Direct electroreduction of flue gasses: Progress and economic analysis

Electrochemical reduction reaction of pure CO2 (epCO2RR) is highly promising since it could convert CO2 pollution into value-added chemicals (e.g., CO, HCOOH, C2H4, C2H5OH) under industrial-level current density with high selectivity above 90 %. While the purification process of industrial flue gas into pure CO2 accounts for significant portion of CO2-electrolysis cost. Direct flue-gas electroreduction offers a cost-effective alternative, while its practical implementation faces challenges such as low CO2 concentrations (<20 vol%) leading to small current density, competitive reactions such as oxygen reduction reaction, hydrogen evolution reaction, etc., with more positive thermodynamic potentials than epCO2RR. Therefore, this work reviews strategies to develop efficient and selective electrocatalysts that are resistant to non-CO2 active gasses such as O2, SOx, NOx, etc., and treatment methods for such components in the flue gas. Significantly, the technoeconomic analysis of CO2 capture and purification integrated electrolysis process and direct flue gas reduction, is compared. Importantly, future research regarding direct electrochemical reduction of flue gas is proposed, including multifunctional catalyst design, complex reaction mechanism exploration, electrolysis system optimization, etc.