Synthesis of Zn²⁺ doped AgIn_xS_y sub-microspheres and its visible light photocatalytic activity

AgIn_xS_y and Zn²⁺ doped AgIn_xS_y sub-microspheres (denoted as Zn–AgIn_xS_y) were synthesized by one-pot method. The visible light photocatalytic activity of the as-synthesized sample was investigated through photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation. The experimental result shows that the as-synthesized AgIn_xS_y is face-centered cubic phase AgIn₅S₈ when the ratio of Zn to In is < 4:13, while the sample changed from AgIn₅S₈ to orthorhombic phase AgInS₂ gradually when the ratio of Zn to In increased to 9:8. Doping of Zn²⁺ increased the regularity, dispersibility, and visible light absorption of AgIn_xS_y. As a result, the visible light photocatalytic activity of Agln_xS_y is improved obviously. The optimum ratio of Zn to In is 4:13, Zn–Agln_xS_y with the optimal ratio showed the highest visible light photocatalytic activity. The possible mechanism of degradation of RhB by Agln_xS_y and Zn–Agln_xS_y was proposed by carrying out the active species trapping experiments. The results suggested that the degradation of RhB by Agln_xS_y is mainly due to hydroxyl radical (^·OH), while the degradation by Zn–Agln_xS_y is mainly due to superoxide radical (^·O₂⁻).