Low-Energy Electrochemical Carbon Dioxide Capture Based on a Biological Redox Proton Carrier

Carbon capture and storage, in which CO 2 is selectively removed and sequestrated from flue gas, is a promising strategy to mitigate CO 2 emissions and global warming. Conventionally, CO 2 capture involves an energy-consuming absorbent regeneration step by thermal decomposition (2.0–4.0 GJ ton −1 CO 2 ), which accounts for the majority (60%–70%) of the total cost. Here, we propose an alternative electrochemical cycle to capture CO 2 in an aqueous alkaline solution, facilitated by the pH swing effect from a proton-coupled electron transfer redox reaction of a biological proton carrier, riboflavin 5′-monophosphate sodium salt hydrate (FMN/FMNH 2 ). Under lab conditions, an electrolysis cell implementing the FMN proton carrier demonstrates a high energy efficiency, with only 9.8 kJ mol −1 CO 2 captured, which is much lower than traditional approaches using a monoethanolamine absorbent (2.0–4.0 GJ ton −1 CO 2 , 88–176 kJ mol −1 CO 2 ). Thus, this system may contribute toward lowering the cost of CO 2 capture.