Highly efficient, coke-free electrolysis of dry CO2 in solid oxide electrolysis cells

Dry CO2 electrolysis in solid oxide electrolysis cells (SOECs), a highly efficient, versatile method for converting CO2 into value-added products, is critically limited by carbon deposition on Ni-based fuel electrodes. We achieved efficient, coke-free CO2 electrolysis using SOECs by elaborately controlling the local gas environments. Multilayered electrode microstructures were systematically engineered to facilitate mass transport and maintain the CO partial pressure below the threshold for solid carbon formation. A fuel-electrode-supported cell with an improved electrode microstructure operated stably for 500 h without coking at 0.50 A cm−2 and 700 °C, whereas conventional ones failed immediately. Multiphysics modeling coupled with three-dimensional quantitative microstructural analysis confirmed our improved electrode successfully mitigated carbon deposition. Furthermore, the enhanced electrode substantially lowered the overpotential and increased the CO production rate by > 50 %. These results highlight the feasibility of coke-free dry CO2 electrolysis in SOECs using commercially viable materials by controlling the electrode transport properties.