Influence of the S:Ni ratio in raw materials on the NixSy electrocatalysts

Nickel sulfides have been considered to be among the most effective oxygen evolution reaction (OER) electrocatalysts . Until now, there are many different nickel sulfides, such as Ni 3 S 2 , NiS, Ni 3 S 4 , NiS 2 , etc. In this paper, we set out to explore the influence of the S:Ni ratio in raw materials on the different nickel sulfides. With the characterizations of XRD , XPS , SEM, TEM and BET, the relevance between the molar ratio of S:Ni in raw materials and stoichiometric ratio, microscopic structure and OER performance are discussed. According to the results of the experiments, the Ni 3 S 4 derived from the 3:1 M ratio of S:Ni in raw material exhibits the smallest overpotential (245 and 314 mV to achieve 10 and 20 mA/cm 2 ) and Tafel slope (81.5 mV/dec). Meanwhile, theoretical calculation of ΔG(H 2 O*) indicate that the adsorption energy in Ni 3 S 4 is much closer to the IrO 2 than other nickel sulfides, which are in good agreement with the OER performance of electrochemical measurements.