Enhanced visible light photocatalytic performance of ZnO nanowires integrated with CdS and Ag2S.

A series of ZnO–CdS–Ag2S ternary nanostructures with different amounts of Ag2S were prepared using simple and low-cost successive ionic layer adsorption and reaction (SILAR) and a chemical precipitation method. The ZnO nanowires, with a diameter of ∼100 nm and a length of ∼1 μm, were modified by coating CdS and Ag2S. CdS has a high absorption coefficient and can efficiently match with the energy levels of ZnO, which can enhance the light absorption ability of the nanostructures. In addition, Ag2S with a narrow band gap was used as the main light absorber and played an important role in increasing the light absorption in the visible light region. The photocatalytic activity of the ZnO–CdS–Ag2S ternary nanostructures was investigated using the degradation of methyl orange (MO) in an aqueous solution under visible light. The ZnO–CdS–Ag2S ternary nanostructures were found to be more efficient than ZnO nanowires, ZnO–CdS nanowires, and ZnO–Ag2S nanowires. There is 7.68 times more photocatalytic activity for MO degradation in terms of the rate constant for ZnO–CdS–Ag2S 15-cycle ternary nanostructure compared to the as-grown ZnO. Furthermore, the effect of the amount of Ag2S and CdS on the ZnO surface on the photocatalytic activity was analyzed. The superior photo-absorption properties and photocatalytic performance of the ZnO–CdS–Ag2S ternary nanostructures can be ascribed to the heterostructure, which enhanced the separation of the photo-induced electron–hole pairs. In addition, visible light could be absorbed by ZnO–CdS–Ag2S ternary nanostructures rather than by ZnO.