Achieving carbon neutrality requires the development of energy- and material-efficient pathways to capture and convert CO₂ emissions from dilute sources such as air or flue gas. Post-capture, a pure stream of CO₂ can be generated for geological storage, or reuse. To this end, the use of Ca- and Mg- oxides/hydroxides as sorbents for CO₂ capture has attracted significant attention due to several factors such as low cost, scalability, and ease of integration with cement manufacturing. However, the high thermal requirements and sintering associated degradation for the regeneration of Ca- and Mg- oxides/hydroxides from their respective carbonates remains a practical challenge. Herein, we discuss an ambient temperature electrochemical alternative that utilizes a pH gradient across a three-chamber cell to produce high purity CO₂ while regenerating Ca(OH)₂/Mg(OH)₂ from their respective carbonates and co-producing H₂ and O₂. More specifically, the kinetics, efficiencies and rate limiting steps involved with electrochemical sorbent generation is discussed. It was found that enhanced proton-particle contact led to charge efficiencies as high as 95%. Higher yields of Mg(OH)₂ are observed compared to that for Ca(OH)₂ during sorbent regeneration due to the lower solubility of Mg(OH)₂. To enhance the kinetics of CO₂ dissolution from ultra dilute sources, the role of regenerable solvents such as NaOH, Na-Glycinate and Na-Argininate for CO₂ fixation in the form of calcium carbonate or hydrated magnesium carbonate was also evaluated at temperatures below 60 ^oC. These findings represent a promising pathway for closing material and carbon cycles to advance a sustainable climate, energy, and environmental future.

Christopher Noe

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