| Nano-TiO2 has been widely studied and used in many fields,such as energy utilization and environmental purification because of its abundant reserves,low cost,stable chemical properties,photocatalytic oxidation ability,non-toxic,and good environmental compatibility.However,there are still some problems such as low solar energy utilization and low quantum efficiency in practical applications,which greatly limit its application prospect.Gaseous detonation method,as a new preparation method,has many advantages,such as fast reaction rate,high yield,high purity and simple operation process.In this paper,Ti02 and Ti02-based composites photocatalysts were prepared by the gaseous detonation method.First,the effects of detonation parameters and preparation conditions on the phase,morphology and photocatalytic activity of TiO2 have been studied.The samples with highest photocatalytic activity have been obtained.Second,in order to improve the photocatalytic activity of TiO2,S/TiO2(S=SnO2,SiO2,Fe2O3)was prepared,and the effects of different S contents on the phase,morphology and photocatalytic activity of the composite samples were investigated also.The main researching results are as follows:Based on the theory of gas detonation,the effects of detonation velocity and explosion temperature on the morphology and structure of TiO2 were investigated.The nucleation and growth mechanism of TiO2 in gas phase detonation reaction was analyzed.The growth process of TiO2 particles was simulated by particle growth model.The results were agreed well with the experimental results.1.The effect of preparation conditions on the photocatalytic activity of Ti02 was studied by an orthogonal design method and the sample with the highest photocatalytic activity was obtained.The results show that the amount of TiCl4 has a significant influence on the photocatalytic activity and has a certain influence on the average particle sizes of the product.The particle size of the sample is small,and high photocatalytic activity is observed.Furthermore,the anatase phase structure has higher photocatalytic activity than that of the rutile phase.The initial temperature was 130 C,TiCl4:H2 was 1:2 and the amount of TiC1U was 2ml.The samples with the highest photocatalytic activity could be prepared.The average particle size was approximately 20nm,and the crystal structure was anatase-rutile mixed crystal,with the anatase phase content of 78.2%,band gap width of 3.18eV,and the apparent reaction rate constant k of 0.0997.The photocatalytic activity of them was close to the commercial P25.Sn02-TiO2 composites were prepared by the gaseous detonation method.The effects of different Sn/Ti molar ratios on the morphology and photocatalytic activity of the products were studied.The results show that SnO2 and TiO2 rutile phase form a solid solution,which can promote the formation of rutile phase,inhibit the growth of TiO2 particles and increase the specific surface area and the band gap;Moreover,after the formation of heterojunction composite,it can reduce the combination of electrons and holes,and improve the photocatalysis of the samples.As SnO2 content increased,photocatalytic activity of the samples presented firstly rising and then descending trend,but was higher than that of pure TiO2.Samples with Sn/Ti = 1/4 achieved the highest photocatalytic activity.The average particle size was about 19 nm.The content of the rutile phase was 49%,the specific surface area is 86m2/g,the forbidden band width was 3.26eV,the apparent reaction rate constant k was 0.163 min-1,and the photocatalytic activity was higher than P25.SiO2-TiO2 composites were prepared by the gaseous detonation method.The influences of different SiO2 contents on the morphology and photocatalytic of the samples were studied.The results show that the Ti-O-Si structure is formed after the surface vacancy of the TiO2 is filled with Si atoms.The surface of the protective layer and the existence of this structure inhibited the growth of TiO2 particles and transformation of anatase to rutile phase,increasing the specific surface area of the sample.The presence of excess SiO2 allows the amorphous SiO2 to coat the Ti02 particles,hindering the contact of the TiO2 surface with the methyl orange solution,adversely affecting the photocatalytic activity.As SiO2 content increased,photocatalytic activity of the samples presented firstly raised and then descended;when SiO2 content was 5mol%,the samples were of anatase-phase structure,with the average particle size of 15.3nm,specific surface area of 77m2/g,presented optimal photocatalytic activity,and apparent reaction rate constant of k=0.112min-1 which was higher than the pure TiO2.Fe2O3-TiO2 composites were prepared by the gaseous detonation method.The effects of different Fe3+ on the morphology and photocatalytic of the samples were studied.The results show that Fe3+ can promote the formation of rutile phase and increase of particle size and agglomeration of TiO2 particles.The combination of Fe2O3 and TiO2 can effectively reduce the sample bandwidth and improve the absorbance in the visible region.When the Fe/Ti molar ratio was 1%,the sample achieved the highest photocatalytic activity.The average particle size was about 20 nm,the content of rutile phase was 23.7%,the forbidden band width was 3.1eV,the apparent reaction rate constant k is 0.142min-1 and the photocatalytic activity was higher than P25. |
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