Photocatalytic degradation and electricity generation in a rotating disk photoelectrochemical cell over hierarchical structured BiOBr film

Abstract

A double hierarchical structured BiOBr film was prepared on Ti substrate through hydrolysis of Bi2O3 film in the presence of Br− and H+. The prepared BiOBr film exhibited much better photocatalytic (PC) activity on Rhodamine B (RhB) degradation than Bi2O3 film in a rotating disk PC reactor. The double hierarchical structure could not only enhance the surface area, but also exhibited strong RhB adsorption capacity and high light utilization efficiency due to multiple reflections of incident light. Due to similar hierarchical structure, BiOCl film was also used to compare the PC activity of BiOBr film. Because the band gap energy of BiOBr (2.5eV) was narrower than that of BiOCl (3.2eV), weaker PC activity was obtained for BiOBr film under UV light. However, besides RhB photosensitization degradation, BiOBr could also be excited by part of visible light to generate •OH, resulting in a better RhB removal under visible light. A Pt cathode was further connected to BiOBr/Ti photoanode to establish a rotating disk BiOBr/Ti–Pt photoelectrochemical cell to generate electricity with the degradation of pollutants simultaneously. 0.77 and 0.74V open-circuit voltage, 0.019 and 0.010mAcm−2 short-circuit current density were obtained under UV and visible light irradiation, respectively, with 50mL5mgL−1 RhB as “fuel”. The PC activity was also improved due to the efficient separation of electrons and holes. The total current generated was stable but gradually decreased with treatment time due to the consumption of “fuel”.