持続可能なエネルギーで大気中の CO2 を除去

Electrochemical CO₂ capture technologies are gaining attention due to their flexibility, their ability to address decentralized emissions (e.g., ocean and atmosphere) and their fit in an electrified industry. In the present work, recent progress made in electrochemical CO₂ capture is reviewed. The majority of these methods rely on the concept of “pH-swing” and the effect it has on the CO₂ hydration/dehydration equilibrium. Through a pH-swing, CO₂ can be captured and recovered by shifting the pH of a working fluid between acidic and basic pH. Such swing can be applied electrochemically through electrolysis, bipolar membrane electrodialysis, reversible redox reactions and capacitive deionization. In this review, we summarize main parameters governing these electrochemical pH-swing processes and put the concept in the framework of available worldwide capture technologies. We analyse the energy efficiency and consumption of such systems, and provide recommendations for further improvements. Although electrochemical CO₂ capture technologies are rather costly compared to the amine based capture, they can be particularly interesting if more affordable renewable electricity and materials (e.g., electrode and membranes) become widely available. Furthermore, electrochemical methods have the ability to (directly) convert the captured CO₂ to value added chemicals and fuels, and hence prepare for a fully electrified circular carbon economy.