Electrochemical Reduction of CO₂ Mediated by Quinone Derivatives: Implication for Li–CO₂ Battery

The pivotal role of CO2 played in global temperature cycles has motivated the ongoing research on carbon capture and storage (CCS). Within this context, Li–CO2 battery, alike the configuration of Li–O2 battery, has been proposed as a novel energy storage device with the potential to reduce CO2. Nevertheless, the highly negative potential required for the electrochemical reduction of CO2 adds difficulty to the achievement of energy efficient Li–CO2 battery. Facilitating the electron transfer to this inert molecule, which largely dictates the discharge voltage and rate capability of a Li–CO2 battery, is therefore necessary. Herein, three types of quinones have been surveyed, aiming to mediate the reduction of CO2, which is expected to result in lower overpotential than with a direct electron transfer. We demonstrate by cyclic voltammetry that, in the presence of quinones, CO2 reduction proceeds through an intermolecular interaction between CO2 and quinone dianion. Importantly, such catalytic CO2 reduction reaction is associated with the molecular structure of quinones, the supporting cation (e.g., Li+), and the electrolyte solvent. Furthermore, Li–CO2 battery mediated by 2,5-ditert-butyl-1,4-benzoquinone with Li2CO3 as the ultimate discharge product is achieved. This study validates the concept of using quinones as chemical catalysts to promote CO2 reduction in Li–CO2 battery. Besides, battery performance and NMR analysis together suggest that side reactions involving quinone itself and other cell components occur.