Enhanced visible-light photocatalytic performances of Ag₃PO₄ surface-modified with small amounts of TiO₂ and Ag

Graphical abstract: - Highlights: • An efficient photocatalyst was prepared by surface-modifying Ag₃PO₄. • The surface-modified Ag₃PO₄ possesses high visible-light photocatalytic performances. • The surface-modification can decrease the solubility of Ag₃PO₄ in water environment. - Abstract: A novel approach has been developed to prepare an efficient visible-light photocatalyst using Ag₃PO₄ and TiO₂ sol as precursors. First, Ag₃PO₄ particles were dipped into TiO₂ sol for 5 min and were filtered quickly. Second, Ag₃PO₄ particles adsorbing a small amount of TiO₂ sol were aged for 24 h to form TiO₂ gel on their surface. Finally, Ag₃PO₄ particles covered by TiO₂ gel were calcined at 450 °C for 2 h to obtain the surface-modified Ag₃PO₄ sample. The surface-modified Ag₃PO₄ was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, UV–vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. The visible-light photocatalytic performances of the surface-modified Ag₃PO₄ were evaluated by the photodegradation of methyl orange or phenol solution. The results showed that the surface-modified Ag₃PO₄ exhibited much higher visible-light photocatalytic activity and stability than pure Ag₃PO₄. As the amount of TiO₂ gel on the Ag₃PO₄ surface increased, the visible-light photocatalytic activity increased first and then decreased. The surface-modification of Ag₃PO₄ obviously decreased its solubility in water environment due to the protection of TiO₂ and Ag nanocrystals on the surface. The visible-light photocatalytic mechanism of the surface-modified Ag₃PO₄ has been discussed