摘要
This study presents a dual-fluid atomization spray pyrolysis (SP) synthesis to fabricate porous hollow spherical CaO heat carriers for thermochemical energy storage. Key preparation conditions, including solution concentration, molar ratio of citric acid to Ca 2+ (CA/Ca 2+ ratio), and pyrolysis temperature were systematically analyzed for their effects on cyclic energy storage/release performance, particle size, micromorphology, crystallite size and pore structure via simultaneous thermal analyzer (STA), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and N 2 isothermal adsorption-desorption methods. Results indicate that higher solution concentrations and CA/Ca 2+ ratios increased particle size and promoted surface grains coalescence. Concentration ≥2 mol∙L −1 or CA/Ca 2+ ratio ≤0.5:1 degraded cyclic performance, and the optimal values are 1 mol∙L −1 and 1:1. Pyrolysis temperature significantly influenced the microstructure by influencing the pyrolysis mechanism: At 400 °C, spray drying dominated, forming hollow spheres with uncoalesced surface grains. At 500–600 °C, mesoporous structure formed with enhanced grain coalescence. At 700–800 °C, violent pyrolysis produced irregular, macroporous particles with high initial but rapidly declining performance. The optimal temperature at 600 °C yielded CaO heat carriers with a high specific surface area of 33.24 m 2 ∙g −1 , achieving 92.8 % initial carbonation conversion and a 30-cycle accumulative energy storage density of 46.13 kJ∙g −1 , which is 2.33 times higher than commercial CaO. Correlation analysis identified the specific surface area, total pore volume, and mesoporous volume fraction as key factors influencing post-cycling carbonation conversion and accumulated energy storage density. This work demonstrates SP synthesis as a scalable approach to tailor CaO microsphere for enhanced thermochemical energy storage.
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