Integrated capture and electrochemical conversion of CO2 from flue gas mediated by carbonate/bicarbonate cycle

Abstract

Capturing the excessively emitted CO2 and converting it through electrochemistry into value-added chemicals represents a promising approach to mitigate CO2 emission and close the carbon cycle. Currently, these two processes are performed independently, involving multiple operation steps and requiring large energy consumption. Here, we report an effective strategy to integrate the capture and electrochemical conversion of CO2 from flue gas by exploiting the interconversion between K2CO3 and KHCO3. We show that the direct conversion of KHCO3 solution can produce CO at high selectivity over carbon-supported molecular catalysts and single-atom catalysts. The in-situ generated CO2 in KHCO3 solution is evidenced to be the real reactant for CO production through kinetic analysis, comparative experiments, and in-situ Raman spectroscopy. We demonstrate that the CO2-captured K2CO3 solution (containing KHCO3) can be efficiently electrolyzed to produce syngas (CO and H2) and restore partially the original K2CO3 solution, which can be used to capture CO2 again. We accomplish the continuous and stable integration of CO2 capture (48 h) and electrochemical conversion (96 h) for a prolonged period. The energy analysis reveals that integrating CO2 capture and the electrolytic conversion through the K2CO3⇌KHCO3 interconversion can significantly reduce energy consumption. This work provides a new and promising pathway for energy-efficient carbon capture and utilization.