多金属氧酸盐/TiO₂（WO₃）复合催化剂光解水催化性能研究

【作者】 兰文兰；

【导师】 李洁；

【作者基本信息】 中南大学 ， 物理化学， 2008， 硕士

【摘要】 设计和合成高效光催化剂是利用太阳能光催化分解水制氢的关键。本论文重点研究了二氧化钛和三氧化钨负载多金属氧酸盐(H₄SiW₁₂O₄₀和H₄PW₁₂O₄₀)及负载对多金属氧酸盐光催化活性的影响:采用溶胶-凝胶结合浸渍合成技术,制备了具有较高紫外光催化活性的负载型多金属氧酸盐纳米材料:H₄SiW₁₂O₄₀╱TiO₂、H₄PW₁₂O₄₀╱TiO₂,通过采用XRD、EDS、FT-IR、Raman、UV-DRS等手段对上述新材料进行了组成测定和结构表征,研究了在紫外光源照射下,POM/TiO₂复合催化材料光催化分解水的析氧率、反应机理。结果表明:母体POM基本骨架结构仍得以保留,POM/TiO₂在紫外范围内具有强烈的光吸收性能。当TiO₂为锐钛矿相、焙烧温度为250℃、焙烧时间为3h、质量比w（TiO₂）:w（POM）为1:10的POM/TiO₂光催化剂活性最高,H₄SiW₁₂O₄₀/TiO₂的最佳析氧率为269.94μmol·l^-1·h^-1,是H₄SiW₁₂O₄₀的1.4倍,TiO₂的4.5倍;H₄PW₁₂O₄₀╱TiO₂的最佳析氧率为199.95μmol·l^-1·h^-1,是H₄PW₁₂O₄₀的1.9倍,约为TiO₂的3倍。POM和TiO₂之间存在良好的协同效应。利用固相烧结和浸渍法相结合的技术合成了两种多金属氧酸盐/三氧化钨复合催化材料:H₄SiW₁₂O₄₀/WO₃和H₄PW₁₂O₄₀/WO₃,利用XRD、FT-IR、Raman、UV-DRS对制备所得产物进行了表征,并研究了该类新型复合催化剂在紫外光源照射下,光催化分解水析氧的催化性能。结果表明,在POM╱WO₃中,多金属氧酸盐的基本结构仍然完整,由于与载体WO₃之间存在着较强的吸附作用,致使POM/WO₃的谱线发生移动,峰强发生变化;焙烧时间、焙烧温度、质量比w（WO₃）:w（POM）和电子受体Fe³⁺的浓度等因素对POM/WO₃复合催化剂光催化分解水析氧的催化性能均有影响。电子受体Fe³⁺的浓度为5g╱L,质量比w（WO₃）:w(H₄SiW₁₂O₄₀)为1:10的H₄SiW₁₂O₄₀╱WO₃复合催化剂在400℃下焙烧3h时光催化活性最佳,析氧率为143.13μmol·l^-1·h^-1,但仍然没有H₄SiW₁₂O₄₀的析氧率高;电子受体Fe³⁺的浓度为5g╱L,质量比w（WO₃）/w(H₄PW₁₂O₄₀)为1:5的H₄PW₁₂O₄₀╱WO₃复合催化剂在400℃下焙烧3h时光催化活性最佳,析氧率为114.50μmol·l^-1·h^-1,略高于H₄PW₁₂O₄₀的析氧率。更多还原

【Abstract】 Design and synthesis of high efficient photocatalyst is significant for solar hydrogen.This research focuses on preparation and characterization of polyoxometallate supported TiO₂ or WO₃ photocatysts for water splitting.Some innovative results are as follows:Polyoxometallate supported catalysts such as H₄SiW₁₂O₄₀/TiO₂、H₄PW₁₂O₄₀/TiO₂,with a high activity under ultraviolet radiation were prepared by sol-gel technology and impregnation methods.Samples were characterized by XRD,EDS,FT-IR,Raman and UV-DRS.Oxygen production rate and reaction mechanism of POM/TiO₂ composite catalysts were investigated.The results indicate that original structure of POM was retained and POM/TiO₂ showed a strong capacity in absorbing ultraviolet.Moreover,as titanium dioxide was in anatase phase,the calcination temperature and time was 250℃and 3h respectively,the mass ratio of TiO₂ to POM was 1:10,the photocatalytic activity reached the top, the fastest oxygen production rate of H₄SiW₁₂O₄₀/TiO₂ was 269.94μmol·l^-1·h^-1,which was 1.4 times to that of H₄SiW₁₂O₄₀,and 4.5 times TiO₂,which showed synergetic effect existed between POM and TiO₂.Two kinds of POM/WO₃ composite catalysts,H₄SiW₁₂O₄₀/WO₃ and H₄PW₁₂O₄₀/WO₃ were prepared by solid-state sintering method and impregnation.XRD,FT-IR,Raman,UV-DRS were applied to characterize their structure and their photocatalytic performance in oxygen production for water splitting under ultraviolet.The result showed that catalysts were in nano size.For POM/WO₃,original structure of POM didn’t change significantly.Because of the physical interaction between WO₃ and POM,IR spectra peak intensity of POM/WO₃ changed. Calcination time,temperature,mass ratio（w（WO₃）:w（POM））and concentration of Fe³⁺would affect performance of catalysts.As concentration of electron acceptors was 5g/L,and when the ratio(w （WO₃）:w(H₄SiW₁₂O₄₀))was 1:10,calcination time and temperature was 3h and 400℃respectively,H₄SiW₁₂O₄₀/WO₃ composite catalyst exhibited the highest photocatalytic activity,and oxygen production rate was 143.13μmol·l^-1·h^-1,however,this value was still lower than that of H₄SiW₁₂O₄₀;when concentration of Fe³⁺was 5g/L,mass ratio(w（WO₃） /w(H₄PW₁₂O₄₀))was 1:5,calcined for 3h under 400℃,the catalyst showed the best performance and oxygen production rate was 114.50μmol·l^-1·h^-1,slightly higher than that of H₄PW₁₂O₄₀.更多还原