Multishelled CaO Microspheres Stabilized by Atomic Layer Deposition of Al 2 O 3 for Enhanced CO 2 Capture Performance

CO 2 capture and storage is a promising concept to reduce anthropogenic CO 2 emissions. The most established technology for capturing CO 2 relies on amine scrubbing that is, however, associated with high costs. Technoeconomic studies show that using CaO as a high‐temperature CO 2 sorbent can significantly reduce the costs of CO 2 capture. A serious disadvantage of CaO derived from earth‐abundant precursors, e.g., limestone, is the rapid, sintering‐induced decay of its cyclic CO 2 uptake. Here, a template‐assisted hydrothermal approach to develop CaO‐based sorbents exhibiting a very high and cyclically stable CO 2 uptake is exploited. The morphological characteristics of these sorbents, i.e., a porous shell comprised of CaO nanoparticles coated by a thin layer of Al 2 O 3 (<3 nm) containing a central void, ensure (i) minimal diffusion limitations, (ii) space to accompany the substantial volumetric changes during CO 2 capture and release, and (iii) a minimal quantity of Al 2 O 3 for structural stabilization, thus maximizing the fraction of CO 2 ‐capture‐active CaO.