A general descriptor for guiding the electrolysis of CO2 in molten carbonate
Zhengshan Yang, Bowen Deng, Kaifa Du, Huayi Yin, Dihua Wang
Abstract
Molten carbonate is an excellent electrolyte for the electrochemical reduction of CO2 to carbonaceous materials. However, the electrolyte–electrode-reaction relationship has not been well understood. Herein, we propose a general descriptor, the CO2 activity, to reveal the electrolyte–electrode-reaction relationship by thermodynamic calculations and experimental studies. Experimental studies agree well with theoretical predictions that both cations (Li+, Ca2+, Sr2+ and Ba2+) and anions (BO2−, Ti5O148−, SiO32−) can modulate the CO2 activity to control both cathode and anode reactions in a typical molten carbonate electrolyzer in terms of tuning reaction products and overpotentials. In this regard, the reduction of CO32− can be interpreted as the direct reduction of CO2 generated from the dissociated CO32−, and the CO2 activity can be used as a general descriptor to predict the electrode reaction in molten carbonate. Overall, the CO2 activity descriptor unlocks the electrolyte–electrode-reaction relationship, thereby providing fundamental insights into guiding molten carbonate CO2 electrolysis.