掺镧多孔TiO2纳米晶表面电子结构与能量转换机制

采用溶胶-凝胶法制备多孔掺镧纳米晶二氧化钛样品. 结合光声与表面光伏技术, 研究样品的光声和表面光伏特性. 分析认为, 掺镧后在表面上富集的La-O-Ti化合物形成的施主态活性中心吸附氧和H2O分子后生成的活性氧和羟基, 导致了吸附表面光激发电荷转移跃迁的催化光反应(sensitized photoreaction)机制. 实验证实, 适当的镧掺杂不仅可以增强样品的表面光伏特性, 而且可以有效地抑制非辐射跃迁的发生, 提高光量子效率. 实验在指认与样品非辐射退激有关的电荷转移跃迁过程的同时, 证实非辐射跃迁过程与样品表面是否生成活性氧和羟基活性中心无关.

Electron Structure and Energy Transformation Mechanism of the Surface of Porous Nanocrystalline TiO2 Doped with La

The porous nanocrystalline TiO2 doped with La was synthesized by sol-gel method. The combination of the photoacoustic (PA) and the surface photovoltage (SPV) techniques was proved to be a promising experimental method to probe the photogenic electron behaviors and electron structure on the surface. Results showed that active oxygen and hydroxy were formed on the donor-type active centers produced by the La-O-Ti compounds enriched on the surfaces, which resulted in the sensitized photoreaction of charge transfer transitions on the surface after adsorbing oxygen and H2O. It was experimentally confirmed that doping an appropriate amount of La not only enhanced the surface photovoltage characters of the sample, but also suppressed effectivly the nonradiative transitions, leading to the increased photon efficiency. The charge transfer transitions were dependent closely on the nonradiative transitions, while the formation of active oxygen and hydroxy on the adsorptive surface was independent of the nonradiative transitions.