Impurity-Resistant CO₂ Reduction Using Reactive Carbon Solutions

Electrolyzers that electrochemically convert aqueous (bi)carbonate solutions (solutions containing captured CO 2, or “reactive carbon solutions”) into commodity chemicals couple CO 2 capture with CO 2 conversion. Industrial exhaust streams contain nitrogen oxides (NO x ) and sulfur oxides (SO x ) that form redox-active anions in reactive carbon solutions that can interfere with downstream CO 2 reduction. We therefore designed experiments to test how impurities produced from the dissolution of NO x (NO 2 – and NO 3 – ) and SO x (SO 3 2– and SO 4 2– ) impact the electrochemical conversion of (bi)carbonate to CO. We found that CO production was unaffected by SO x compounds in a 3.0 M KHCO 3 feedstock, but 2000 ppm of NO x impurities decreased CO selectivity from ∼60% to <5%. This decrease was caused by the preferential reduction of NO 2 – and NO 3 – over CO 2 . Our study establishes tolerance limits for common flue gas impurities in reactive carbon solutions and provides strategies to mitigate toxification effects.