Effective photocatalytic salicylic acid removal under visible light irradiation using Ag2S/AgI-Bi2S3/BiOI with Z-scheme heterojunctions

A photocatalyst of Ag₂S/AgI-Bi₂S₃/BiOI was synthesized with Z-scheme heterojunctions simply by the S²⁻-I⁻ anion exchange route showing broad visible light response and enhanced photogenerated carriers properties. The yielded Ag₂S/AgI-Bi₂S₃/BiOI could feature the reactive active sites of Bi₂S₃/BiOI and Ag₂S/AgI heterojunctions, serving as the photogenerated electron donors and photogenerated electron acceptors, respectively. Ag bridges were generated to ensure the construction of Z-scheme strategy, which further improved the migration direction of charge carriers in nanocomposites. Moreover, the analysis of photoluminescence spectra and electrochemical impedance spectroscopy could testified the functions of heterojunctions, which dramatically achieved the enhanced separation and transferring capacity of photogenerated electron-hole pairs in photocatalyst, respectively. In addition, Ag₂S/AgI-Bi₂S₃/BiOI with large specific surface area facilitated the efficient photocatalytic removal of salicylic acid (SA) (up to 89.2%) under visible light. Favorable photocatalytic production of hydrogen peroxide (H₂O₂) were obtained in pure water driven by the visible light. Besides, by the results of capture experiments, DMPO spin trapping ESR spectra and band structures analysis, the Z-scheme manner of the nanocomposites could promote the reduction ability of photo-generated electrons so as to produce numerous ·O₂⁻ during the photocatalytic reactions toward the photocatalytic SA removal and H₂O₂ production.