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

Plasmonic Bi modified BiOI-BiO composite (Bi/BiOI-BiO) 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 Bi. The results indicated that the dot-like bismuth particles were originated from the partial reduction of lattice Bi to Bi by accumulated conduction band electrons in BiOI-BiO. The as-prepared ternary composite exhibited enhanced visible-light-response, decreased charge transfer impedance and higher charge carrier density relative to unmodified BiOI-BiO. Due to synergistic effect between plasmonic Bi and BiOI-BiO 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-BiO and Bi/BiOI-BiO, respectively. The calculated zero-order rate constant on Bi/BiOI-BiO was 1.7 and 3.9 times that on BiOI-BiO and BiO, 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-BiO can be observed, further confirming the importance of Bi. 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 Bi modified composite.