Atomistic and Oxophilic Ce Raises the Inertia of CO Intermediates Toward Enhanced Electrocatalytic Methanation

Selective and stable methane production via electrocatalytic CO₂ reduction (eCO₂R) utilizing membrane electrode assembly (MEA) has been challenging, requiring a delicate balance of surface coverage and binding energy among intermediates such as ^*CO and ^*H. This study addresses these challenges by doping oxophilic cerium (Ce) into a copper (Cu) matrix through thermal co-evaporation, creating atomistic CeO_χ-Cu^δ+ domains to promote bridged adsorption of ^*CO while pumping up the proton supply through enhanced water dissociation. The high inertia of ^*CO_bridge, as co-stabilized by ^*OH, and the high proton availability, effectively inhibit C─C coupling while prompting intermediates hydrogenation, ultimately leading to improved methane production. The optimized Ce_2%O_χ-Cu catalyst achieves an unprecedented stability in MEA operation for over 210 h with an average methane selectivity above 50%. This work offers profound understanding on synergistically tuning intermediates binding and water dissociation through oxophilic rare-earth doping to steer the eCO₂R pathway.