Cobalt and nitrogen co-doped Ni3S2 nanoflowers on nickel foam as high-efficiency electrocatalysts for overall water splitting in alkaline media

Abstract

The development of high-performance and cost-effective bifunctional water splitting catalysts has enormous significance in the hydrogen production industry from water electrolysis. Herein, an in situ Co and N co-doping method was developed to improve the electrocatalytic performance of Ni₃S₂ catalysts. The Co–N-Ni₃S₂/NF is successfully synthesized for the first time by a one-step hydrothermal method, wherein nickel foam, thioacetamide and Co(NO₃)₂·6H₂O are used as the nickel source, sulfur source, nitrogen source and cobalt source. Co–N-Ni₃S₂/NF exhibits excellent oxygen evolution reaction activity (an overpotential of 285 mV@50 mA cm⁻²) and hydrogen evolution reaction activity (an overpotential of 215 mV@10 mA cm⁻²) in 1 M KOH solution. The electrolytic cell displayed a low cell voltage of 1.50 V when the Co–N-Ni₃S₂/NF material was used as the bifunctional water splitting electrocatalyst, which is one of the best catalysts reported so far. Density functional theory calculations show that Co–N-Ni₃S₂/NF exhibits stronger water adsorption energy than those of N-Ni₃S₂/NF, Co-Ni₃S₂/NF and Ni₃S₂/NF. It is proved that the doping of Co and N can effectively regulate the electron cloud density of Ni, thus enhancing the electrochemical activity of Co–N-Ni₃S₂/NF.