Electrochemical and Molecular Assessment of Quinones as CO ₂ -Binding Redox Molecules for Carbon Capture

Abstract

The complexation and decomplexation of CO2 with a series of quinones of different basicity during electrochemical cycling in dimethylformamide solutions were studied systematically by cyclic voltammetry. In the absence of CO2, all quinones exhibited two well-separated reduction waves. For weakly complexing quinones, a positive shift in the second reduction wave was observed in the presence of CO2, corresponding to the dianion quinone–CO2 complex formation; there was no formation of complexes between the semiquinones and CO2. For strongly complexing quinones, the second reduction wave merged with the first, indicating that the two electrons transferred simultaneously at this potential. Both weakly and strongly complexing quinones underwent oxidation and CO2 dissociation with the order depending on the sweep rate in the cyclic voltammetric experiments, termed either electrochemical–chemical or chemical–electrochemical. This study provides an interpretation of the interactions that lead to the formation of quinone–CO2 complexes required for the potential development of an energy efficient electrochemical separation process and discusses important considerations for practical implementation of CO2 capture in the presence of oxygen with lower vapor pressure solvents.