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

Abstract

l Defective MoSi 2 N 4 with surface nitrogen vacancy (NV) is predicted to be a promising HER electrocatalyst by DFT calculations. l Surface NV can be introduced in monolayer MoSi 2 N 4 under the N-poor condition. l The HER activity of defective MoSi 2 N 4 is surface NV concentration dependent. l The relationship between HER activity and the center of Si-3p band is revealed. The density functional theory (DFT) calculations have been performed to investigate the catalytic properties of monolayer MoSi 2 N 4 for hydrogen evolution reaction (HER). The DFT results show that similar to the majority of other two-dimensional (2D) materials, the pristine MoSi 2 N 4 is inert for HER due to its weak affinity toward hydrogen, while monolayer MoSi 2 N 4- x ( x = 0‒0.25) exhibits the highly desirable HER catalytic activities by introducing surface nitrogen vacancy (NV). The predicted HER overpotential (0‒60 mV) of monolayer MoSi 2 N 4- x is lower than that (90 mV) of noble metal Pt, when the concentration of surface NV is lower than 5.6%. Electronic structure calculations show that the spin-polarized states appear around the Fermi level after introducing surface NV, thus making the surface NV on 2D MoSi 2 N 4 a quite suitable site for HER. Moreover, the HER activity of MoSi 2 N 4- x is highly dependent on the surface NV concentration, which can be further related to the center of Si-3p band. Our results demonstrate that the newly discovered 2D MoSi 2 N 4 can be served as a promising electrocatalyst for HER via appropriate defect engineering.