Ag₃PO₄ Oxygen Evolution Photocatalyst Employing Synergistic Action of Ag/AgBr Nanoparticles and Graphene Sheets

A graphene-supported Ag 3 PO 4 /Ag/AgBr water oxidation photocatalyst was prepared by a photoassisted deposition–precipitation reaction, followed by a hydrothermal treatment. The composite photocatalyst exhibits double the O 2 -production activity than that of bare Ag 3 PO 4 under visible light irradiation. Moreover, it exhibits enhanced activity in comparison to unsupported Ag 3 PO 4 /Ag/AgBr, to graphene-supported bare Ag 3 PO 4 powder as well as to Ag/AgBr powder. This increase in activity is attributed to a combination of depletion of the conduction band of the as-synthesized n-doped Ag 3 PO 4 material and a downshift of the Ag 3 PO 4 valence band due to the pinning of its conduction band at the silver Fermi level, a process that is assisted by charge transfer and distribution onto the graphene support.