Of Glasses and Crystals: Mitigating the Deactivation of CaO-Based CO(2) Sorbents through Calcium Aluminosilicates

[Image: see text] CaO-based sorbents are cost-efficient materials for high-temperature CO(2) capture, yet they rapidly deactivate over carbonation-regeneration cycles due to sintering, hindering their utilization at the industrial scale. Morphological stabilizers such as Al(2)O(3) or SiO(2) (e.g., introduced via impregnation) can improve sintering resistance, but the sorbents still deactivate through the formation of mixed oxide phases and phase segregation, rendering the stabilization inefficient. Here, we introduce a strategy to mitigate these deactivation mechanisms by applying (Al,Si)O(x) overcoats via atomic layer deposition onto CaCO(3) nanoparticles and benchmark the CO(2) uptake of the resulting sorbent after 10 carbonation-regeneration cycles against sorbents with optimized overcoats of only alumina/silica (+25%) and unstabilized CaCO(3) nanoparticles (+55%). (27)Al and (29)Si NMR studies reveal that the improved CO(2) uptake and structural stability of sorbents with (Al,Si)O(x) overcoats is linked to the formation of glassy calcium aluminosilicate phases (Ca,Al,Si)O(x) that prevent sintering and phase segregation, probably due to a slower self-diffusion of cations in the glassy phases, reducing in turn the formation of CO(2) capture-inactive Ca-containing mixed oxides. This strategy provides a roadmap for the design of more efficient CaO-based sorbents using glassy stabilizers.