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, Ni 3 S 2 nanoflakes vertically grown on Ni foam (Ni 3 S 2 /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 Ni 3 S 2 /NF into NiOOH/Ni 3 S 2 /NF. In addition, the residual SO 4 2− 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/Ni 3 S 2 /NF exhibits superior OER performance with an overpotential of 255.4 mV to deliver a current density of 10 mA cm 2 . In addition, remarkable electrocatalytic performance for overall water splitting is achieved with NiOOH/Ni 3 S 2 /NF and Ni 3 S 2 /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 cm 2 . This work supplies valuable insights for fundamental understanding and rational construction of efficient nickel-based OER catalyst.