Promising Photocatalysts for Water Splitting in BeN2 and MgN2 Monolayers

Currently, identifying suitable photocatalysts, especially in two-dimensional materials, for photocatalytic water splitting is still challenging. Here, we report the identification of BeN2 and MgN2 monolayers as efficient photocatalysts for water spitting. Our phonon spectra and ab initio molecular dynamics simulations provide eloquent examinations for the dynamical and thermal stabilities of these two monolayers. We find that BeN2 monolayer exhibits a direct band gap of 2.26 eV, whereas MgN2 monolayer shows an indirect band gap of 2.33 eV. The carrier mobility for BeN2 monolayer is up to 105 and 104 cm2 V–1 s–1 for MgN2 monolayer. More importantly, the BeN2 monolayer has appropriate band edge alignment with respect to the water reduction and oxidation levels in water splitting, whereas MgN2 monolayer satisfies the reduction levels in water splitting only. These results imply that BeN2 monolayer can be a potential photocatalyst for water splitting, whereas MgN2 monolayer can be a potential hydrogen production material.