Deciphering the structure evolution and active origin for electrochemical oxygen evolution over Ni3S2

Transition metal chalcogenides (TMCs) have been reported as efficient pre-catalysts for alkaline oxygen evolution reaction (OER). However, inadequate cognition about the electrochemical activation-induced structure evolution and effect of the residual anions leads to insufficient theoretical guidance for the rational design of highly effective catalyst. Herein, Ni3S2 nanoflakes vertically grown on Ni foam (Ni3S2/NF) are successfully achieved to behave as the pre-catalyst. Systematic experimental investigation and theoretical calculation endorse that stepwise S leaching combined with OH− adsorption is conducive to boosting the structure evolution of Ni3S2/NF into NiOOH/Ni3S2/NF. In addition, the residual SO42− anchored on the surface of reconstructed catalyst could enhance the adsorption of reactive intermediates and decrease the stepwise energy barrier for OER. As a result, the reconstructed NiOOH/Ni3S2/NF exhibits superior OER performance with an overpotential of 255.4 mV to deliver a current density of 10 mA cm2. In addition, remarkable electrocatalytic performance for overall water splitting is achieved with NiOOH/Ni3S2/NF and Ni3S2/NF as anode and cathode, respectively, featured for 1.57 V (vs. RHE) to powering overall water electrolysis with a current density of 10 mA cm2. This work supplies valuable insights for fundamental understanding and rational construction of efficient nickel-based OER catalyst.