Super-high activity of Bi3+ doped Ag3PO4 and enhanced photocatalytic mechanism

Bi-doped Ag 3 PO 4 was synthesized by an ion exchange method, and its structure and properties were characterized systematically. Doping Bi 3+ ions into the crystal lattice of Ag 3 PO 4 changed the properties of particles, reduced the valence band position and widened the band gap of Ag 3 PO 4 . The doped Bi 3+ ions have replaced P 5+ ions of P–O tetrahedrons according to the XRD and XPS analysis. The testing of methyl orange (MO) photodegradation showed that 2 wt% Bi-doped Ag 3 PO 4 had the highest activity, with the degradation rate reaching 90.7% after 6 min (1 g/L catalyst) when pure Ag 3 PO 4 degraded only 27.3% of MO. Its degradation rate constant was 4.5 times that of undoped Ag 3 PO 4 . Particularly, 2 wt% Bi-doped Ag 3 PO 4 managed to photodegrade high-concentration (40 mg/L) MO (1 g/L catalyst), with the degradation rate constant 7.3 times that of undoped Ag 3 PO 4 . •OH radicals were the main active species in the oxidation of MO over Bi-doped Ag 3 PO 4 . Doping Bi 3+ substantially reduced OH defects on the surface of Ag 3 PO 4 , which significantly increased the degradation efficiency of MO over Ag 3 PO 4 . In addition, the density-functional theory calculation revealed that the influence of Bi dopants on the electronic structure may be an important reason for the enhanced photocatalytic performance of Ag 3 PO 4 .