Catalytic ativities of single-atom catalysts for CO oxidation: Pt1/FeOxvs. Fe1/FeOx

Abstract

An FeOx-based Pt single-atom catalyst (SAC), Pt1/FeOx, has stimulated significant recent interest owing to its extraordinary activity toward CO oxidation. The concept of SAC has also been successfully extended to other FeOx supported transition metal systems both experimentally and theoretically. However, the FeOx substrate itself (denoted by Fe1/FeOx following the same nomenclature of Pt1/FeOx) as a typical transition metal oxide possesses a very low catalytic activity toward CO oxidation, although it can be viewed as Fe1/FeOx SAC. Here, to understand the catalytic mechanism of FeOx-based SACs for CO oxidation, we have performed density functional theory calculations on Pt1/FeOx and Fe1/FeOx for CO oxidation to address the differences between these two SACs in terms of the catalytic mechanism of CO oxidation and the chemical behavior of the catalysts. Our calculation results indicated that the catalytic cycle of Fe1/FeOx is much more difficult to accomplish than that of SAC Pt1/FeOx because of a high activation barrier (1.09 eV) for regeneration of the oxygen vacancy formed when the second CO2 molecule desorbs from the surface. Moreover, density of states and Bader charge analysis revealed differences in the catalytic performance for CO oxidation by the SACs Fe1/FeOx and Pt1/FeOx. This work provides insights into the fundamental interactions between the single-atom Pt1 and FeOx substrate, and the exceptional catalytic performance of this system for CO oxidation.