Construction of CoS/Cd0.5Zn0.5S ohmic heterojunctions for improving photocatalytic hydrogen production activity

Abstract

CoS/Cd_0.5Zn_0.5S ohmic heterojunctions were successfully constructed by a two-step solvothermal method. The CoS/Cd_0.5Zn_0.5S heterojunctions were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (UV-vis) and ultraviolet photoelectron spectroscopy (UPS). The introduction of CoS can effectively improve the photocatalytic hydrogen evolution activity of Cd_0.5Zn_0.5S, and its content has an impact on the activity of the CoS/Cd_0.5Zn_0.5S heterojunction. The hydrogen evolution rate of the 30%-CoS/Cd_0.5Zn_0.5S nanocomposite reached 6916.7 μmol g⁻¹ h⁻¹ in 3 vol% lactic acid aqueous solution with an optimal quantum efficiency of 9.32%, which is 5.1 times that of pure Cd_0.5Zn_0.5S. Moreover, the 30%-CoS/Cd_0.5Zn_0.5S sample shows good photocatalytic hydrogen production stability. Mechanistic studies suggest that CoS/Cd_0.5Zn_0.5S with an ohmic heterojunction can effectively transfer and separate the photogenerated electrons and holes, thereby improving the photocatalytic hydrogen production. This work could offer a facile and low-cost strategy for the construction of composite photocatalysts with high-efficiency hydrogen evolution.