Synergistic enhancement of Ca-based materials via CeO2 and Al2O3 co-doping for enhanced CO2 capture and thermochemical energy storage in calcium looping technology

Calcium looping (CaL) technology, based on carbonation/calcination reactions, shows significant potential for both thermochemical energy storage (TCES) and CO2 capture. However, the reactivity of Ca-based materials decreases rapidly over multiple cycles. Herein a dual-stabilization strategy was adopted to address this issue by simultaneously incorporating CeO2 and Al2O3 into Ca-based materials. Their TCES characteristics and CO2 capture were then assessed via a dual packed-bed reactor. Results showed the optimal mass fraction of CeO2 and Al2O3 was 10 wt% for CO2 capture mode and 5 wt% for TCES mode. With the most effective mass fraction of CeO2 and Al2O3, the optimal CeO2/Al2O3 mass ratio ranged from 1:1 to 1:2 for CO2 capture mode and from 1:1 to 1:2.5 for TCES mode. In the tenth cycle, the effective conversion of co-doped materials, with a mass ratio of 1.67:3.33:95 for CeO2/Al2O3/CaO, reached 79 %, experiencing a 6 % reduction in initial reactivity. Comprehensive characterizations revealed that varying the CeO2/Al2O3 mass ratio enhanced the synergistic interactions between CeO2 and Al2O3. This variation improved the porosity of the Ca-based materials, facilitating the carbonation reaction. Additionally, this variation significantly enhanced the basicity of the materials, benefiting the carbonation reaction since CO2 is an acidic gas. The variation also increased the surface percentage of Ce3+, enriching oxygen vacancies and enhancing bulk oxygen migration to the surface, which favored the surface reaction between CO2 and O2-. All these factors contributed to the improved performance of the carbonation reaction.