Charge transport regulation in Cu1.94S-ZnS-Co9S8 heterostructures via band alignment engineering for photocatalytic hydrogen evolution

Abstract

A facile sequential cation exchange reaction approach to synthesise two types of ternary sulphide NHs with comparable bulk composition, crystal structure, particle size and interfacial quality, but inverted component sequences of Cu_1.94S-ZnS-Co₉S₈ (CZC) and Cu_1.94S-Co₉S₈-ZnS (CCZ) was reported. Femtosecond transient absorption spectroscopy revealed that the ZnS/Co₉S₈ interface enables efficient charge transfer (τ₃ = 46.49 ps) in CZC, whereas the same interface hinders efficient charge migration and leads to severe non-radiative recombination in CCZ. This difference in charge transport behaviour results in a higher hydrogen evolution rate for CZC. Furthermore, extending this strategy to larger-sized rod-shaped CZC NHs achieves a high hydrogen evolution rate of 1047.2 μmol g^-1 h^-1 with improved structural stability.