Fe and Cu dual-doped Ni3S4 nanoarrays with less low-valence Ni species for boosting water oxidation reaction

Abstract

Transition metal materials with high efficiency and durable electrocatalytic water splitting activity have attracted widespread attention among scientists. In this work, two cation co-doped Ni₃S₄ nanoarrays grown on a Ni foam support were firstly synthesized through a typical two step hydrothermal process. Cu and Fe co-doping can regulate the internal electron configuration of the material, thus reducing the activation energy of the active species. Moreover, density functional theory calculations demonstrate that a low Ni²⁺ amount improves the adsorption energy of H₂O, which facilitates the formation and reaction of intermediate species in the water splitting process. The experimental results indicate that the Cu and Fe co-doped Ni₃S₄ material has superior electrochemical activity for water oxidation reaction to pure Ni₃S₄, Fe doped Ni₃S₄ and Cu doped Ni₃S₄. The Fe–Cu–Ni₃S₄ material displays a significantly enhanced electrocatalytic performance with low overpotentials of 230 mV at 50 mA cm⁻² and 260 mV at 100 mA cm⁻² for the oxygen evolution reaction under alkaline conditions. It's worth noting that when Fe–Cu–Ni₃S₄ was used as the anode and cathode, a small cell voltage of 1.59 V at 10 mA cm⁻² was obtained to achieve stable overall water splitting. Our work will afford a novel view and guidance for the preparation and application of efficient and environmentally friendly water splitting catalysts.