Density Functional Theory (DFT) Studies of CO Oxidation over Nanoporous Gold: Effects of Residual Ag and CO Self-Promoting Oxidation

作者：Wang, Pu; Tang, Xianqiong; Tang, Jian; Pei, Yong^*

来源：Journal of Physical Chemistry C, 2015, 119(19): 10345-10354.

DOI：10.1021/jp5124376

We report a systematic study of CO oxidation mechanism over nanoporous (NPG) using the density functional theory (DFT). In the study, the (111) and (100) flat planes that were identified as the most abundant in the nanoporous gold are mimicked by Ag-x@Au-(111) and Ag-x@Au-(100) slabs (x = 1 - 3). A total of 50 reaction pathways are examined at different active sites. A simplified microkinetics model termed the Sabatier analysis, which is built on the adsorption energies and activation barriers, is used to evaluate the reaction rate of different reaction pathways. Our theoretical results indicate that the Au-kink sites joining the (111) and (100) flat planes are the major active sites. The residual Ag atoms in the Au-kink site promote the adsorption of O-2 species and hence increase the reaction rate of CO oxidation. Besides the discussion of the Ag-impurity effect, we also propose that the nearby coadsorbed CO at Au steps can promote the dissociation of OCOO* reaction intermediate significantly via an electrophilic attack process, which is denoted as a trimolecular CO self-promoting oxidation mechanism. The trimolecular route has reduced reaction steps and higher reaction rate in comparison to the conventional bimolecular reaction mechanism.

• 出版日期2015-5-14
• 单位湘潭大学