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为提高TiO_2的光吸收和光催化能力,采用原位水热还原法将Au沉积到有序多孔TiO_2上,制备了有序大孔-介孔Au-TiO_2复合材料。材料的光催化活性以在紫外光和可见光辐射下降解罗丹明B来评价。漫反射吸收光谱显示Au-TiO_2复合材料在400~800nm有较强的吸收。在紫外光和可见光辐射下,Au-TiO_2复合材料的光催化活性优于TiO_2。在紫外光下Au-TiO_2-1.9是最高效的催化剂,3h内罗丹明B的降解率达84%,其表观速率常数K是TiO_2的2.8倍。这主要是因为沉积Au纳米粒子能有效促进电荷的分离,提高光催化效率,但过量的Au成为表面电子-空穴复合的中心,反而降低其光催化能力。在紫外光下,罗丹明B的降解反应属于准一级动力学反应,光生空穴是主要的活性物质。阻抗测试显示Au-TiO_2的圆弧半径小于TiO_2,表明电荷传递效率提高,有利于光生电子-空穴对的分离和光催化性能的提高。
In order to improve the light absorption and photocatalytic ability of TiO_2, Au was deposited on ordered porous TiO_2 by in situ hydrothermal reduction to prepare ordered macroporous-mesoporous Au-TiO_2 composites. The photocatalytic activity of the material was evaluated by degradation of rhodamine B under UV light and visible radiation. The diffuse reflectance absorption spectra show that the Au-TiO 2 composite has strong absorption at 400 ~ 800 nm. The photocatalytic activity of Au-TiO_2 composite is better than that of TiO_2 under ultraviolet and visible radiation. Under UV light, Au-TiO_2-1.9 is the most efficient catalyst. The degradation rate of Rhodamine B is 84% within 3h, and its apparent rate constant K is 2.8 times that of TiO_2. This is mainly because the deposition of Au nanoparticles can effectively promote the separation of charges and improve the photocatalytic efficiency, but excessive Au becomes the center of the surface electron-hole recombination, but decreases its photocatalytic activity. Under ultraviolet light, the degradation reaction of rhodamine B belongs to quasi-first-order kinetic reaction, and photogenerated holes are the main active substances. The impedance test shows that the radius of arc of Au-TiO_2 is smaller than that of TiO_2, indicating that the charge transfer efficiency is improved, which is conducive to the separation of photogenerated electron-hole pairs and the improvement of photocatalytic performance.