Accelerating water dissociation at carbon supported nanoscale Ni/NiO heterojunction electrocatalysts for high-efficiency alkaline hydrogen evolution

The synergistic catalysis of heterojunction electrocatalysts for the multi-step process in hydrogen evolution reaction(HER)is a promising approach to enhance the kinetics of alkaline HER.Herein,we proposed a strategy to form nanoscale Ni/NiO heterojunction porous graphitic carbon composites(Ni/NiO-PGC)by reduction-pyrolysis of the preformed Ni-metal-organic framework(MOF)under H2/N2 atmosphere.Benefiting from low electron transfer resistance,increased number of active sites,and unique hierarchical micro-mesoporous structure,the optimized Ni/NiO-PGC_(10-1-400)exhibited excellent electrocatalytic performance and robust stability for alkaline HER(η10=30 mV,65 h).Density functional theory(DFT)studies revealed that the redistribution of electrons at the Ni/NiO interface enables the NiO phase to easily initiate the dissociation of alkaline H_(2)O,and shifts down the d-band center of Ni and optimizes the H*adsorption-desorption process of Ni,thereby leading to extremely high HER activity.This work contributes to a further understanding of the synergistic promotion of the multi-step HER processes by heterojunction electrocatalysts.