Ultra-stable visible-light-driven Ag2S/AgI/Ni thin film photocatalyst: Z-scheme photocatalytic mechanism enhances photocatalytic activity

Ag2S/AgI/Ni composite films were prepared by constant current electrodeposition and characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and UV-vis diffuse reflectance spectroscopy. Under visible light (> 420 nm), Ag2S/AgI/Ni composite film photocatalyst showed higher photocatalytic (PC) activity in the degradation of rhodamine B (RhB) than a pure Ag2S/Ni film or AgI/Ni film. The composite film demonstrated excellent stability and could be recycled 11 times with an essentially unchanged PC activity. Ag nanoparticles were generated in the PC process and acted as a charge-transfer bridge, forming a Z-scheme composed of Ag2S, Ag, and AgI. This effectively separated the photogenerated electrons and holes, hence providing excellent PC activity and stability to the Ag2S/AgI/Ni composite film.