High hydrogen production in the InSe/MoSi₂N₄ van der Waals heterostructure for overall water splitting

Very recently, the septuple-atomic-layer MoSi₂N₄ has been successfully synthesized by a chemical vapor deposition method. However, pristine MoSi₂N₄ exhibits some shortcomings, including poor visible-light harvesting capability and a low separation rate of photo-excited electron-hole pairs, when it is applied in water splitting to produce hydrogen. Fortunately, we find that MoSi₂N₄ can be considered as a good co-catalyst to be stacked with InSe forming an efficient heterostructure photocatalyst. Here, the electronic and photocatalytic properties of the two-dimensional (2D) InSe/MoSi₂N₄ heterostructure have been systematically investigated by density functional theory for the first time. The results demonstrate that 2D InSe/MoSi₂N₄ has a type-II band alignment with a favourable direct bandgap of 1.61 eV and exhibits suitable band edge positions for overall water splitting. Particularly, 2D InSe/MoSi₂N₄ has high electron mobility (10⁴ cm² V^-1 s^-1) and shows a noticeable optical absorption coefficient (10⁵ cm^-1) in the visible-light region of the solar spectrum. These brilliant properties declare that 2D InSe/MoSi₂N₄ is a potential photocatalyst for overall water splitting.