Effects of Oxygen-Vacancy-Promoted Ion Diffusion on CO2 Capture Behavior of CaO-Based Sorbents

Current studies on the modification of CaO-based sorbents have paid less attention to ion migration resistance within the product layer of CaCO3 during carbonation. In this work, limestone-derived sorbents with enhanced carbonation reactivity and diffusivity due to the incorporation of Na+ ions into the CaO lattice were prepared by a hydrated ion adsorption method. The Na+-ion-modified sorbents exhibited better CO2 capture capacity and durability. After 30 cycles, Na/Ca-0.10 sorbents still maintained a larger carbonation conversion (49.5%), which was 147.5% higher than that of the unmodified CaCO3 precursor. It was demonstrated that solid-state ion transport channels resulting from the existence of oxygen vacancy were constructed in the product layer of modified sorbents, producing a distinct three-stage mechanism (reaction–coupling–diffusion) during the carbonation process. As a result, the prepared CaO-based sorbents could maintain a higher reactivity after the formation of the product layer of CaCO3 and the sintering over iterated looping.