High hydrogen production in the InSe/MoSi 2 N 4 van der Waals heterostructure for overall water splitting.

Very recently, the septuple-atomic-layer MoSi 2 N 4 has been successfully synthesized by a chemical vapor deposition method. However, pristine MoSi 2 N 4 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 MoSi 2 N 4 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/MoSi 2 N 4 heterostructure have been systematically investigated by density functional theory for the first time. The results demonstrate that 2D InSe/MoSi 2 N 4 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/MoSi 2 N 4 has high electron mobility (10 4 cm 2 V -1 s -1 ) and shows a noticeable optical absorption coefficient (10 5 cm -1 ) in the visible-light region of the solar spectrum. These brilliant properties declare that 2D InSe/MoSi 2 N 4 is a potential photocatalyst for overall water splitting.