifunctional trimetallic catalyst can be rationally designed by controlling the composition and ratio of the elements and the structure.