Promoting reducibility and activity of Cu by tuning oxygen defects on ceria for selective electrochemical CO 2 reduction to methane

Electrocatalytic reduction of CO 2 (CO 2 RR) to valuable fuels or chemical feedstock provides a potential pathway to reach a carbon-neutral economy and address environmental issues. However, selectively reducing CO 2 to methane with high energy density remains a big challenge. The synergistic effect of Cu/oxide active sites and substrates at the interface plays an important role in the catalytic performance. Herein, annealed cerium oxide nanorods (CeO 2− x ) loaded with Cu were synthesized and showed high catalytic selectivity to methane. The Faradaic efficiency of CH 4 reached 52.7% at −1.8 V vs. RHE, in a H-type electrolytic cell. Detailed studies suggested that the enhanced performance of Cu–CeO 2− x was attributed mainly to the reducibility of Cu species modulated by a high concentration of oxygen vacancies on annealed CeO 2− x , which stabilized highly efficient active sites for the electroreduction of CO 2 to methane.