Preparation And Modification Of Tetratitanate For Efficient Photocatalysis

The human society is facing increasingly serious energy shortages and environmental pollution problems. In order to solve these problems, people pay more and more extensive attentions to photocatalytic technology and semiconductor photocatalysts. In fact,semiconductor photocatalyst has been proven to be a kind of idea green catalyst for its high photocatalytic efficiency and low cost. However, its application is limited by the shortage of poor solar energy utilization and low quantum efficiency. As one of these photocatalysts which have high photocatalytic activities, K₂Ti₄O₉ has unique layered structure which can be used as tempting parent material to fabricate other composite catalyst. In this work, precursor potassium tetratitanate?K₂Ti₄O₉? was prepared by solid-phase reaction, and a series of composited photocatalysts were designed and synthesized.?1? K₂Ti₄O₉ with layered structure was synthesized by a solid-phase reaction using K2CO3 and TiO₂ as raw materials, then the product was washed by different processes. The effect of excess salt on the catalytic performance of K₂Ti₄O₉ was studied. The results demonstrated that the energy gap of K₂Ti₄O₉ is evidently narrowed with the increase of solvent washing time, and red shift of optical absorption band edge was observed.Photocatalytic degradation of methylene blue was investigated under ultraviolet light. The degradation efficiency of methylene blue for K₂Ti₄O₉ washed for three times is more than twice higher than that of the unwashed ones. And it also shows better efficiency for photoelectric chemical decomposition of water than that of the unwashed ones.?2? Protonic layered tetratitanate?H2Ti4O9? was obtained by subsequent acidification of K₂Ti₄O₉ with different acid solutions including hydrochlric,phemethylol and ethanol. The obtained catalyst was named as K₂Ti₄O₉-acid,K₂Ti₄O₉-BA and K₂Ti₄O₉-EtOH, respectively.The impression of proton exchange methods on the structure and the photocatalytic performance of the product was investigated in this work. The results demonstrated that the ultraviolet light absorption of K₂Ti₄O₉-BA and K₂Ti₄O₉-Et OH was much stronger than the K₂Ti₄O₉-acid catalyst. The recombination of photo-induced electron-hole pairs in the K₂Ti₄O₉-BA and K₂Ti₄O₉-EtOH reduced a lot as compared with K₂Ti₄O₉-acid, Photolysis aquatic hydrogen rate of K₂Ti₄O₉-EtOH was 23.4% higher than the K₂Ti₄O₉-acid catalyst under sunlight illumination.?3? H2Ti4O9 was calcined at different temperature to further evaluate the effect of temperature on the crystal form and the photocatalytic performance of TiO₂. Result shows that TiO₂?B? with monoclinic crystal was detected when the calcining temperature was about350 ?, but it converted to anatase TiO₂ gradually with the increase of calcining temperature.When the calcination temperature was up to 750 ?, anatase TiO₂ became the main crystal,while TiO₂?B? was detected barely at the same time. The crystalline of TiO₂ increased with the raise of calcining temperature, as well as the enhancement of the the photocatalytic performance,correspondingly. In this work, the degradation efficiency of methylene blue for TiO₂-750 ? was 88.7% higher than the TiO₂-350 ?.?4? A novel heterojunction catalyst?K₂Ti₄O₉-TiO₂? was fabricated via hydrolysis,solvent evaporation and high-temperature calcination processes using K₂Ti₄O₉ and tetrabutyl titanate?TBOT? as raw materials. Results show that the energy gap of K₂Ti₄O₉-TiO₂ was slightly narrowed with the increase of TBOT. and red shift of optical absorption band edge was observed compared with the unmodified K₂Ti₄O₉. The degradation efficiency of methylene blue for K₂Ti₄O₉-TiO₂ heterojunction catalyst was 73% higher than unmodified K₂Ti₄O₉. And the heterojunction catalyst has most photocatalytic activity when 1ml tetrabutyl titanate?TBOT? was added.