Synthesis of cubic Ag@AgCl and Ag@AgBr plasmonic photocatalysts and comparison of their photocatalytic activity for degradation of methyl orange and 2,4-dichlorophenol

Uniform cubic Ag@AgCl and Ag@AgBr plasmonic photocatalysts with side length of 0.7 mu m were synthesized by a facile green route, in which a controllable double-jet precipitation technique was employed to fabricate homogeneous cubic AgCl and AgBr grains while a photoreduction process was used to produce Ag nanoparticles (NPs) on the surface of AgCl and AgBr grains. The synthesized samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy (DRS). The photocatalytic activities of Ag@AgCl and Ag@AgBr were compared using degradation of methyl orange (MO) dye and 2,4-dichlorophenol (2,4-DCP) under visible-light irradiation. Ag@AgBr showed higher photocatalytic activity for MO degradation but weaker activity for 2,4-DCP decomposition. Possible degradation mechanisms are proposed to interpret these contrary paradoxical experimental results.