Modification Of BIPO₄ For Efficient Photodegration Of Organic Pollutants

The development of human beings brings convenience to the human life, while it brings more and more problems. In recent years, the issue of environmental pollution especially water pollution has become more and more serious. For the sake of posterity,environmental protection is particularly important. Compared with the traditional method of biodegradation and physical adsorption, because of its environmentally friendly, no secondary pollution, thorough treatment and degradation of organic pollutants under the excitation of photo etc., novel photocatalytic technology has been drawing more and more attention because of its environmental benignity, no secondary pollution, thorough degradation of organic pollutants under the excitation of photons etc. Thus more and more semiconductor materials have been discovered. BiPO₄, as a novel photocatalyst,was firstly published by Yongfa Zhu’s group in 2010. The band gap of BiPO₄ is between 3.8-4.2eV, which has good photocatalytic activity for the degradation of organic pollutants under UV light.It well known that the properties of semiconductor photocatalysts are closely related to the band gap, the conductivity and the ability for separation of photogenerated charge separation. At present, the methods to improve the separation efficiency of semiconductor materials are semiconductor composition, noble metal deposition, doping of metal and nonmetal ions and so on, In order to improve the photocatalytic activity of BiPO₄, BiPO₄ has been modified for organic pollutant degradation based on the facilitation of the separation efficiency of photogenerated charge. The main contents of this thesis are as follows:1.Core-shell structure g-C₃N₄/BiPO₄ composites have been prepared by one-step hydrothermal for organic pollutant degradation. g-C₃N₄ nanosheets were synthesized on the basis of a direct thermal oxidation "etching" process for bulk g-C₃N₄ reported previously. A series of g-C₃N₄/BiPO₄ composites were prepared with different mass of g-C₃N₄ nanosheets. The physicochemical properties of as-prepared g-C₃N₄/BiPO₄ composites were investigated by XRD, SEM, TEM, XPS, BET, DRS, etc. It is found that the g-C₃N₄/BiPO₄ composites exhibited much higher photocatalytic activity for the degradation of MB and DMP than bare BiPO₄ and commercial TiO2 product（P25） under UV light. That the reason may be due to that traditional heterojunction structure may be formed inside the g-C₃N₄/BiPO₄ composite formed the traditional heterojunction structure, which improved the separation ability of the photogenerated charge of BiPO₄,and therefore enhanced the photocatalytic degradation effect efficiency.2. Au/BiPO₄ composites were prepared by photodeposition of Au nanoparticles onto the surface of BiPO₄. A series of Au/BiPO₄ composites were synthesized with different amount of chloroauric acid. The atomic ratio of Au in prepared samples was measured by EDX. The physicochemical properties of as-prepared Au/BiPO₄ composites were investigated by XRD , SEM, TEM etc. The composites exhibited much high photocatalytic activity for MB degradation than bare BiPO₄ and P25 under UV light. The size of Au nanoparticles was about 5nm. Due to the presence of Au particles, there are lots of electron traps on the surface of BiPO₄, which changes the transfer route of photoinduced electron and leads to the effective separation of photogenerated electrons and holes for the improvement of the photocatalytic performance.