Electrochemical condition optimization and techno-economic analysis on the direct CO2 electroreduction of flue gas

Direct CO2 electroreduction of flue gas is a technology that simplifies CO2 capture and purification process and directly utilizes CO2 in flue gas. Low CO2 reduction reaction selectivity caused by the low CO2 partial pressure and side reactions competition is the challenge. In this study, a direct CO2 electroreduction system for multicomponent flue gases was established. A two-dimensional steady model was developed by considering major electrode reactions of flue gas in CuxO-based catalysts. General influence criteria and optimum operation window for the potential, temperature, and pressure were proposed. In addition, a techno-economic analysis of the flue gas electrolysis system was conducted. The results demonstrated that the CO2 electroreduction reaction performances are weak at atmospheric pressure owing to the side reaction competition and small reactant concentration. A method involving pressurization and catholyte inlet temperature declination is proposed to break the stalemate of tiny reactant concentrations and ensure the dominance of the CO2 electroreduction reaction. The selectivity and current density of the CO2 reduction reaction were 71% and − 148 mA/cm2 at −1.17 V vs. reversible hydrogen electrode potential (RHE), respectively, under the conditions of an inlet electrolyte temperature of 273 K and an operating pressure of 20 atm. C1 products with excellent yields are the dominant products. Furthermore, the techno-economic analysis showed that the flue gas electrolysis system has higher profitability and lower cost than the purified CO2 electrolysis system. The present results can be used to optimize the electrolyzer operating parameters and construct CO2 reduction systems.