Fabrication of visible-light-active Bi/BiOI-Bi₂O₃ composite with enhanced photocatalytic activity

Plasmonic Bi⁰ modified BiOI-Bi₂O₃ composite (Bi/BiOI-Bi₂O₃) was prepared via in situ UV reduction method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) techniques were carried out to identify the formation of semimetal Bi⁰. The results indicated that the dot-like bismuth particles were originated from the partial reduction of lattice Bi³⁺ to Bi⁰ by accumulated conduction band electrons in BiOI-Bi₂O₃. The as-prepared ternary composite exhibited enhanced visible-light-response, decreased charge transfer impedance and higher charge carrier density relative to unmodified BiOI-Bi₂O₃. Due to synergistic effect between plasmonic Bi⁰ and BiOI-Bi₂O₃ heterojunction, dramatically enhanced photocatalytic activity for phenol degradation can be achieved. After 3.5 h visible light irradiation, the value for phenol removal efficiency was ca. 60% and 100% on BiOI-Bi₂O₃ and Bi/BiOI-Bi₂O₃, respectively. The calculated zero-order rate constant on Bi/BiOI-Bi₂O₃ was 1.7 and 3.9 times that on BiOI-Bi₂O₃ and Bi₂O₃, respectively. In addition to phenol, organic dyes (zwitterionic RhB, cationic MB and anionic Org II) were also used as model pollutants. Pronounced photocatalytic degradation by Bi/BiOI-Bi₂O₃ can be observed, further confirming the importance of Bi⁰. Trapping experiments using different scavengers indicated that photogenerated holes were major active species during the degradation of phenol. Furthermore, good stability was also observed in 5 successive cyclic runs. This study opens a new strategy for in situ preparation of plasmonic Bi⁰ modified composite.