Microtubule-structured, dolomite-derived CO2 sorbents synthesized by impregnated layer solution combustion for direct solar-driven calcium looping

Microtubule-structured, Mn/Fe binary-doped dolomite-derived sorbents were synthesized by impregnated layer combustion synthesis method for direct solar-driven calcium looping system. The temperatures at which combustion occurs—specifically, 600, 700, 800, and 900 °C—as well as the modes used for impregnation, namely the wet and dry impregnated layer combustion synthesis methods, have a significant impact on both the CO 2 capture performance and the optical absorbance of the sorbent. Overall, the cyclic CO 2 capture performance of the microtubule-structured sorbents has been significantly enhanced, with a mere loss of 0.10 % to 0.32 % in CO 2 capture capacity after 20 cycles, attributed to the distinctive porous structure of the absorbent paper. Moreover, the combustion synthesis temperature exceeds a certain threshold, it will compromise the integrity of the hollow microstructure of the sorbent, and 800 °C is the desirable synthesis combustion temperature. The average solar absorbance of the sorbent significantly improves under various impregnation modes at 800 °C, reaching 66 % to 69 %. This enhancement is attributed to the formation of Ca 2 Fe 2 O 5 and Ca 2 MnO 4 , along with the decomposition of CaCO 3 . It’s noteworthy that the citric acid complexed microtubule-structured, dolomite-derived sorbent exhibits the highest and most consistent CO 2 capture capacity, retaining 93.5 % of its initial CO 2 capture capacity (0.243 g/g) by the 20th cycle. It alongside possesses the highest average solar absorbance of 69 %, underscoring the efficacy of citric acid complexes in achieving atomic-level uniformity.