Nitrogen vacancies in monolayer WSi2N4 for hydrogen evolution reaction: A first-principles study

The recent synthesis of two-dimensional layered WSi2N4 has attracted considerable attention owing to its potential applications in diverse fields. In this study, we use first-principles density functional theory calculations to investigate the catalytic performance of WSi2N4 monolayers with nitrogen (N) vacancies in the hydrogen evolution reaction. The calculated Gibbs free energies of the WSi2N4 monolayers are –0.09 eV and –0.10 eV at the vacancy concentrations of 5.6 % and 12.5 %, respectively, which are close to the zero optimal value. The results indicate that the defective WSi2N4 monolayers can exhibit remarkably high catalytic activity comparable to that of platinum catalysts in the hydrogen evolution reaction. In addition, our electronic structure calculations demonstrate the emergence of spin-polarized states near the Fermi level upon introducing N vacancies, which can be attributed to isotropic Zeeman-type spin-splitting.