Synthesis of Ag@AgBr Photocatalyst and Its Performance for Degradation of Methylene Blue under Visible-Light Irridiation

Ag@AgBr plasmon photocatalyst was prepared by the deposition-precipitation and photo-reduction method. The synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, and UV-Vis diffuse spectroscopy. The photocatalytic activity and stability of the prepared samples were evaluated by the degradation of methylene blue (MB) under the visible light (lambda > 420 nm) irradiation. Several parameters, such as catalyst concentration, pH value, initial MB concentration, H2O2 content, recycling runs, and scavengers, were examined. The results show that the photocatalytic activity of Ag@AgBr reached 96% in MB aqueous solution (10 mg/L) containing 1 g/L catalyst at pH = 9.8 under visible-light irradiation, and it almost kept unchanged after five-cycle photocatalytic test. The degradation efficiency of MB had little variation in the presence of a small amount of H2O2 but reduced in the presence of excessive H2O2. MB photodegradation was greatly suppressed by ethylenediaminetetraacetic acid while slightly decreased by isopropanol. The photocatalytic mechanism for MB degradation by Ag/AgBr under visible light irradiation was also presented.