Theoretical Study of CO Oxidation over Au1/MgO(100) with Different Vacancies

Abstract

The CO catalytic oxidation over Au1/MgO(100) with different vacancies is studied by means of the density functional theory (DFT) and microkinetic modeling. Through comprehensively sampling the reaction pathways, including the Langmuir-Hinshelwood (LH), Eley−Rideal (ER), tri-molecular Eley-Rideal (TER) and Mars van Krevelen (MvK) mechanisms, and calculating the conversion rate of the CO2 at different thermodynamic conditions by microkinetic modeling, the catalytic activities of the single Au atom adsorbed on the different MgO surfaces are evaluated. The microkinetic modeling results indicated that the Au atom adsorbed on the defect-free MgO (Au1/defect-free MgO) is easily poisoned by the CO, showing quite low activity toward CO oxidation. The Au atom trapped in the F-center (Au1/F-center) has high catalytic activity towards the CO oxidation via the tri-molecular ER mechanism, while the catalyst suffered stability issue that the F-center easily transformed into the defect-free MgO in the presence of dangling O atom. For the V-center trapped Au atom (Au1/V-center), a unique carbonyl modified single Au atom active site (denoted as 2CO-Au1/V-center) is identified. It demonstrates high catalytic activity toward CO oxidation via either tri-molecular ER or bi-molecular LH reaction mechanism. The microkinetic modeling revealed that the 2CO-Au1/V-center is very beneficial for CO2 production at the ambient temperature with optimal pressure of CO and O2.