Construction of iodine vacancy-rich BiOI/Ag@AgI Z-scheme heterojunction photocatalysts for visible-light-driven tetracycline degradation: Transformation pathways and mechanism insight

Constructing highly efficient visible-light-driven (VLD) photocatalysts for organic pollutants degradation has been unearthed as a promising and green strategy on environmental remediation. In this study, a novel iodine vacancy-rich BiOI/Ag@AgI (Ag@AgI/VI-BOI) Z-scheme heterojunction photocatalyst was successfully constructed, where Ag@AgI nanoparticles in-situ grown on the surface of defective BiOI nanosheets. The morphology and structure, optical, photoluminescence, and photo-electrochemical properties of the photocatalysts were detailedly characterized. Tetracycline (TC) as a refractory antibiotic was chosen as target pollutant to evaluated the photocatalytic performance of the Ag@AgI/VI-BOI photocatalyst. The Z-scheme Ag@AgI/VI-BOI photocatalyst possessed significantly boosted photocatalytic efficiency for the degradation of TC under visible light irradiation (λ > 420 nm), which was better than that of BiOI, VI-BOI, and Ag@AgI. The impacts of photocatalyst dosages, initial TC concentrations, inorganic anions and light irradiation conditions on TC degradation were also explored. Importantly, the intermediates and possible decomposition pathways of TC were illustrated through liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and three-dimensional excitation-emission matrix fluorescence spectroscopy (3D EEMs) analysis. The enhanced photocatalytic activity of the Ag@AgI/VI-BOI is attributed to the synergetic effect among iodine vacancies, AgI/VI-BOI heterojunction and metallic Ag0. Additionally, the photocatalyst presented high recyclability and stability. This work can afford a new reference for fabricating photocatalyst with synergistic effect and amazing capacity for practical wastewater treatment.