The synthesis, activity, stability and the charge transfer identification of Ag:AgBr/γ-Al2O3 photocatalyst for organic pollutant decomposition in water

Highly stable Ag:AgBr/γ-Al 2 O 3 photo-catalyst was obtained by dispersing AgBr sol on hollow γ-Al 2 O 3 microsphere. Metallic Ag nanoparticles were in situ generated on AgBr crystals by a photo-reduction method. The activity of catalyst was characterized by MO and phenol decomposition. The light irradiation response, the life times of the photo-induced charges, and the charge separation and transition were determined by the UV–vis diffuse reflection spectra, open circuit voltage decay spectra and transient photocurrent responses. The as-prepared Ag:AgBr/γ-Al 2 O 3 catalyst can response to visible light irradiation. Charge separation was clarified to correlate with electrons transferring from Ag to AgBr surface and the consequent reaction with ads-O 2 to generate O 2 − species. It was found that the O 2 − rather than OH played a dominant role in the photocatalytic oxidation of MO and phenol in water. However, the electrons trended to transfer from AgBr to Ag intrinsically without light irradiation. Therefore, the electron transfer between Ag and AgBr reaching the dynamic equilibrium was the key factor for obtaining a high stable Ag/AgBr catalyst which can be obtained by optimizing the Ag:AgBr ratio. Loading amount of Ag:AgBr on γ-Al 2 O 3 was optimized to 30   wt.% and the metallic Ag content was stabilized at 9   wt.% of Ag:AgBr catalyst.