Monolayer MoSi2N4-x as promising electrocatalyst for hydrogen evolution reaction: A DFT prediction

lDefective MoSi2N4 with surface nitrogen vacancy (NV) is predicted to be a promising HER electrocatalyst by DFT calculations.lSurface NV can be introduced in monolayer MoSi2N4 under the N-poor condition.lThe HER activity of defective MoSi2N4 is surface NV concentration dependent.lThe relationship between HER activity and the center of Si-3p band is revealed.