Type-II InSe/ g-C3N4 Heterostructure as a High-Efficiency Oxygen Evolution Reaction Catalyst for Photoelectrochemical Water Splitting.

We propose a conceptual design of InSe/ g-C3N4 van der Waals heterostructure to achieve highly efficient and spontaneous water splitting. InSe/ g-C3N4 possesses a direct band gap of 2.04 eV with type-II band alignment, which is beneficial to the separation of electrons and holes and exhibits proper valence and conduction-band positions for the redox reactions of H2O. In addition, the adsorption of multiple water molecules and the changes of free energy on InSe/ g-C3N4 have been calculated to understand the oxygen evolution reaction (OER) process of water splitting. The free energies of reaction on three sides are all downhill, and the values of Δ G reduce to about -0.406 eV, indicating that the OER of water splitting is a thermodynamically permissible reaction without the aid of any other substance. Therefore, the water-splitting reaction could be thermodynamically continued using InSe/ g-C3N4 as a photocatalyst, which indicates that InSe/ g-C3N4 is an excellent candidate for photocatalyst or photoelectronic applications.