Preparation Of Bi-based Semiconductor Catalysts And Performance For Degradation Of Environmental Pollutants

This thesis mainly contains two important parts.One is BixOyFz photocatalysts with different F/O ratios and investigated as their photocatalytic activities for the degradation of RhB under UV light irradiation;the second part is to reveal the correlation of photocatalytic activity with crystal structure for degrading RhB under visible and UV light irradiation.?1?BixOyFz was successfully prepared by a simple hydrothermal method without using any surfactant or template.The samples were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,UV-vis diffuse reflectance spectra?UV-DRS?,Photoluminescence?PL?spectra and N2 sorption isotherms.It is found that with the decrease of F/O ratio,the photocatalytic activities increase gradually,suggesting that the intensity of IEF may increase with the decrease of F.Under UV light irradiation,the apparent reaction kinetic rate constant of BiOF?F/O = 1?is 2:08 and 2.21 times higher than that of Bi7O5Fii?F/O = 2.2?and BiO0.9F2.35?F/O = 2.6?.respectively.?2?To the best of our knowledge,the differences of crystal structure between Bi₂SiO₅ and Bii2SiO20and the correlation of photocatalytic activity with crystal structure still remains unclear.Herein,the Bi₂SiO₅ and Bi12SiO20 have been prepared through a mild post-synthesis method.The samples were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,UV-vis diffuse reflectance spectra?UV-DRS?,Photoluminescence?PL?spectra,Surface photovoltage spectra?SPY?and N2 sorption isotherms.Bi₂SiO₅ shows a higher photocatalytic activity than Bii2SiO20 for the degradation of RhB.The apparent reaction kinetic rate constant of Bi₂SiO₅ is 2.1 times higher than that of Bi12SiO20.On base of the results above,the high UV light photoactivity of Bi₂SiO₅ can be understood as follows.First,the significantly higher BET area?Bi12SiO20 1.6 m2g-1,Bi₂SiO₅ 28.3 m2g-1?;Second,a layer structure is beneficial for the charge separation and transfer;in addition,the featured Bi-O-Si bonds of Bi₂SiO₅,acting as a passageway,could favor for the electron transfer in the bulk.