Integrated CO2 capture and conversion to form syngas

Abstract

To convert waste carbon dioxide (CO₂) into valuable chemicals and fuels, electrolyzers must be integrated with an upstream CO₂ capture step. However, this integration has not been demonstrated due to the mismatched rates between CO₂ capture and conversion. We present an integrated CO₂ capture-conversion system that produces syngas with a 1.7:1 H₂ to CO ratio at steady state, where the capture rate matches the release rate in the electrolyzer. The system uses a packed-bed absorber where K₂CO₃ solutions react with CO₂ from simulated flue gas to form (bi)carbonate-enriched solutions, which are then fed into an electrolyzer to produce CO and OH⁻. The alkaline product is recycled to the absorber, completing the CO₂ capture-conversion loop. With glycine as a CO₂ capture promoter, the system captures 30% of carbon from simulated flue gas with a Faradaic efficiency of 30% for CO₂ conversion to CO at 100 mA cm⁻² over 30 h.