In Situ Electrochemically Formed Ag/NiOOH/Ni(3)S(2 )Heterostructure Electrocatalysts with Exceptional Performance toward Oxygen Evolution Reaction

Developing ultrahigh-activity and ultralong-durabil-ity electrocatalysts for oxygen evolution reaction (OER) in alkalinemedia is of great significance for large-scale alkaline water splitting.Herein, we report a self-supported heterostructure electrocatalystcomposed of Ni3S2nanosheet arrays decorated with Ag nano-particles grown on nickel foam (Ag/Ni3S2/NF). Specifically, theinsightful studies reveal that the amorphous NiOOH in situ formedon the surface of heterostructure electrocatalyst during OER(NiOOH@Ag/Ni3S2/NF) is regarded as the real active species.This self-constructed electrode only needs low overpotentials of183, 195, and 263 mV at the current density of 10, 20, and 100 mAcm-2, respectively, as well as a low Tafel slope of 37 mV dec-1in 1M KOH, and is maintained for 500 h almost without anydegradation at a high current density of 100 mA cm-2. Density functional theory (DFT) calculations reveal that the synergisticeffects among multiple components can effectively boost the intrinsic OER activity via increasing conductivity and optimizingbinding energy of oxygen-contained intermediates, and the enhanced Ni-O bonding accounts for the superior durability. This workprovides deep insight into the key role of Ag on boosting both the catalytic activity and the stability of nickel sulfides toward OER.