Photocatalytic Activity Suppression of Ag₃PO₄-Deposited Cu₂O Octahedra and Rhombic Dodecahedra

Ag 3 PO 4 nanoparticles were lightly deposited on Cu 2 O cubes, octahedra, and rhombic dodecahedra for facet-dependent photocatalytic degradation of methyl orange. Cu 2 O cubes remain inactive after loading with Ag 3 PO 4 . Drastic photocatalytic activity suppression occurs for Ag 3 PO 4 -decorated Cu 2 O octahedra. Surprisingly, total deactivation results for Cu 2 O rhombic dodecahedra after Ag 3 PO 4 deposition. Electron paramagnetic resonance spectra and electrochemical impendence measurements support the experimental observations. Interfacial Ag 3 PO 4 lattice planes have been identified. A modified band diagram is constructed to understand photocatalytic activity decay or deactivation because of large interfacial band bending to create an unfavorable situation for charge carrier transport across the heterojunctions. This study further illustrates that photocatalytic suppression can be often observed in many semiconductor heterojunctions and multiple interfacial plane combinations mean that photocatalytic outcomes are unpredictable.