Synthesis And Photocatalytic Activity Of Bismuth-based Photocatalyst

With the rapid development of the industrial and the increasing number of population, environmental pollution and critical energy shortage have become the main barriers for social development. In recent years, the rapid development of photocatalytic technology may provide an efficiency way to overcome these two problems. Among them, the bismuth-based photocatalyst as a new photocatalytic material, because of their unique layered structure, efficient photocatalytic activity, good stability, non-toxic, low cost and other advantages, has attracted continued attention. As a promising photocatalyst, it will have a vast development prospecct in the field of solar energy conversion and environmental remediation. Based on the characteristic of Bismuth-based semiconductor photocatalysts, in this paper, three types of Bismuth-based composite materials(IL-BiPO4, BiPO4/graphene/MoS2, Ti O2-Bi2WO6) were synthesized, and their photocatalytic activities were studied by the degradation of the RhB solution. The prepared samples were characterized by XRD, SEM, TEM, BET, XPS, PL techniques. The relationships between the structure and photocatalytic performance were also investigated.(1) Hierarchical flower-like BiPO4 microspheres were successfully synthesized by reacting bismuth nitrate with [Bmim]PF6(1-butyl-3-methylimidazolium hexafluorophosphate) in water at 160 oC via a microwave-assisted hydrothermal route, where the ionic liquid could act as phosphorus source, surface modified agent and template. On degradation of Rhoda mine B aqueous solution under UV light irradiation, the ionic liquid modified BiPO4(IL-BiPO4) exhibited significantly enhanced photocatalytic activity in comparison with the unmodified counterpart prepared in the absence of [Bmim]PF6. The effects of ionic liquid modification on the photocatalytic activity enhancements and the photocatalysis mechanism of IL-BiPO4 were systematically investigated. The results suggested that ionic liquid modification could trap the photoinduced electron at conduction band of BiPO4 and effectively improved the separation efficiency of photoinduced electron-hole pairs, which then could enhance its photocatalytic activity on the degradation of organic pollutants.(2)Graphene and MoS2 nanosheets modified BiPO4 nanoparticles were successfully prepared by a microwave-assisted hydrothermal route. The effects of the content of graphene and MoS2 on the photocatalytic activity were investigated and the suitable preparation conditions were obtained. When the loading content of graphene was 7 wt% and that of MoS2 was 2 wt%, the BiPO4/graphene/MoS2 nanocomposite exhibited the most effective photocatalytic activity under the irradiation of a 300 W high-pressure mercury lamp, which was much better than that of BiPO4 alone. This is because the synergistic effect of cocatalyst promoted the transportation and transfer of electronic.(3)TiO2–Bi2WO6 heterostructure microspheres were successfully fabricated using glucose as template by means of one-pot hydrothermal method followed by calcination at 450 oC. The photodegradation experiments for the degradation of Rhodradation B under visible light irradiation indicated that the TiO2-Bi2WO6 composites exhibited higher photocatalytic activity than those of either individual TiO2 and Bi2WO6, which could be attributed to the high separation of photogenerated electron–hole pairs resulted by the Ti O2-Bi2WO6 heterojunctions. Moreover, the photocatalytic mechanism was investigated by active species trapping experiments, indicating that photogenerated holes should be the main active species in RhB photodegradation.