Capture and electro-splitting of CO2 in molten salts

Due to the serious greenhouse gas effects caused by the increasing concentration of atmospheric CO2, carbon capture and storage (CCS) has been an important area of research and many technologies are developed within this field. Molten salt CO2 capture and electrochemical transformation (MSCC-ET) process is a desirable method due to a high CO2 solubility, a wide potential window of molten salts and easily-controlled electrode reactions. Generally, electro-splitting CO2 in molten salts begins with CO2 absorption reactions to form CO32−, which is then followed by the carbon deposition at the cathode and O2 evolution at the anode. As a result, CO2 is electro-converted to O2 and carbon with different morphologies, compositions, microstructures and functional properties. This report introduces the MSCC-ET process, summarizes the reactions occurring in the molten salts and at the electrode surfaces, as well as the morphological variations of the cathodic products. The inert anode materials, cost estimation and scale-up evaluation of the process are then discussed. It is presumed that with a comprehensive understanding of the electrode reactions during electrolysis and the functional properties of carbon materials obtained during CO2 electro-splitting can provide a foundation for further developing this environmentally friendly process.