Integrated Copper/Alumina Heterojunction with Oxygen Vacancy Promotes the Activity and Selectivity of Electrochemical Methanation

Copper (Cu) can efficiently catalyze the CO₂ electrochemical reduction reaction (CO₂RR) to produce high-value-added fuels and chemicals, of which methane (CH₄) is of interest due to its high mass-energy density. However, the poor activity of Cu toward a specific product, as well as the relatively weak adsorption of ^*CO intermediates on the Cu surface, favors competitive ^*CO dimerization, thus limiting the selectivity for CH₄. Here, a heterojunction strategy is proposed by importing catalytically inert oxide containing oxygen vacancies to Cu (namely Cu_y/Al₂O_3- _x@C), which accelerates CO₂ electromethanation by altering the local geometries and electronic structures of catalysts, resulting in strong adsorption of ^*CO on the catalyst. By adjusting the composition of the catalyst, the Faraday efficiency (FE) toward CH₄ can be effectively nearly doubled from 39.2% to 74.6%. In situ Raman spectroscopy and Density functional theory (DFT) calculations reveal that oxygen vacancies in the catalyst can enrich proton donors and enhance the adsorption energy of ^*CO on the catalyst, thereby reducing the reaction energy barrier for the hydrogenation of ^*CO to CH₄. This work provided a new pathway for the Cu-based electrocatalyst design to achieve high selectivity by modulating the adsorption behavior of key intermediates.