Ternary ZnO/AgBr/Ag2CrO4 nanocomposites with tandem n–n heterojunctions as novel visible-light-driven photocatalysts with excellent activity

Herein, we successfully prepared ternary ZnO/AgBr/Ag2CrO4 nanocomposites with tandem n–n heterojunctions as novel visible-light-driven photocatalysts having excellent activity. The preparation method is a facile and low temperature and employs zinc nitrate, silver nitrate, sodium hydroxide, and potassium chromate as starting materials without using any post-preparation treatments. The resultant samples were characterized using XRD, EDX, SEM, TEM, UV–vis DRS, FT-IR, and PL techniques. The results revealed that weight percent of Ag2CrO4 has substantial influence on degradation of rhodamine B under visible-light irradiation and the best activity was observed for the ZnO/AgBr/Ag2CrO4 (20%) nanocomposite. Photocatalytic activity of this nanocomposite is about 16 and 7-fold higher than those of the ZnO and ZnO/AgBr samples. Increase of the photocatalytic activity was attributed to more harvesting of the visible-light irradiation and efficiently separation of the photogenerated charge carriers due to formation of tandem n–n heterojunctions between counterparts of the nanocomposite. Moreover, the preparation time and calcination temperature significantly affect the photocatalytic activity. Based on the trapping experiments, it was shown that superoxide ions and holes have major influence on the degradation reaction.