Preparation, Characterization Of Perovskite Structural K₂ La₂ Ti₃ O₁₀ And Its Photocatalytic Activity For Water Splitting Into Hydrogen

Semiconductor photocatalytic hydrogen production from water method is considered tobe the most promising method of photolysis of water into hydrogen for its simple, clean,economical and practical advantages. After over 30 years'development, the study ofphotocatalytic hydrogen production from water by utilizing solar energy has made greatprogress, but the low utilization of solar energy and rapid recombination between electronsand holes excited by irradiation are still the bottlenecks to restrict the high activity ofphotocatalytic materials. Based on these bottlenecks, the main research contents of this thesisis to develop perovskite structural K₂La₂Ti₃O₁₀ photocatalyst doped or codoped with differentions, and to study the relationship between the photocatlytic activities of hydrogen productionfrom water and the crystal structure, morphology, as well as the interaction of components onthe catalyst surface, bymeans of various characterization techniques.K₂La₂Ti₃O₁₀ photocatalyst samples were prepared by SSR, Sol-Gel and PC method, andcharacterized by TG, XRD, SEM, DRS; investigated the photocatytic activities for hydrogenevolution among the samples and compared the different preparation methodswhich effect onthe K₂La₂Ti₃O₁₀ hydrogen evolution activity. The results showed that K₂La₂Ti₃O₁₀ wasobtained using Sol - Gel method with single phase, uniform morphology and showed thehighest photocatalytic activity of hydrogen production from water. Compared with SSR andPC methods, the activities were 1.96 and 1.32 times to pure K₂La₂Ti₃O₁₀, respectively.A series of Fe, Cr doped K₂La₂Ti₃O₁₀ photocatalyst samples were prepared by Sol-Gelmethod. The structural and photoelectric properties of photocatalysts were characterized byXRD, DRS and XPS. The mechanism of photocatalytic hydrogen production of Fe, Cr dopedK₂La₂Ti₃O₁₀ was also discussed in the paper. The results showed the activities of K₂La₂Ti₃O₁₀doping Fe, Cr was significantly improved for Fe 3d, Cr 3d orbital and O 2p orbital werehybrided in K₂La₂Ti₃O₁₀ band gap and formed impure energy band on the top of VB,increased the absorption of light threshold. Meanwhile, the increase of oxygen vacancy onK₂La₂Ti₃O₁₀ surface reduced the recombined probability between electrons and holes in thecompound. When the ratio of Fe/Ti and Cr/Ti are 0.03 and 0.01-0.02, respectively, thesamples were the highest photocatalytic activity for hydrogen evolution, the hydrogen production rates were 62.25μmol·h^-1 and 47.59μmol·h^-1, which were 3.70 and 2.71 timeshigher than the pure ones.Aseries of B, Cr co-doped K₂La₂Ti₃O₁₀ photocatalyst samples were prepared by Sol-Gelmethod and characterized by XRD, DRS and XPS. The results showed B, Cr co-dopedK₂La₂Ti₃O₁₀ expanded the range of visible light response. Meanwhile, B, Cr co-dopedK₂La₂Ti₃O₁₀ significantly increased the surface oxygen vacancy content, and further to inhibitthe recombination between electrons and holes, which greatly improved the photocatalyticactibity for hydrogen evolution. When the ratio of B: Cr: Ti was 0.02: 0.01: 1, its highestphotocatalytic activity of hydrogen evolution rate reached 79.16μmol/h, which was 1.62 times and 4.79 times to Cr doped and pure K₂La₂Ti₃O₁₀, respectively.