旨在探究N掺杂纳米TiO2具有可见光活性的本质,采用XPS、ESR、XRD、SEM、DRS、SPS和PL分析技术对sol-gel法制备的未掺杂和N掺杂TiO2纳米粉体进行了对比研究,并以亚甲基蓝(MB)溶液在可见光下的光催化脱色评价其可见光活性.结果表明,N掺杂TiO2纳米粉体具有良好的可见光活性,未掺杂样品几乎没有可见光活性.N取代TiO2晶格中O形成了N-Ti-O和O-N-Ti键合结构产生杂质能级,N掺杂导致TiO2表面形成了大量束缚单电子的氧空位产生缺陷能级,二者协同作用致使带隙窄化,光吸收带边红移,产生可见光活性.N掺杂导致TiO2晶格中p-n结的形成及表面氧空位和表面羟基的增加均能促进光生e-/h+分离,有效抑制光生e-/h+复合,提高量子效率,进而提高其光活性.%A comparative study on un-doped and N-doped TiO2 nano-particles prepared by a sol-gel method was carried out by the analytic techniques such as X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), X-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis diffuse reflection spectra (DRS), surface photovoltage spectra (SPS) and photoluminescence spectra (PL), in order to explore the origin of visible-light photoactivity for N-doped nano-TiO2. Their visible-light photoactivities were evaluated by the photocatalytic decoloring of methylene blue (MB) in aqueous solution under visible-light irradiation. The results show that the N-doped sample exhibits a good visible-light photoactivity, whereas the un-doped sample has little visible-light photoactivity. The visible-light response of the N-doped TiO2 nanoparticles is ascribed to a synergetic effect of impurity energy levels due to the substitutional N-doping forming the N-Ti-O and O-N-Ti bonding structures and defect energy levels resulted from the formation of oxygen vacancies, which result in the band-gap narrowing and red-shift of optical absorption band. The separation of the photo-generated e-/h+ can be accelerated by the formation of p-n junctions in crystal lattice of TiO2 and the increase in both oxygen vacancies and surface hydroxyl groups resulted from N-doping. As a result, they can inhibit the recombination of the photo-generated e-/h+ effectively and enhance the quantum efficiency, then increasing the photoactivity.
展开▼
