Study On Preparation And Performance Of Novel Bi₂O₃-BiPO₄and Bi₂O₃-BiOI Photocatalysts

Since the photoelectrocatalytic technology exhibits significant prospects in coping with the serious energy and environment problems, the development of efficient and practical visible light-responsive photocatalyst remains a great challenge.A novel heterojunction of p-n type Bi2O3-BiPO4electrode was successfully synthesized by the method of electrophoretic deposition. The result of X-ray diffractometer and scanning electronic microscopy indicated that the cubic Bi2O3and monoclinic BiPO4were coexisted in the Bi2O3-BiPO4composites. In the photoelectrochemical (PEC) measurements, the Bi2O3-BiPO4composite shows significantly improved photocatalytic activity and photostability over the pure Bi2O3or BiPO4film. In addition, the p-n type Bi2O3-BiPO4electrode also exhibit higher efficiency of charge transfer and separation of photogenerated charge. The possible mechanism of the enhanced photocaltalytic activity was discussed. PEC degradation of phenol was carried out using Bi2O3-BiPO4and films as the photoanodes to test the PEC performances of composite. The PEC degradation efficiency of the composite was2times higher than the pure Bi2O3films. The acidic solution was favorable for the PEC degradation of phenol and the PEC degradation achieved the best efficiency when the pH of the solution was adjusted to3. The PEC reaction rate of phenol increased with the enhancement of the applied voltage. The recycle experiments of Bi2O3-BiPO4film in PEC degradation showed the composite film had the good performance of stability.Bi2O3-BiOI film was synthesized by a simple dipping method. The BiOI film could successfully grow on the baisis of Bi2O3at room temperature and showed the morphology of cross-flake arrays. In the cases of PEC performance, the photocurrent density of the formed Bi2O3-BiOI composite increased by ca.11times relative to the pure Bi2O3film at0.35V vs. Ag/AgCl in0.2mol/L Na2SO4aqueous solution under visible light irradiation. The Nyquist diagram and the IPCE spectrum indicated that significantly enhanced transfer and separation efficiency of electron-hole pairs in the Bi2O3-BiOI composite film. Possible mechanism of the enhanced photocaltalytic activity was discussed. BiOI could be excited by visible light easily. Once BiOI was excited, electrons in the VB of BiOI could be excited up to a higher potential edge due to the higher photon energy. This process made photoelectrons separate more efficient and reduced the recombination rate of photogenerated electron-hole on the Bi2O3-BiOI interface. Therefore, Bi2O3-BiOI composite could exhibit better PEC activity than that of pure BiOI and Bi2O3films.The phenol and Cr(VI) were used as the model pollutants to evaluate the degradation performance of the Bi2O3-BiOI composite films, respectively. In the PEC degradation of phenol or Cr(VI) under visible light irradiation, the PEC efficiency of the Bi2O3-BiOI composite exhibit a great increase compared with Bi2O3films, and a significant synergetic effect was concluded between PC process and EC process. On the other hand, the composite film had the good performance of stability during the process of the recycle of Bi2O3-BiPO4film in PEC degradation of phenol or Cr(VI).