A theoretical study on the promotion of methane activation by adsorption of O species on Cu/CeO2(111)

Abstract

A first-principles theoretical study was performed to elucidate the activation dissociation of CH₄ on a Cu₄ cluster supported by CeO₂(111), including the activation of CH₄ by the Cu cluster, Cu cluster and CeO₂ interface, and adsorbed O species. During the C–H bond cleavage of CH₄, CH₃ tends to adsorb on Cu atoms instead of forming a radical and the corresponding energy barrier and reaction heat are 1.56 eV and −0.20 eV, respectively. Although CH₃ + H intermediates have higher stability on the Cu cluster compared to that at the interfacial O site, they have a lower activation energy of 1.11 eV at the interface. When there is a pre-adsorbed O atom or an OH group on the surface, it was found that both of them can effectively facilitate the C–H bond cleavage in their own way. The O atom can reduce the activation barrier by 0.72 eV or 0.22 eV to form a CH₃O product or an OH product, while the OH group can reduce the activation barrier by 0.60 eV to form a H₂O product. The promotion of O and OH is mainly related to the stabilization of transition state structures.