Enhanced photocatalytic performance of ZnO/AgCl composites prepared by high-energy mechanical ball milling

Photocatalytic oxidation plays an important role in pollutant degradation and organic synthesis. In this study, a series of ZnO/AgCl composites were prepared using the high-energy mechanical ball-milling method and characterized using XRD, TEM, SEM, DRS and XPS. Under visible light irradiation (lambda >= 400 nm), the photocatalytic activity of ZnO/AgCl composites (BM-ZA) prepared by ball-milling was examined for the degradation of rhodamine B (RhB) and dehydrogenation of diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate (1,4-DHP). The photocatalytic activity enhancement of BM-ZA composites is associated with the content of AgCl. The catalytic efficiency of BM-ZA-60% composite was 38.4 and 7.7 times higher than those of ZnO and AgCl for the photodegradation of RhB, and 16.6 and 11 times higher than those of ZnO and AgCl for the photodehydrogenation of 1,4-DHP, respectively. Furthermore, the photocatalytic activity of the BM-ZA-60% photocatalyst was also higher than those of the counterparts of ZnO/AgCl mixture (SM-ZA-60%) and ZnO/AgCl composite (DP-ZA-60%) prepared by deposition-precipitation. The photocatalytic activity enhancement of BM-ZA composites may be due to the formation of a heterojunction between the surfaces of ZnO and AgCl, which facilitates the separation of the photoinduced electron-hole pairs and thus improves the photocatalytic capacity. Finally, a possible photocatalytic reaction mechanism was proposed based on the photoelectrochemical measurements and free radical capture experiments.