【作者】 卢智宇；

【导师】 姜洪泉；

【作者基本信息】 哈尔滨师范大学 ， 无机化学， 2011， 硕士

【摘要】 本文以提高纳米TiO₂的太阳能利用率、抑制光生电子和空穴复合、提高量子化效率为目的,开发出高性能的TiO₂纳米复合光催化剂,为利用光催化技术治理环境污染提供了新型光催化材料。利用溶胶-凝胶法制备Tm掺杂TiO₂纳米复合光催化剂,采用XRD、DRS和PL技术研究了Tm掺杂量和焙烧温度对样品的相结构、晶粒尺寸、光吸收及光致发光性能的影响;以亚甲基蓝（MB）溶液的光催化降解评价其紫外光活性。结果表明:低量Tm掺杂强烈抑制TiO₂由锐钛矿相向金红石相转变,但随Tm掺杂量增加,抑制相变作用减弱。Tm掺杂导致样品的紫外吸收能力略有降低,光吸收带边蓝移。Tm掺杂样品的PL谱强度降低与其紫外光活性升高顺序并不完全一致。当Tm掺杂量为0.075wt%,焙烧温度为550℃时,制得的Tm掺杂TiO₂纳米复合光催化剂呈双相结构,锐钛矿相占91%,晶粒尺寸为24.48 nm,其紫外光活性最佳。紫外光活性提高的主要根源是Tm掺杂能有效促进TiO₂纳米光催化剂表面光生e-/h+的分离,提高量子化效率。在此基础上,采用溶胶-水热法系统开展Tm、N单掺杂及共掺杂TiO₂纳米复合光催化剂的制备工艺研究,利用XRD、BET、XPS、FT-IR、DRS及PL技术对其进行了结构性能表征,探讨了Tm和N掺杂对TiO₂光活性的影响机制。结果表明:当Tm掺杂量为0.075%,焙烧温度为550℃时,制得的Tm掺杂样品紫外光活性为63.19%,比光活性为5.92×10^-5 mol·g^-1·h^-1,是溶胶-凝胶法制备的Tm掺杂样品(比光活性为8.64×10^-6 mol·g^-1·h^-1)的6.85倍。当氨水添加量为2 mL,焙烧温度为440℃时,制得的N掺杂样品可见光活性为62.63%,比光活性为5.87×10^-5 mol·g^-1·h^-1,是溶胶-凝胶法制备的N掺杂样品(比光活性为6.59×10^-6 mol·g^-1·h^-1)的8.91倍。显然,采用溶胶-水热法制得的样品微观织构特性好、结晶度高、粒径小,光活性高,说明溶胶-水热法明显优于溶胶-凝胶法。Tm掺杂导致样品光生e-/h+分离效率提高,有效抑制相变,提高晶化程度,均有利于其紫外光活性的提高。N掺杂样品呈现优异的可见光活性。N掺杂导致样品吸收带边红移,拓宽光响应范围至可见光区,产生大量表面态及缺陷、增加表面羟基含量,有利于可见光活性的提高。Tm、N共掺杂样品的可见光活性介于TiO₂样品及N掺杂样品的可见光活性之间,紫外光活性低于TiO₂样品,表明Tm和N共掺杂并未产生协同作用。更多还原

【Abstract】 To improve the solar utilization ratio of nano-TiO₂, inhibit the recombination of photogenerated e-/h+ and enhance the quantum efficiency. TiO₂ nano-composite photocatalyts with high performance have been exploited, which could offer novel photocatalytic materials used in the treatment of environmental pollutants with photocatalytic technique.Tm-doped TiO₂ nano-composite photocatalysts with different doping contents or calcined at different temperatures were prepared by a sol-gel method. The effects of Tm-doping contents and calcination temperatures on their phase structures, crystallite sizes, light absorption performances and photoluminescence properties were investigated by the techniques such as XRD, DRS and PL. Their photocatalytic activities were evaluated by the photocatalytic degradation of methylene blue （MB） in aqueous solution. The results indicated that the presence of low amount Tm in TiO₂ could strongly inhibit the phase transformation from anatase to rutile. However, the effect of inhibition could gradually weaken with the increase of Tm-doping content. Tm-doping could result in both a slight decrease of their light absorption performance in ultraviolet region and a blue shift of their optical absorption edge. It can be verified that the decrease sequence of PL spectrum intensity for the samples doesn’t accord with the increase sequence of their photoactivity completely. Tm-doped sample with doping contents of 0.075wt% calcined at 550℃show the highest photocatalytic activity, which present two phase structure and include the anatase phase of 91%. Its crystallite size is 24.48 nm. The main origin of the higher UV photoactivity of the Tm-doped sample is that the separation of the photogenerated electron-hole pairs can be promoted by Tm-doping, leading to increasing quantum efficiency.On this basis, preparation process research of Tm-doped, N-doped and （Tm, N）-codoped TiO₂ nano-composite photocatalysts synthesized via a sol-hydrothermal method was systematically carried out. The structures and performance characterizations of prepared samples were investigated by the techniques such as XRD, BET, XPS, FT-IR, DRS and PL. In the meantime, the influencing mechanism of Tm and N doping on TiO₂ photoactivity was discussed. The results indicated that Tm-doped sample with doping contents of 0.075wt% calcined at 550℃showed excellent UV photoactivity. Its UV photoactivity is 63.19%, its specific photoactivity is 5.92×10^-5 mol·g^-1·h^-1. Compared with Tm-doped sample (its specific photoactivity is 8.64×10^-6 mol·g^-1·h^-1) prepared by sol-gel, its specific photoactivity markedly improved 6.85 times. N-doped sample with ammonia water adding amount of 2 mL calcined at 440℃showed excellent visible light photocatalytic activity. Its visible light photoactivity is 62.63%, its specific photoactivity is 5.87×10^-5 mol·g^-1·h^-1. Compared with N-doped sample (its specific photoactivity is 6.59×10^-6 mol·g^-1·h^-1) prepared by sol-gel, its specific photoactivities markedly improved 8.91 times. Obviously, samples prepared by the sol-hydrothermal process could lead to excellent microstuctural properties, higher crystallinities, smaller grain sizes, higher photoactivies. These indicated that the sol-hydrothermal process were significantly better than sol-gel process. The Tm-doping can bring about higher photogenerated electron-hole separation efficiency, effectively inhibit the phase transformation, improve crystallinity degree. These factors facilitate its improvement of UV photoactivity. The N-doped sample exhibits outstanding visible light photoactivity. The N-doping can bring out its absorption edge red-shift, broaden light response range to visible light region, produce large numbers of surface states and defects, as well as increase the contents of surface hydroxyl groups, which result in the enhancement in visible light photoactivity. Visible light photoactivity of （Tm, N）-codoped sample was between that of TiO₂ and that of N-doped TiO₂, UV photoactivity lower than TiO₂, indicating no expectative synergetic effects produced from Tm and N codoping.更多还原