A DFT+U study on the oxidative chlorination of CH4 at ceria: the role of HCl

Abstract

The effects of HCl on the oxidation of CH₄ at CeO₂(111) have been studied by using density functional theory calculations corrected by on-site Coulomb interactions (DFT+U). The calculated results show that the presence of HCl barely affects the CH₄ dissociation, but can provide new reaction channels to produce CH₃Cl. The effects of surface defects and orientations on the surface reactivity were also considered. The total oxidation of CH₄ can be partially prohibited by the high barriers for the further dissociation of CH₃ at reduced surfaces due to the strong electronic repulsion of heavily accumulated localized electrons. CeO₂(110) shows higher activity and selectivity for CH₃Cl formation than CeO₂(111), indicating that the morphologies of CeO₂ nanocatalysts would be key to the catalytic activities toward CH₄ activation.