TiO_2表面氧空位对NO分子吸附的作用

Effects of the oxygen vacancy on NO adsorption at the TiO_2 surface

采用程序升温热脱附 (TPD)实验方法测定了NO在TiO2 表面吸附后的脱附谱 ,利用分子轨道理论研究了TiO2吸附NO的原子簇模型及吸附前后的原子簇能级变化 .结果表明 ,NO在TiO2 表面吸附后可在两个峰值温度 4 5 0和980K脱附出N2 .TiO2 表面经预覆氧处理后 ,N2 的脱附量降低 .吸附时NO中的O能够占据TiO2 表面氧空位并与N脱离 ,而N原子则相互结合成为N2 脱附 .分子轨道理论计算证明在TiO2 (110 )表面能够存在氧空位并具备吸附NO的结构条件 .

The desorption spectrum of NO adsorbed on the surface of TiO2 (powder was determined by temperature programmed desorption. The molecular orbital theory was utilized to investigate the crystal cluster model of NO adsorbed on TiO)(2) (and the change of band gap in the adsorption process. The results indicate that there exist two peak temperatures, 450 and 980K, as N)(2) (desorption followed by the NO adsorption on TiO)(. The intensity of N)(2)(2) (desorption decreases if the TiO)(2) (powder is pretreated in an O)(2) (atmosphere. The nitrogen atoms of the adsorbed NO gas recombine into N2 for desorption while oxygen atoms occupy the oxygen vacancies in the TiO)(2) (surface. The calculation analysis from the molecular orbital theory supports the deduction that the existence of oxygen vacancy on TiO)(2)(110) surface offers a suitable condition of crystal surface for NO adsorption.