Surface Oxygen Vacancy and Hydride Species on Ceria Are Detrimental to Acetylene Semihydrogenation Reaction
Zhaorui Li, Lu Chen, Zongfang Wu, Aiping Jia, Shucheng Shi, Hui Zhang, Jia Wang, Zhi Liu, Wei-Peng Shao, Fan Yang, Xin‐Ping Wu, Xue‐Qing Gong, Weixin Huang
Abstract
Reactivity of OH and hydride species in oxide-catalyzed hydrogenation reactions has attracted great interest. Herein, we report a combined in situ spectroscopic characterization and density functional theory (DFT) calculation study of ceria-catalyzed acetylene semihydrogenation reaction. The ceria surface is fully hydroxylated during the adopted reaction condition. C 2 H 2 adsorbs molecularly on the stoichiometric CeO 2 surface and hydrogenates with OH groups selectively to produce C 2 H 4 . Semihydrogenation of C 2 H 2 to C 2 H 4 with either OH groups or hydride species on ceria surfaces with surface oxygen vacancies proceeds more facilely than on a stoichiometric CeO 2 surface, but C 2 H 4 adsorbs more strongly and further hydrogenates to C 2 H 6 more facilely; moreover, dissociative adsorption of C 2 H 2 to C 2 H species occurs, which facilely hydrogenates with the hydride species eventually to form C 2 H 6 and react with each other to produce oligomers, decreasing the catalytic selectivity and stability, respectively. These results demonstrate that the ceria catalyst with a stoichiometric surface is extremely selective in catalyzing C 2 H 2 semihydrogenation reaction to C 2 H 4, whereas surface oxygen vacancies or hydride species on ceria are harmful to the catalytic performance.