Enhanced Photocatalytic Activity of Nanoparticle-Aggregated Ag-AgX(X = Cl, Br)@TiO Microspheres Under Visible Light.

Ag-AgX(X = Cl, Br)@TiO nanoparticle-aggregated spheres with different mass ratio of  = TiO/Ag(X) from 35:1 to 5:1 were synthesized by a facile sol-gel technique with post-photoreduction. The photocatalytic activities of both Ag-AgCl@TiO and Ag-AgBr@TiO under visible light are effectively improved by ~3 times relative to TiO NPAS under the simulated sunlight for the decomposition of methyl orange (MO). Ag-AgBr@TiO showed 30% improvement and less stable in photocatalytic activity than that of AgCl@TiO. The role of Ag and AgX nanoparticles on the surface of Ag-AgX(X = Cl, Br)@TiO was discussed. Ag on these samples not only can efficiently harvest visible light especially for AgCl, but also efficiently separate excited electrons and holes via the fast electron transfer from AgX(X = Cl, Br) to metal Ag nanoparticles and then to TiO-aggregated spheres on the surface of heterostructure. On the basis of their efficient and stable photocatalytic activities under visible-light irradiation, these photocatalysts could be widely used for degradation of organic pollutants in aqueous solution.