Probing the electronic structure and photoactivation process of nitrogen-doped TiO2 using DRS, PL, and EPR.
Probing the electronic structure and photoactivation process of nitrogen-doped TiO2 using DRS, PL, and EPR.
复制标题
DOI：
10.1002/cphc.201100991
复制
发表时间：
2012-04
期刊：
影响因子：
--
通讯作者：
Zizhong Zhang;Jinlin Long;Xiuqiang Xie;Huan Lin;Yangen Zhou;Rusheng Yuan;W. Dai;Z. Ding;Xuxu Wang;Xianzhi Fu
中科院分区：
文献类型：
--
作者：
Zizhong Zhang;Jinlin Long;Xiuqiang Xie;Huan Lin;Yangen Zhou;Rusheng Yuan;W. Dai;Z. Ding;Xuxu Wang;Xianzhi Fu
研究了氮掺杂二氧化钛的电子结构和光活化过程。利用漫反射光谱(DRS)、光致发光光谱(PL)和电子顺磁共振(EPR)技术研究了热诱导和光诱导N掺杂的TiO2光催化剂光吸收能力的变化以及N物种和缺陷的形成。当热处理温度低于573K时，掺杂样品中的氮不会被去除，但会形成氧空位和Ti(3+)态来增强可见光区域的光吸收，特别是500 nm以上波长的光吸收随温度的升高。在N掺杂的TiO2光活化过程中，450-700 nm可见光区的DRS吸收和荧光发射随光照时间的延长而增加。电子顺磁共振谱结果表明，在光照下产生了顺磁性氮物种(N(S)·)、单电子氧空位(V(O)·)和Ti(3+)离子，且N(S)·物种的强度与激发光波长和功率有关。综合表征结果证实，掺杂N物种的能级集中在410 nm处的主吸收带对应的价带之上，但氧空位和Ti(3+)态作为缺陷对样品的可见光吸收贡献大于500 nm。在此基础上，提出并讨论了掺氮二氧化钛的电子结构。另一方面，在催化剂表面，载流子在氮物种和缺陷之间的转移是可逆的。氧空位相关缺陷的存在导致顺磁性N(S)·物种的猝灭，但它们稳定了活性氮物种N(S)(-)。
The electronic structure and photoactivation process in N-doped TiO(2) is investigated. Diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and electron paramagnetic resonance (EPR) are employed to monitor the change of optical absorption ability and the formation of N species and defects in the heat- and photoinduced N-doped TiO(2) catalyst. Under thermal treatment below 573 K in vacuum, no nitrogen dopant is removed from the doped samples but oxygen vacancies and Ti(3+) states are formed to enhance the optical absorption in the visible-light region, especially at wavelengths above 500 nm with increasing temperature. In the photoactivation processes of N-doped TiO(2), the DRS absorption and PL emission in the visible spectral region of 450-700 nm increase with prolonged irradiation time. The EPR results reveal that paramagnetic nitrogen species (N(s)·, oxygen vacancies with one electron (V(o)·), and Ti(3+) ions are produced with light irradiation and the intensity of N(s)· species is dependent on the excitation light wavelength and power. The combined characterization results confirm that the energy level of doped N species is localized above the valence band of TiO(2) corresponding to the main absorption band at 410 nm of N-doped TiO(2), but oxygen vacancies and Ti(3+) states as defects contribute to the visible-light absorption above 500 nm in the overall absorption of the doped samples. Thus, a detailed picture of the electronic structure of N-doped TiO(2) is proposed and discussed. On the other hand, the transfer of charge carriers between nitrogen species and defects is reversible on the catalyst surface. The presence of oxygen-vacancy-related defects leads to quenching of paramagnetic N(s)· species but they stabilize the active nitrogen species N(s)(-).