Selective Oxidative Coupling of Methane to Ethylene in a Solid Oxide Electrolyser Based on Porous Single‐Crystalline CeO2 Monoliths

Catalytic conversion of CH4 to C2 H4 plays an important role in the light olefin industry. Here, we report the electrochemical conversion of CH4 to C2 H4 /C2 H6 at the anode with the electrolysis of CO2 to CO at the cathode in a solid oxide electrolyser. We constructed well-defined interfaces that function as three-phase boundaries by exsolving single-crystalline Ni nanoparticles in porous single-crystalline CeO2 monoliths. We engineered the chemical states and flux of active oxygen species for the oxidation of CH4 at the anode by controlling voltage and temperature. We show the unprecedented C2 selectivity (C2 H4 and C2 H6 ) of ≥99.5 % at a CH4 conversion of ≈7 %. The electrolyser exhibits excellent durability without performance degradation being observed in a continuous operation of 100 hours. Our work enables a novel path for the selective conversion of CH4 /CO2 into useful chemicals, and the technique of building well-defined interfaces may find potential applications in other fields.