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

The density functional theory (DFT) calculations have been performed to investigate the catalytic properties of monolayer MoSi2N4 for hydrogen evolution reaction (HER). The DFT results show that similar to the majority of other two-dimensional (2D) materials, the pristine MoSi2N4 is inert for HER due to its weak affinity toward hydrogen, while monolayer MoSi2N4-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 MoSi2N4-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 MoSi2N4 a quite suitable site for HER. Moreover, the HER activity of MoSi2N4-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 MoSi2N4 can be served as a promising electrocatalyst for HER via appropriate defect engineering.