Fabrication of AgO/WO p-n heterojunction composite thin films by magnetron sputtering for visible light photocatalysis.

Semiconductor-based nanostructures which are photo-catalytically active upon solar light irradiation were extensively used for environmental remediation due to the potential decomposition of various kinds of pollutants. In this work, we report the preparation of a sustainable thin film composite, AgO/WO p-n heterojunction, and investigation of its photocatalytic activity. To achieve the composite structure, WO/Ag-WO layers were deposited over a quartz substrate by magnetron sputtering at room temperature and subsequently annealed at 823 to 923 K. The thin film structure, morphology, and chemical states were thoroughly characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron spectroscopy, and X-ray photoelectron spectroscopy. The obtained results revealed that the amorphous Ag-doped WO was crystallized into monoclinic WO and AgO, in which nanocrystalline AgO was diffused towards the surface of WO. Optical transmittance spectra recorded by UV-vis-NIR spectroscopy revealed that the WO/Ag-WO films became transparant in the visible region after annealing at high temperature (873 K and 923 K). The AgO/WO p-n heterojunction composite thin films showed high photocatalytic activity (0.915 × 10 min) under visible light irradiation, which is attributed to the efficiency of effective photogenerated charge-carrier formation and the reduced recombination rate of photogenerated electron-hole pairs. Unlike the powder-based photocatalysts, the reported thin film-based heterojunction photocatalyst could be very sustainable, and cost-effective.