Plasmon-Assisted Degradation of Toxic Pollutants with Ag-AgBr/Al2O3 under Visible-Light Irradiation

AgBr coated with silver (Ag) nanoparticles (NPs) were highly dispersed on ordered mesoporous gamma-Al2O3 (MA) by the deposition-precipitation method with surfactant (Ag-AgBr/MAP). The catalyst showed high and stable photocatalytic activity for the degradation and mineralization of toxic persistent organic pollutants, as demonstrated with 2-chlorophenol (2-CP), 2,4-dichlorophenol, and trichlorophenol under visible light or simulated solar light irradiation. The dispersion of Ag-AgBr NPs on MA strongly affected their photoactivity. On the basis of electron spin resonance and cyclic voltammetry analyses under a variety of experimental conditions, two plasmon-induced electron-transfer processes were verified from the excited Ag NPs to AgBr and from 2-CP to the Ag NPs, resulting in O-2(center dot-) and excited h(+) on Ag NPs. Also, (OH)-O-center dot and O-2(center dot-) were formed by photoexcited AgBr. Both (OH)-O-center dot and O-2(center dot-) radicals were primary active species, whereas the excited h(+) on Ag NPs was involved in the photoreaction system of Ag-AgBr/MAP. The highly efficient degradation of pollutants came from both photoexcited AgBr and plasmon-excited Ag NPs. Accordingly, the plasmon-induced electron-transfer processes elucidated the photostability of Ag-AgBr/MAP. These findings indicate potential applications of noble metal NPs in the fields of developing visible-light-sensitive photocatalysts and photovoltaic fuel cells.