Synthesis of Au-loaded AgInS2 nanoparticles with highly enhanced visible light photocatalytic performances

AgInS₂ and Au-loaded AgInS₂ (denoted as Au/AgInS₂) were prepared by one-pot method with thioacetamide as sulfur source and mercaptoacetic acid as stabilizer. The structure, morphology, and optical properties of the obtained samples were characterized by XRD, XPS, BET, HRTEM, DLS, PL, and UV–vis-DRS. The photocatalytic activities of AgInS₂ and Au/AgInS₂ for the degradation of Rhodamine B (RhB) and 4-Nitrophenol (4-NP) under visible light irradiation were investigated, and the optimal proportions of Au introduced on AgInS₂ for the degradation of RhB and 4-NP were obtained. The possible degradation mechanisms of 4-NP by AgInS₂ and Au/AgInS₂ were proposed based on the active species trapping experiment, optical properties characterization, and the flat potential determination. The results showed that Au was successfully introduced on the surface of AgInS₂ nanoparticles, and the photocatalytic degradation efficiencies of Au/AgInS₂ toward RhB and 4-NP were higher than those of AgInS₂. 5%Au/AgInS₂ was the optimal proportion for the degradation of RhB, and the degradation efficiency could reach 98% in 30 min, while 7.5%Au/AgInS₂ was the best proportion for the degradation of 4-NP, and the degradation efficiency could reach 100% in 30 min. The enhanced visible light photocatalytic performances of Au/AgInS₂ could be attributed to the stronger visible light absorption and the lower recombination probability of photogenerated electron–hole pairs. Active species trapping experiment suggested that the main active species was superoxide radical (·O₂⁻) for the degradation of RhB by Au/AgInS₂, while for the degradation of 4-NP, the main active species were superoxide radical (·O₂⁻) and hydroxyl radical (·OH).