Charge trapping and transfer mechanisms of noble metals and metal oxides deposited Ga2O3 toward typical contaminant degradation

Ga2O3 highlights the high energy band structure for redox reaction. However, information on noble metals and metal oxides deposited Ga2O3 for contaminant elimination and the corresponding mechanisms is still lack. Here, metals and metal oxides deposited Ga2O3 (labeled as M-P and MO-C; M = Ag, Pt, and Pd) were synthesized by photocatalytic and chemical deposition methods and confirmed with XRD and XPS. M-P and MO-C were applied in photocatalytic degradation of three typical contaminants: ciprofloxacin, ronidazole and rhodamine B. The ciprofloxacin and ronidazole degradation rates by Ag2O-C and rhodamine B degradation rate by Ag-P were 3.0, 2.7 and 2.4 times as high as those by pure Ga2O3. This research demonstrates that photocatalytic activities of M-P and MO-C are affected by the types and oxidation states of noble metals, as well as the target contaminants. Potentials of M or MO (E(MΦ) or E(MOCB), defined as work function of the metals or conduction band of the metal oxides) is the determining factor for both charge trapping and charge transfer abilities. The highest photocatalytic activity can be obtained when the E(MΦ) or E(MOCB) was kept at the level just beyond the single electron reduction potential of O2, such as Ag-P and Ag2O-C. Finally, the contaminants-specific photocatalytic activities were related to the different functional reactive species. Findings of this study provide important information for the rational design of M and MO deposited photocatalysts.