Synthesis,Characterization And Property Research Of Novel Bismuth Semiconductor Photocatalysts

With the rapid development of economics and science technology,environmental pollution and energy crisis have a serious impact on the daily life of human,developing new energy has become a hot research field covering function materials and environmental sciences.Photocatalytic technology provides a green method to solve environmental pollution and energy crisis.Photocatalytic material is the key of the photocatalytic technology.The band structure of photocatalytic materials is composed of a valence band with full electronic and an empty conduction band,when it is radiated by light whose energy is not less than the band gap of the materials.The electrons in the valence band can be excited to the conduction band,forming the electron-hole pairs.Then the electron-hole pairs react with the H2O,OH-and O2 that are adsorbed on the catalyst to produce reactive oxygen species(·O2-、H2O·、H2O2,·OH、·O2-、H2O·or H2O2),the oxidizability of reactive oxygen species is so strong that they can degradate pollutants,purify the environment.The compounds formed by bismuth and other elements not only possess a variety of crystal structure and electronic structure,but also show strong photocatalytic properties,and some compounds show better photocatalytic performance in the visible region.However,they still have some shortcomings,such as a low separation efficiency of photo-generated electrons and holes and the small surface area,which has a biggish limitation to their application.Doping metal ions can produce lattice defects or level defects in the semiconductor,which is due to the change of excitation wavelength of the semiconductor and the increase of diffusion length of carriers,thereby suppressing recombination of electrons and holes and enhancing the photocatalytic activity of semiconductor.The research contents are as follows:(1)BiNbO4 samples doped with La and Zn were prepared by chemical coprecipitation,and the samples were characterized by means of modern testing techniques,which proved that La and Zn had been successfully dopped into the BiNbO4.The influence of the dosage of the photocatalyst,the content of the dopant,the concentration and pH of RhB solution,and light source on performance of photocatalytic were studied by regarding Rhodamine B as simulated organic pollutant.The results showed that the photocatalytic activity of Bi1-xLaxNbO4 and Bi1-xZnxNbO4 on RhB were better than BiNbO4.The photocatalytic effect of Bi0.96La0.04NbO4 was the best in visible light when the concentration and pH were respectively 5 mg·L-1 and 4 of RhB solution,and the dosage of the photocatalyst was 0.15 g.And it had good performance for repeated use in the same experimental conditions.(2)BiVO4 samples doped with La and Zn was prepared by hydrothermal method,and the samples were characterized by means of modern testing techniques,which proves that La and Zn had been successfully doped into the BiVO4.The influence of the dosage of photocatalyst,the content of dopant,the concentration and pH of RhB solution,and light source on performance of photocatalytic were studied by regarding RhB as simulated organic pollutant.The results showed that the photocatalytic activity of Bi1-xLaxVO4(EDTA)and Bi1-xZnxVO4(EDTA)on RhB solution were better than BiVO4.The photocatalytic activity of Bi0.92Zn0.08VO4(EDTA)was the best in visible light when the concentration of and pH were respectively were 5 mg·L-1 and 4 of RhB solution and the dosage of the photocatalyst was 0.1 g.And it had good performance for repeated use in the same experimental conditions.(3)Taking the above samples as antibacterial agents,the antibacterial properties of the samples were studied agaist Escherichia coli,Staphylococcus aureus and Candida albicans.The experiments indicated that the antibacterial activity of Bi0.96La0.04NbO4 and Bi0.92Zn0.08VO4(EDTA)agaist three kinds of strains are best in the homology,and the antibacterial effects of each nanoparticle were the best against Candida albicans.(4)The photocatalytic degradation mechanisms of samples on RhB were studied.The experimental results showed that ·OH was the main active substances.That is to say,photo-generated electron-hole pairs in the catalyst produced by the light irradiation played an important role.Similarly,the photo-generated electrons-hole pairs still played a leading role in photocatalytic antibacterial process.