Mechanistic Understanding of CaO-Based Sorbents for High-Temperature CO2 Capture: Advanced Characterization and Prospects.

Carbon dioxide capture and storage technologies are short to mid-term solutions to reduce anthropogenic CO2 emissions. CaO-based sorbents have emerged as a viable class of cost-efficient CO2 sorbents for high temperature applications. Yet, CaO-based sorbents are prone to deactivation over repeated CO2 capture and regeneration cycles. Various strategies have been proposed to improve their cyclic stability and rate of CO2 uptake including the addition of promoters and stabilizers (e. g., alkali metal salts and metal oxides), as well as nano-structuring approaches. However, our fundamental understanding of the underlying mechanisms through which promoters or stabilizers affect the performance of the sorbents is limited. With the recent application of advanced characterization techniques, new insight into the structural and morphological changes that occur during CO2 uptake and regeneration has been obtained. This review summarizes recent advances that have improved our mechanistic understanding of CaO-based CO2 sorbents with and without the addition of stabilizers and/or promoters, with a specific emphasis on the application of advanced characterization techniques.