掺杂改性TiO₂光催化剂的制备及其活性研究

【作者】 孙柳；

【导师】 文晨；

【作者基本信息】 天津工业大学 ， 环境工程， 2006， 硕士

【摘要】 TiO₂光催化氧化技术作为一种新的污染治理技术，因其具有能耗低、反应条件温和、操作简便、无二次污染等优点而倍受关注。然而，因TiO₂是宽禁带半导体（Eg^～3.2eV），只有在能量较高的紫外光照射下才表现出光催化活性，而太阳光中的可见光不能有效利用，同时光生电子与空穴的复合几率高，量子产率低，故上述诸缺陷极大地限制了该技术在实际中的广泛应用。针对TiO₂光催化氧化技术存在的缺陷，提出了离子掺杂改性TiO₂光催化剂的设想。本论文采用溶胶-凝胶法分别制备了稀土（Ce）、非金属（I和F）掺杂的TiO₂光催化剂，通过改变掺杂元素、掺杂量和焙烧温度等考察对TiO₂光催化活性的影响，同时借助XRD、TEM、XPS、UV-Vis等分析手段，表征了改性TiO₂微观结构。此外，以亚甲基蓝染料为目标污染物，探讨了在模拟太阳光照射下该改性TiO₂的光催化活性，并对其再利用性进行了初步探讨。研究表明，Ce、I及I／F的掺杂不仅可以阻碍TiO₂光催化剂由锐钛矿相向金红石相的转变，提高其热稳定性，而且还抑制了TiO₂晶粒生长，提高了比表面积。三种改性TiO₂光催化剂在紫外光区的吸光性增强，且发生微少蓝移，同时在400-600 nm可见光区的吸光性也有所增强。由光催化降解亚甲基蓝（10mg／L）的实验结果表明：Ce／Ti摩尔比为0.05％，500℃下焙烧2h的TiO₂光催化活性最佳，光照4h亚甲基蓝的降解率达到73％；当I／Ti摩尔比为10％，500℃焙烧2h的TiO₂光催化活性最高，光照4h亚甲基蓝的降解率接近约82.3％：500℃焙烧2h的I／F共掺杂TiO₂催化活性也显著地提高，在光照2h亚甲基蓝的降解率达97.4％。经离子色谱分析，亚甲基蓝溶液完全脱色后可逐渐生成NH₄⁺，NO₃^-和SO₄^2-等无机离子。更多还原

【Abstract】 The photocatalytic oxidation technique of TiO₂ has been paid more and more attention for many advantages, such as less energy cost, mild reaction condition, easy operation and less secondary pollution. However, TiO₂ may show photocatalytic activity only under irradiation of ultraviolet （UV） light for its wide band gap （Eg³.2eV）, most of the sun light is underutilized. Furthermore, easy recombination of photo-induced electrons and holes makes the efficiency of photoquantum low. Those unfavorable factors have the photocatalytic oxidation technique of TiO₂ limited in practice.Considering the problems above, the idea of TiO₂ photocatalysts by doping modification was presented. Pure TiO₂, Ce-doped, I-doped and I/F codoped TiO₂ photocatalysts were prepared by sol-gel method. The microstructures of prepared photocatalysts were characterized by XRD, TEM, XPS and UV-Vis analysis. The effect of calcining temperature and content of dopants on the photocatalytic activity was studied by decomposing methylene blue. Recycle of photocatalysts was also discussed in this paper.The study showed that the doping modification not only prevented the phase transformation process of Ce-doped, I-doped and I/F codoped TiO₂ photocatalysts from anatase to rutile, but also suppressed crystal growing. Compared to pure TiO₂, those three TiO₂ photocatalysts revealed stronger absorption and blue shift in the UV light region, and the responding area to sunlight was enlarged to visible light area.The results of photocatalytic degradation for methylene blue（10mg/L） indicated that photocatalytic activity of 0.05%Ce-TiO₂ and 10%I-TiO₂ calcined at 500℃ was the highest among the Ce-TiO₂ and I-TiO₂. The photodegration rate reached 73% and 82.3% in 4h, respectively. Photocatalytic activity of I/F-TiO₂ also improved obviously, 97.4% of methylene blue was photodegraded after 2h of irradiation. Besides, it was found that methylene blue mineralized eventually into NH₄⁺, NO₃^- and SO₄^2-, respectively.更多还原