Facile synthesis, characterization and photocatalytic activity of Ag₃PO₄/Ag₂W₂O₇ heterojunction composite

A series of Ag₃PO₄/Ag₂W₂O₇ heterojunction composite photocatalyst with ascending Ag₂W₂O₇ content (W loading 0–30%) were synthesized through one-shot coprecipitation technique and characterized by XRD, SEM, Raman and DR UV–Vis spectroscopy. The photocatalytic activity of the synthesized samples was evaluated by the photocatalytic decolorization of methyl orange (MO) dye under visible light illumination and compared with that of neat Ag₃PO₄. Ag₃PO₄/Ag₂W₂O₇ heterojunction composite with W loading 10% exhibited the highest photocatalytic activity, in which 65% of MO was decolorized after 10 min, versus 9% in the case of neat Ag₃PO₄. Moreover, the apparent rate constant of MO decolorization in the case of Ag₃PO₄/Ag₂W₂O₇ composite was 7.2 times higher than neat Ag₃PO₄. However, Ag₃PO₄/Ag₂W₂O₇ heterojunctions with W loadings exceeding 10% showed lower photocatalytic efficiency, most likely, due to increasing Ag₂W₂O₇ content in the composite which shields Ag₃PO₄ surface and restricts the photocatalytic process. The enhancement in the photocatalytic activity of the prepared samples was attributed to the effective separation of photogenerated electron-hole pairs as a result of the formed heterojunction between Ag₃PO₄ and Ag₂W₂O₇ in the composite. The formed Ag₃PO₄/Ag₂W₂O₇ heterojunction showed a shift of the optical absorption edge of Ag₃PO₄ to longer wavelengths. Thus, it can be concluded that Ag₃PO₄/Ag₂W₂O₇ heterojunction composite with W loading of 10% is a promising photocatalyst in visible light illumination for industrial wastewater treatment. (paper)