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

Ag3PO4 nanoparticles were lightly deposited on Cu2O cubes, octahedra, and rhombic dodecahedra for facet dependent photocatalytic degradation of methyl orange. Cu2O cubes remain inactive after loading with Ag3PO4. Drastic photocatalytic activity suppression occurs for Ag3PO4-decorated Cu2O octahedra. Surprisingly, total deactivation results for Cu2O rhombic dodecahedra after Ag3PO4 deposition. Electron paramagnetic resonance spectra and electrochemical impendence measurements support the experimental observations. Interfacial Ag3PO4 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.