二氧化钛/溴化银-银/导电聚合物纳米复合材料的制备及可见光催化机理的研究

TiO2, as an excellent photocatalyst, has been widely used in many application fields such as the decomposition of the organic contaminants in air and water. However, the low visible light photocatalytic activity doesn't favor its application in more fields. In this study, the TiO2/AgBr-Ag/conducting polymer nanocomposites will be prepared by the methods of sol-gel, in-situ deposition reaction and in-situ polymerization. The visible light response of TiO2 can be improved by the sensitization of AgBr while both the reduced probability of Ag+ by the photogenerated electrons in the nanocompostes and the recombination probability between the electrons and holes photogenerated in the nanocomposites can be decreased by the electron conducting property of the investigated conducting polymers. Therefore, the visible light photocatalyst TiO2/AgBr-Ag/conducting polymer with high photocatalytic activity and stability can be prepared by compounding TiO2, AgBr, Ag and conducting polymer. The visible light photocatalytic activity and stability of these nanocomposites will be investigated by evaluating the decomposition of the model organic contaminants such as methyl orange and phenol. The relationship among their chemical composition, micro-structure and visible light photocatalytic activity will be investigated and their visible light photocatalytic mechanism will be clarified systematically. The investigated visible light photocatalytic mechanism mainly includes the formation process of the photogenerated electrons and holes, the transmission mechanism of the electrons in the nanocomposites, the formation mechanism of the photocatalytic active-species, and the degradation mechanism of the organic contaminants photocatalyzed by the nanocomposites under the visible light irradiation. The above investigating results can play an important role in the preparation of highly efficient visible light photocatalyst and in the highly efficient degradation of the organic contaminants in air and water.

TiO2是一种性能优异的光催化剂，在催化降解大气及水体有机污染物方面表现出了较好的应用前景，但较弱的可见光催化活性限制了其广泛应用。本研究拟采用溶胶凝胶法、原位沉淀法和原位聚合法制备TiO2/AgBr-Ag/导电聚合物纳米复合材料，利用AgBr的光敏性提高TiO2的可见光响应性，利用导电聚合物的电子输运性有效降低复合材料内光生电子还原银离子的几率和光生电子/空穴的复合几率，得到高效稳定的TiO2/AgBr-Ag/导电聚合物可见光催化剂。以甲基橙、苯酚等为模型有机污染物，考察该纳米复合材料可见光催化活性及稳定性，建立其组成-结构-可见光催化活性间的内在关系，揭示其在可见光下光生电子/空穴的生成历程及电子在复合材料内部的传导机制、催化活性中心的种类及生成机理、有机污染物可见光催化降解的反应历程，为高性能可见光催化剂的研制和有机污染物的高效降解提供理论依据。

以钛酸四丁酯为主要原料，采用溶胶-凝胶法制备TiO2凝胶，将TiO2凝胶置于温度≤90℃的水浴中或温度≤300℃的空气中处理，制备具有介孔结构和可见光催化活性的锐钛矿型TiO2纳米微粒。该类纳米微粒的晶粒尺寸5-10 nm，比表面积200-300 m2∙g–1，禁带宽度2.79-3.14 eV，具有良好的可见光催化活性和稳定性；其紫外光和可见光催化活性均高于商品TiO2P25。.以钛酸四丁酯、CTAB等为主要原料制备含有CTAB的TiO2凝胶；将该TiO2凝胶浸渍到AgNO3溶液中，通过原位沉淀反应制备含有AgBr纳米微粒的 TiO2凝胶。将该TiO2凝胶进行可见光辐照，使部分AgBr分解生成Ag，制备同时含有AgBr和Ag纳米微粒的 TiO2凝胶。煅烧该凝胶，得到具有介孔结构的AgBr-Ag/TiO2纳米复合材料。该纳米复合材料由TiO2、AgBr和Ag纳米微粒组成，晶粒尺寸分别为14.3、8.0和1.9 nm，比表面积约为200 m2•g -1。AgBr-Ag/TiO2纳米复合材料表现出优异的可见光催化活性和稳定性，其可见光催化活性分别为商品TiO2P25和AgBr-Ag/SiO2的36.1和2.7倍。.采用苯胺、吡咯、噻吩及其衍生物的原位聚合反应或者聚氯乙烯、聚丙烯腈等聚合物的化学反应，在商品TiO2纳米微粒或自制TiO2纳米微粒表面生成导电聚合物层，制备TiO2/导电聚合物纳米复合材料。向TiO2表面引入少量的导电聚合物不改变TiO2纳米微粒的晶型结构和微粒尺寸，但显著提高其可见光吸收能力，减小其荧光光谱强度，提高其可见光催化活性。另外，TiO2/导电聚合物纳米复合材料具有较好的可见光催化稳定性，其可见光催化活性主要来自于导电聚合物的光生电子。.以介孔AgBr-Ag/TiO2纳米复合材料为原料，采用苯胺、吡咯等原位聚合反应或聚氯乙烯、聚丙烯腈等化学反应，制备AgBr-Ag/TiO2/导电聚合物纳米复合材料。少量的导电聚合物引入到介孔AgBr-Ag/TiO2纳米复合材料后，其晶型结构、晶粒（AgBr、Ag和TiO2纳米微粒）尺寸和介孔结构没有明显变化，但其可见光吸收能力显著提高，光生电子/空穴的复合几率明显减小，可见光催化活性和稳定性大幅度提高。该类纳米复合材料的可见光催化活性主要来自于AgBr的光生空穴和导电聚合物/AgBr的光生电子。