Enhanced photoelectrochemical performance of ZnO nanorod arrays decorated with CdS shell and Ag_2S quantum dots

摘要

Ternary nanostructured Ag_2S/CdS/ZnO thin film was prepared by using a simple low-cost hydrothermal method. The hexagonal phase of ZnO nanorods and CdS shells combined with monoclinic Ag_2S quantum dots resulted in improved optical and photo-electrochemical properties. CdS shell with high absorption property efficiently compliment the energy levels of ZnO and improved the ability of light absorption. Furthermore, narrow band gap Ag_2S also played a vital part in the light harvesting. The photoelectrochemical performance of the ternary nanostructured Ag_2S/CdS/ZnO NRs was investigated in a mixture of Na_2S and Na_2SO_3 aqueous solutions under visible light illumination. The Ag_2S/ CdS/ZnO NRs were found to be more efficient than ZnO NRs, CdS/ZnO NRs, and Ag_2S/ZnO NRs as this particular sample gave a maximum photocurrent of 5.69 mA cm~(-2), which is around 2 and 1.5 times greater than CdS/ZnO NRs and Ag_2S/ZnO NRs, respectively. Besides that, it was found that this ternary film possessed 15 times higher photocurrent density than plain ZnO NRs. This is attributed to the larger amount of visible light absorbed by the ternary nanostructured composite.