A CO2-Assisted Sodium-Phenanthrenequinone Battery.

Future society will need more energy storage than what the current technology can deliver and also need more efficient approaches to mitigate CO2 emission and its consequent climate change. Here we report a new concept of sodium-phenanthrenequinone (Na-PQ) battery that can capture CO2 to heighten its load voltage and specific energy upon discharge and reversibly release CO2 on recharge. A mechanistic study, combining spectroelectrochemistry and theoretical calculation, reveals that CO2 is involved in the discharge reaction by bonding to the carbonyl moieties (C═O) of the reduced PQ species (PQ2- in particular), which lowers the energy of the final discharge product PQ2-CO2(Na+)2 and therefore increases the formal potential of the redox couple PQ-Na+/PQ2-CO2(Na+)2. The CO2-assisted Na-PQ battery reported here exemplifies that electrochemical energy storage would have great potential to address one of the grand challenges (i.e., CO2 mitigation, utilization, and storage) facing human society in the 21st century and beyond.