C2N/WS2 van der Waals type-II heterostructure as a promising water splitting photocatalyst

Photocatalytic water splitting has long been considered as a source of pollution-free clean energy and finding an efficient photocatalyst for this reaction has remained a major challenge. Here, we study C2N/WS2 van der Waals heterostructure as a possible photocatalyst for water splitting. Using first principles calculations, we find that band edges of the heterostructure are found to satisfy both water oxidation and reduction energy levels, ensuring the occurrence of these two reactions. Additionally, it is found to be a type-II heterostructure, that enables the separation of electrons and holes in two different layers upon light irradiation and thereby facilitates water oxidation on WS2 layer and water reduction on C2N layer. The charge transfer occurs from WS2 to C2N monolayer, which serves dual purpose of separating photoinduced charge carriers and extending their lifetimes. The heterostructure also shows high charge carrier mobilities, indicating their efficient utilization in reduction and oxidation reactions before recombination. Most importantly, light absorption in visible range for the heterostructure is significantly enhanced compared to the constituent monolayers, rendering it to be a suitable photocatalyst for water splitting. Thermodynamic analysis for redox reactions suggest facile hydrogen generation on the heterostructure. Our study explains the underlying mechanism of the enhanced photocatalytic activity of C2N/WS2 heterostructure, which could further lead to designing of wider range of 2D heterostructured photocatalysts.