Atomic precision tailoring of two-dimensional MoSi2N4 as electrocatalyst for hydrogen evolution reaction

Septuple-atomic-layer MoSi2N4 has emerged as a promising and non-precious energy conversion material due to its stable and unique crystal structures. Unfortunately, the MoSi2N4 monolayer shows an inert catalytic active feature due to the large positive Gibbs free energy (ΔGH). To overcome the main drawback, an effective alternative is to design MoSi2N4 with different modifications. The results show that the electronic properties can be significantly tailored with the atomic vacancies, substitutions and biaxial strains with the band gap reduced to near zero eV when B and O dopants are incorporated into MoSi2N4 monolayer. Moreover, the continuous decrease of band gap can also be obtained by applying the tensile strains on MoSi2N4 monolayer. The ELF and charge transfer analyses show that the modifications induce various cation–anion bond features for the MoSi2N4. The changes of bond features greatly enhance the hydrogen adsorption on the MoSi2N4, rendering a suitable ΔGH (near 0 eV) for HER. The obvious enhancement is owing to the H-1 s orbital splitting into two parts located below and above Fermi energy due to the strong hybridization between the hydrogen atom and catalyst. These results suggest the great potential of such modified MoSi2N4 monolayer as highly efficient HER electrocatalyst for practical applications.