NO在MgO(001)缺陷表面吸附解离的量子化学研究

在密度泛函理论框架下,采用嵌入点电荷簇模型研究了NO在MgO(001)完整和缺陷表面上的吸附。研究结果表明:具有氧缺陷结构表面的催化活性较高,有利于NO键的削弱;当另一个NO分子进攻已吸附的NO分子时,NO键将进一步削弱,直致断裂,并伴有N2O产生,这与UPS和MIES实验观察到的现象一致。Mulliken布居分析指出,底物电子向NO转移,并填充到NO的*反键轨道上,从而导致NO键的削弱,并形成NO-。这也是可能导致形成NO-的原因。研究还表明,具有镁缺陷的MgO(001)表面对NO的解离没有催化活性。

Theoretical Study of NO Adsorptive-decomposition on MgO(001) Surface with Vacancies

The adsorption of NO adsorbed on MgO(001) perfect and defect surfaces has been studied by using cluster models embedded in a lot of point charges(PC) with DFT/B3LYP method at the 6-31G(d) basis set level. The calculated results indicate that the surface with various oxygen vacancies has the high catalytic reactivity for NO dissociation. Besides, it is found that the NO bond will be broken when another NO molecule approaches the adsorbed NO with concurrent production of N2O, which is consistent with the phenomenon of MIES and UPS experiments. Mulliken population analysis shows that the electron transfer from the substrate to the anti-bonding * orbital of adsorbed NO is the essential reason for the weakening of NO bond. This can also cause the production of NO-. At the same time, the MgO(001) surface with magnesium vacancies exhibits almost no reactivity for NO dissociation.