Visible photocatalysis and photostability of Ag3PO4 photocatalyst

•We systematically investigated the photocatalytic characteristics of Ag3PO4.•Ag3PO4 cannot photodegrade volatile organic compounds such as benzene, acetone.•Ag3PO4 is efficient for dye photodegradation rather than dye photomineralization.•Ag3PO4 itself is photostable but quickly deactivate during dye photodegradation. Ag3PO4 photocatalyst was prepared by precipitation method and characterized by SEM, XRD and diffusive reflectance UV–vis (DRUV–vis) absorption spectra. The gas-phase photodegradation of volatile organic compounds (VOCs) such as benzene and acetone, and the liquid-phase photodegradation of the cationic and anionic dyes on Ag3PO4 were systematically investigated. Both benzene and acetone could not be photodegraded on the Ag3PO4 photocatalyst under the visible irradiation. The Ag3PO4 photocatalyst is efficient for the photodegradation of the aqueous dye solutions, but could not completely photomineralize the dyes to CO2 and H2O. The reason is discussed by comparing the oxidation potential of organic pollutants and the potential of photogenerated holes in Ag3PO4, and measuring the absorption of organic pollutants on Ag3PO4. The photostability of the Ag3PO4 photocatalyst for the photo-degradation of the dyes was tested. The Ag3PO4 photocatalyst itself is photostable in the absence of the scavenger of the photogenerated holes, but is photocatalytically instable in the liquid-phase photodegradation of dyes due to the photoreduction of Ag+ in Ag3PO4 to Ag.