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

Abstract

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 Agx@Au-(111) and Agx@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 O2 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 electr...