First-principles study of direct Z-scheme GaS/WTe2 van der Waals heterostructure as photocatalyst for water splitting

The effective separation of charge carriers and the redox capacity for water splitting are two crucial factors that influence photocatalysis. Here, we studied the photocatalytic properties of GaS/WTe2 van der Waals heterostructure (vdWH) using first-principle calculations. The results show that this heterostructure acts as a direct Zscheme with GaS as the water oxidation photocatalyst and WTe2 as the water reduction photocatalyst. Photogenerated charge carriers are efficiently separated, with electrons in GaS combining with holes in WTe2, while other charge carriers with high redox ability remain in the respective materials for water splitting. More importantly, the heterostructure exhibits excellent performance in all acid and alkali solutions (pH 0-14) and has strong light absorption in the ultraviolet (UV) and visible region. The power conversion efficiency(PCE) reaches 19.73%. This work reveals that GaS/WTe2 heterostructure is a highly promising material for photocatalytic water splitting.