  Single-atom catalysts are considered as a promising method for efficient
energy conversion, owing to their advantages of high atom utilization and low
catalyst cost. However, finding a stable two-dimensional structure and high
hydrogen evolution reaction (HER) performance is a current research hotspot.
Herein, based on the first-principles calculations, we identify the HER
properties of six catalysts (TM@MoSi2N4, TM = Sc, Ti, V, Fe, Co, and Ni)
comprising transition metal atoms anchored on MoSi2N4 monolayer. The results
show that the spin-polarized states appear around the Fermi level after
anchoring TM atoms. Therefore, the energy level of the first available
unoccupied state for accommodating hydrogen drops, regulating the bonding
strength of hydrogen. Thus, the single transition metal atom activates the
active site of the MoSi2N4 inert base plane, becoming a quite suitable site for
the HER. Based on {\Delta}GH*, the exchange current density and volcano diagram
of the corresponding catalytic system were also calculated. Among them,
V@MoSi2N4 ({\Delta}GH* = -0.07 eV) and Ni@MoSi2N4 ({\Delta}GH* = 0.06 eV)
systems show efficient the HER property. Our study confirms that the transition
metal atom anchoring is an effective means to improve the performance of
electrocatalysis, and TM@MoSi2N4 has practical application potential as a high
efficiency HER electrocatalyst.
