CO诱导的FeO(111)/Ru(0001)负载Au原子吸附位和电荷的改变

采用密度泛函理论研究了CO气氛对FeO(111)/Ru(0001)负载Au原子吸附位、电荷及其稳定性的影响. 首先考察了FeO(111)单层薄膜在Ru(0001)表面上的界面结构. 研究发现,表面莫尔超晶胞内的HCP区域有最小的Fe-O层间距(rumpling),且Fe和O原子均与衬底Ru形成化学键. Au原子在FeO/Ru(0001)上最稳定的吸附在HCP区域的Fe-bridge位. 其中,Au原子诱导两个Fe原子从O原子层的下面翻转到其上面,形成两个Au-Fe键,且Au带负电. 当把体系暴露在CO气氛下后,CO能诱导Au原子从原来最稳定的Fe-bridge位转移到其邻近的O-top位,伴随着Au的电荷从负变到正,形成非常稳定的Au⁺-CO羰基物. 结果表明,反应气氛对负载金属催化剂的化学状态及其稳定性的影响很大; 同时也强调了反应条件下催化剂原位表征的重要性.

Adsorbed CO induced change of the adsorption site and charge of Au adatoms on FeO(111)/Ru(0001)

A first principles study of the influence of CO adsorption on the charge state, adsorption site, and stability of Au adatoms on FeO/Ru(0001) was presented. Calculations were first carried out to explore the detailed interface structure of a bilayer FeO(111) film on Ru(0001). The HCP domain inside the Moire supercell has a rather small rumpling with both the Fe and O atoms directly bonded to the Ru substrate. The most stable adsorption of an Au atom on FeO/Ru(0001) is at the Fe-bridge site in the HCP domain, where Au binds with two flipped Fe atoms and is negatively charged. After exposure to CO, the Au anions at the Fe-bridge site changed their position to the O-top site by overcoming a small barrier of only 0.12 eV, where they formed stable Au⁺-CO species with a significant reduction in the formation energy. The results highlighted the importance of in situ characterization of supported catalysts under reaction conditions, and implications on catalyst stability were also discussed.