Au-Decorated Silicene: Design of a High-Activity Catalyst toward CO Oxidation

First-principles calculations have been performed to study Au-decorated silicene (Au/silicene) as a high-activity catalyst for CO oxidation. The high binding strength of the Au/silicene system and the high diffusion-energy barrier of Au adsorbates, as well as the assisted Coulomb repulsion effect, jointly prevent the formation of Au clusters. Au/silicene transfers many more electrons to O-2 than to CO, thus facilitating CO oxidation first by the Langmuir-Hinshelwood (LH) mechanism (CO + O-2 -> OOCO -> CO2 + O) and then by Eley-Rideal (ER) mechanism (CO + O -> CO2). The two reaction processes have quite low catalytic energy barriers of 0.34 and 0.32 eV, respectively. The underlying mechanism of high catalytic oxidation of CO can be attributed to electronic-state hybridization among Au d orbitals and CO and O-2 2 pi* antibonding states around the Fermi energy. These findings enrich the applications of Si-based materials to the high-activity catalytic field.