Oxygen vacancies are omnipresent on an oxide surface under ambient conditions. The addition of fluorine to V2O5/TiO2 increases the number of oxygen vacancies which can react with O2 to form a superoxide species. The adsorption of NO and NH3 on the surface of the F-doped V2O5/TiO2 catalyst is investigated by electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Active oxygen species formed on the surface of the catalyst are detected by EPR. At 513 K, the adsorption of NO and NH3 possibly lies in the vicinity of the surface superoxide radicals, and leads to a change in the nearby electronic structure of these sites. The present results show that F-doping can form more oxygen vacancies on the surface of the catalyst. The oxygen vacancies play an important role in the catalytic conversion of the nitrogen oxides, because they can improve the adsorption and activation of NO, NH3 and O2. Additionally, the results of NO-TPD and NH3-TPD demonstrate that there is a close correlation between the adsorption amounts of NO or NH3 and the oxygen vacancy concentrations of the catalysts. The stability and lifetime of the surface O2− anions are directly correlated to the structure of the adsorption site on the catalyst surface and influence the catalytic ability of the catalyst to adsorb reaction gases under the NH3-SCR operating conditions.
在环境条件下,氧空位在氧化物表面上无处不在。在 V2O5/TiO2 中添加
氟会增加氧空位的数量,氧空位可以与 O2 反应形成超氧化物。通过电子顺磁共振(EPR)、X射线光电子能谱(XPS)和程序升温脱附(
TPD)研究了NO和NH3在F掺杂V2O5/TiO2催化剂表面的吸附。 EPR 检测催化剂表面形成的活性氧。在513 K时,NO和NH3的吸附可能位于表面超氧自由基附近,并导致这些位点附近的电子结构发生变化。结果表明,F掺杂可以在催化剂表面形成更多的氧空位。氧空位在氮氧化物的催化转化中起着重要作用,因为它们可以提高NO、NH3和O2的吸附和活化。此外,NO-
TPD和NH3-
TPD的结果表明NO或NH3的吸附量与催化剂的氧空位浓度之间存在密切的相关性。表面O2−阴离子的稳定性和寿命与催化剂表面吸附位点的结构直接相关,并影响催化剂在NH3-SCR操作条件下吸附反应气体的催化能力。