Microstructure-dependent photoelectrocatalytic activity of heterogeneous ZnO–ZnS nanosheets

Abstract

Abstract ZnS crystallite-loaded ZnO sheet composites were successfully synthesized through vulcanization of hydrothermally derived porous ZnO sheet templates. The sulfur precursor (Na2S: 0.05–0.25 M) concentration affects the ZnS loading content and surface morphology of the ZnO–ZnS composites. A higher sulfur precursor concentration increased the ZnS loading content and decreased the porosity of the ZnO–ZnS composites. The ZnO–ZnS sheet composites with the atomic composition ratio of ZnO larger than that of the decorated ZnS exhibited an enhanced photoactivity. By contrast, the overloading of ZnS crystallites on the ZnO template decreased photoactivity. The ZnO–ZnS sheet composite with a S/O atomic ratio of 0.61 exhibits the highest photoactivity among various samples. The enhanced charge separation efficiency because of the formation of ZnO/ZnS heterojunctions and porous structure allowed the synthesis of the ZnO–ZnS composite via hydrothermal vulcanization with 0.05 M Na2S, and shows the higher photoelectrochemical (PEC) degradation ability towards Rhodamine B solution among various samples. The scavenger tests and the proposed PEC-degradation mechanism demonstrate that superoxide radicals are the main active species for the degradation of the RhB solution. The experimental results herein show that the porous ZnO–ZnS sheet composite with a suitable phase ratio is promising for photoelectrocatalyst applications.