Construction of Heterostructured NiS/NiSe2 and their application in electrocatalytic water splitting

Development of non-precious metal electrocatalyst that can efficiently catalyze the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) simultaneously, is a great challenge. Herein, density functional theory (DFT) calculations are first conducted to explore the beneficial effect of NiSe2/NiS heterostructure on OER. Based on this, a series of nickel selenosulfides constructed by different amounts of NiS and NiSe2 are synthesized. Results indicate that Ni4–Se2–S2 with the NiS to NiSe2 ratio of 5.82/2.47 displays outstanding electrocatalytic activity for OER/HER, with overpotentials of 228 mV and 155 mV at 10 mA cm−2, respectively. Moreover, a two-electrode electrolyzer using Ni4–Se2–S2 as the anode and cathode exhibits a lower voltage than RuO2||Pt/C. Moderate ratio of NiS to NiSe2 achieves a balance between conductivity and surface area, which endows Ni4–Se2–S2 the best catalytic performances. Our results pave a way for the optimization of heterostructured catalysts.