Cobalt and nitrogen co-doped Ni<sub>3</sub>S<sub>2</sub> nanoflowers on nickel foam as high-efficiency electrocatalysts for overall water splitting in alkaline media
Xiaoqiang Du, Guangyu Ma, Xiaoshuang Zhang
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.