High-Yield Electrochemical Upgrading of CO2 into CH4 Using Large-Area Protonic Ceramic Electrolysis Cells: Article No. 121196

Electrochemical production of commodity chemicals via CO2-H2O co-electrolysis using solid oxide electrolysis cells presents a promising cost-effective energy-storage approach. Here, we harness the unique property of protonic ceramic electrolysis cells (PCEC) and demonstrate direct electrochemical production of CH4 from CO2-H2O in a PCEC unit-cell stack. An exceptional CH4-yield ratio of 34.6% from only CO2-H2O reactants and greater than 70% with exhaust H2 recycle were achieved under an electrolysis current of -1 A cm-2 at 450 degrees C. Additionally, the electrochemical co-conversion of CO2-H2O offered a higher CH4-yield ratio compared to the thermochemical conversion of CO2-H2 under certain operating conditions, indicating possible electrochemical promotion of catalytic CO2 methanation. Techno-economic analyses were conducted to reveal potential operating conditions that yield a promising levelized cost of fuel production. The demonstrated good performance of the unit-cell stack shows promising scalability of PCECs for practical application from a system-level viewpoint.