Largely Promoted C–H Activation in Methane with O2 via d-Orbital Hybridization Induced by CuOx Supported on ZnO

Abstract

Efficiently converting methane (CH₄) to C1 products such as CH₃OH, HCHO, and CH₃OOH is considered a promising route for the chemical industry, while the huge challenge of low CH₄ activation rate still remains. Here, the promising Cu/ZnO composite catalyst with CuO_x supported on ZnO is synthesized to modify the electronic structure and utilized for CH₄ conversion. The fast e^– transfer channel of ZnO → Cu → O₂ facilitates O₂ dissociation to ^•OOH, which promotes charge separation and, in parallel, enables CH₄ oxidation to ^•CH₃ by h⁺ left in ZnO with the acceleration effect of in situ generated ^•OOH. Mechanistic studies revealed that additional d-π*/d-σ-orbital hybridization between the catalyst and adsorbed O₂/CH₄ molecules plays decisive roles in O₂ and CH₄ activation, which resulted in the highest ^•CH₃ signal, so far as we know, and ultimately a remarkably high C1 products yield of 21.25 mmol g^–1 h^–1 with 100% selectivity over the optimized 1 wt % Cu/ZnO photocatalyst. This work offers valuable guidance for catalyst designation in CH₄ conversion in the presence of O₂.