氧缺陷型TiO2-x可见光催化性能的研究

摘要

采用氢气还原法制备氧缺陷型二氧化钛(TiO2-x),考察氧气氛中不同返烧温度对TiO2-x性能的影响.利用X射线光电子能谱、电子自旋共振谱、紫外-可见漫反射光谱和荧光光谱等技术对样品的表面化学状态、氧缺陷位的种类、光吸收性能和光生载流子的分离效率等性质进行了表征,并以气相的苯为模型污染物,研究催化剂样品在可见光(λ＞400 nm)照射下的光催化氧化能力.结果表明,与未返烧的催化剂相比,返烧后TiO2-x对苯的光催化氧化降解能力显著提高,反应4h、催化剂活性稳定后,经300℃返烧的TiO2-x样品对苯的转化率为36.9％,是未返烧样品的5.3倍.还原过程中生成的体相氧缺陷位(束缚单电子的氧空位)是催化剂具有可见光催化性能的主要原因,返烧热处理减少了催化剂表面氧缺陷位(Ti3+)的浓度并有效地抑制了光生载流子的复合.%Oxygen-deficient titanium dioxide (TiO2-x) was prepared by heating TiO2 in H2 atmosphere, followed by the post-calcination in O2 at different temperatures. The physicochemical properties of the products were characterized by X-ray photoelectron spectroscope (XPS), electron spin resonance (ESR), UV-Vis diffuse reflectance spectrum (UV-Vis DRS) and photoluminescence spectrum (PL). The photocatalytic activity of the as-prepared samples was determined by the degradation of gas-phase benzene under visible light (λ > 400 nm) irradiation. The results show that the TiO2-x post-heated at 300 ℃ exhibits the highest photocatalytic activity. After photocatalytic oxidation for 4 h, the conversion rate of benzene over the catalyst is up to 36.9% at steady state, which is 5.3 times as much as that on the untreated sample. The enhanced photocatalytic performance of the TiO2-x is related to the amount of the oxygen vacancies in matrix (single-electron-trapped oxygen vacancies). The postcalcination successfully reduces the surface oxygen vacancies (Ti3+), efficiently hindering the photoinduced carriers from recombination.