Monolayer MoSi_(2)_N(4-x) 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 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.