CeO_2(110)表面上CO氧化反应的密度泛函理论研究  

A Density Functional Theory Study of CO Oxidation on CeO_2(110) Surface

作　　者：滕波涛[1] 蒋仕宇[1] 郭晓伟[1] 袁金焕[1] 罗孟飞[1] 

机构地区：[1]浙江师范大学物理化学研究所浙江省固体表面重点实验室,金华321004

出　　处：《化学学报》2009年第24期2765-2772,共8页Acta Chimica Sinica

基　　金：国家自然科学基金(No.20903081);浙江省自然科学基金(Nos.Y407163;Y407020)资助项目

摘　　要：利用密度泛函理论系统研究了O2与CO在CeO2(110)表面的吸附反应行为.研究表明,O2在清洁的CeO2(110)表面吸附热力学不利,而在氧空位表面为强化学吸附,O2分子被活化,可能是重要的氧化反应物种.CO在清洁的CeO2(110)表面有化学吸附与物理吸附两种构型,前者形成二齿碳酸盐物种,后者与表面仅存在弱相互作用.在氧空位表面,CO可分子吸附或形成碳酸盐物种,相应吸附能均较低.当表面氧空位吸附O2后(O2/Ov),CO可吸附生成碳酸盐或直接生成CO2,与原位红外光谱结果相一致.过渡态计算发现,O2/Ov/CeO2(110)表面的三齿碳酸盐物种经两齿、单齿过渡态脱附生成CO2.利用扩展休克尔分子轨道理论分析了典型吸附构型的电子结构,说明表面碳酸盐物种三个氧原子电子存在离域作用,物理吸附的CO及生成的CO2电子结构与相应自由分子相似.CO oxidation reaction on the CeO2（110） surface was systematically investigated using a density functional theory （DFT） method. It was found that O2 adsorption on the clean CeO2（110） surface was thermodynamically unfavorable. When surface oxygen vacancy existed, strong adsorption occured and the O2/Ov species formed, which might be one of the most important oxygen species for oxidative reaction. Chemisorbed and physisorbed CO adsorption configurations were observed on the clean CeO2（110） surface. The former formed a bidentate carbonate intermediate; while only weak interactions occured between CO and CeO2（110） surface for the latter. On the CeO2（110） surface with oxygen vacancy, both carbonate species and molecular CO were obtained with low adsorption energies. When O2 adsorbed on the surface with oxygen vacancy （O2/Ov）, CO might strongly adsorb on the surface to form a carbonate intermediate, or directly produce CO2. It was very interesting to find that the carbonate species on the O2/Ov/CeO2（110） surface desorbs to CO2 through the bidentate and monodentate intermediates. According to the extended Hückel （eH） theory, the electrons of three oxygen atoms of the carbonate intermediate underwent partial delocalization. The electronic structures of the physisorbed CO and CO2 product on the CeO2（110） are much similar to those of free molecules.

关 键 词：CO氧化 CeO2(110)表面 密度泛函理论 扩展休克尔分子轨道理论 

分 类 号：O643.12[理学—物理化学]