Sonosynthesis of an Ag/AgBr/Graphene-oxide nanocomposite as a solar photocatalyst for efficient degradation of methyl orange.

In this study, a new method has developed for the synthesis of Ag/AgBr/Graphene-oxide (Ag/AgBr/GO) nanocomposite with high adsorption capacity and high photocatalytic activity in degradation of methyl orange (MO). In this method, ultrasound was applied in the synthesis and it was facilitated the process. The samples prepared under ultrasound were shown as Ag/AgBr/GO-U, and the samples under conventional method as Ag/AgBr/GO-C. The results of FT-IR, XRD, Raman, DRS and SEM confirmed the structure of the nanocomposites very well. Ultrasound played a key role in the formation of nanocomposite with smaller size of GO sheets and particles. Different amount of GO was used in the nanocomposite composition and their photocatalytic activities were compared. The MO in solution was completely degraded in 15 min, 30 min, and 45 min with Ag/AgBr/GO-U-1 that contained 1 mg mL(-1) GO, Ag/AgBr/GO-U-0.5 that contained 0.5 mg mL(-1) GO and Ag/AgBr/GO-C-0.5 that contained 0.5 mg mL(-1) GO, respectively. The chemical oxygen demand (COD) measurements displayed a complete mineralization in 30 min for Ag/AgBr/GO-U-0.5. The data obtained from the degradation experiments were fitted to the first-order kinetics and the adsorption obeyed the Langmuir model. The nanocatalyst did not exhibit significant loss of activity even after four cycles of successive uses. To determine the mechanism of photocatalytic degradation of MO, different scavengers were used. Based on the results, the superoxide radical, hydroxyl radical and hole had a key role in the degradation process. The Ag/AgBr/GO-U-1 nanocomposite exhibited the highest photocatalytic activity due to its high adsorption capacity and enhanced charge transfer.