Iodide-modified Bi4O5Br2 photocatalyst with tunable conduction band position for efficient visible-light decontamination of pollutants

Band-gap regulation of photocatalysts has been turned out to be a very important approach to achieve high effective utilization of solar spectrum and obtain an optimal photocatalytic property. Herein, a novel iodide modified Bi4O5Br2 photocatalyst with controlled band-gap position was successfully synthesized for the first time via a simple alcoholysis-hydrolysis method at room temperature. The band structure, optical absorption properties, photo-induced charges transfer/separation rate of the synthesized samples were characterized by UV-vis DRS, Mott-Schottky method, valence band (VB) XPS, electrochemical impedance spectra and photoelectric conversion spectra. The results demonstrated that the conduction band position of Bi4O5Br2 continuously decreased from 2.46 eV to 2.16 eV, and then the visible-light response and photo-generated carrier separation changes took place. Owing to the higher visible-light absorption capacity, lower interfacial charge-transfer resistance, and more efficient separation of the photoinduced charges, the iodide modified Bi4O5Br2 exhibited a higher visible-light activity than pure Bi4O5Br2 for the photocatalytic degradation of Bisphenol A (BPA) and NO removal under visible light irradiation. Ultimately, the repeated photodegradation experiments of BPA displayed that the obtained sample is stable and resistant to chemical or photochemical corrosion. We believe such a simple and effective strategy could pave a new way for narrowing continuously the band gap of an existed photocatalyst to control the generation and recombination rate of photo-induced carriers.