Band engineering of ZnO/Si nanowire arrays in Z-scheme heterojunction for efficient dye photodegradation

摘要

Hierarchical heterogeneous ZnO/Si nanowire arrays grown from metal-induced wet etching process on p-type silicon wafer were obtained and have been strategically sensitized by narrow bandgap semiconductors of In2S3 nanosheets and Ag2S quantum dots via successive ionic layer adsorption and reaction technique. The photo degradation of methylene blue as catalyzed by the arrays was conducted under visible light and ultraviolet light. By introducing the coating layers, the specimens were found to achieve absorptivity higher than 94% and yield a quarter of the resistance and 31-fold of the photo-current as compared to the primary nanowire arrays. The photodegradation efficiency was improved from 48.9% to 62.0%, and 43.0% to 55.0%, respectively in visible light and ultraviolet light with an enhanced recyclability. Band structure analysis indicated that the coating brought different Z-scheme heterojunctions for efficient photocatalytic performance, while the function could only work in a given spectral range. These results would be helpful to better realize the photocatalytic mechanisms and meanwhile, could be extended to design heterogeneous semiconductor nanomaterials for their potential applications.