Solar photocatalytic performance of glass substrates coated with Ag3PO4 thin films

Abstract

Silver-orthophosphate (Ag3PO4) photocatalysts exhibit excellent photo-oxidative capabilities under visible light irradiation, especially in their powders form. However, Ag3PO4 in the form of thin films has not been explored that much and very little is known about their performance under solar irradiation. In the present study, glass substrates were coated with Cu-doped Ag3PO4 (Cu-Ag3PO4) and Ag3PO4 thin films using successive ionic layer adsorption and reaction (SILAR) due to its simplicity, relatively low-cost and ability to be performed at low temperatures with low time requirements. The as-deposited thin films were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and UV–Visible spectrophotometry, while their photocatalytic performances were evaluated on Rhodamine-B (Rh-B) dye degradation under real solar light irradiation. The adopted coating protocol resulted in regular thin films that crystallize in the desired P4̅3n cubic phase, where doping with Cu was shown to be responsible of a crystallite size reduction within the film. From the optical point of view, a broad absorbance in the entire visible range was obtained with bandgap energies of about 2.2 eV in the case of Ag3PO4 thin films, and around 1.65 eV in the case of Cu-Ag3PO4 thin films. Such optical features were exploited to test the photocatalytic performance in the degradation of Rh-B dye. After 4 h of solar irradiation, the variation of the relative concentration of Rh-B solution relative to the degradation efficiency of the photocatalysts was of 54% in the case of Cu-Ag3PO4 thin films and of 89% in the case of Ag3PO4 thin films. So, exploration of a wide area of the solar visible spectrum is made possible under doping, a finding that would improve the overall photocatalytic activity which is very promising for the degradation of other organic pollutants under solar irradiation.