Influence of Silica Functionalization on Water Sorption and Thermochemical Heat Storage of Mesoporous SBA-15/CaCl₂ Composites

SBA-CaCl2 (SCa) composites with high CaCl2 content were prepared using nonfunctionalized and methyl- and carboxyl-functionalized mesoporous SBA-15 supports, and their thermochemical heat storage (TCHS) performances have been investigated using a thermogravimetric/differential scanning calorimetry (TG/DSC) system coupled with a humidity generator. This paper presents the influence of silica (SBA-15) functionalization on the structural–textural properties of SCa composites and consequently on their water sorption and heat storage performances. All SCa composites exhibited enhanced water uptake compared to the pure CaCl2 due to the good dispersion of salt particles in the SBA pores. The nonfunctionalized composite demonstrated the highest water sorption rate and heat storage capacity compared to all functionalized composites. The Fickian rate constant (k) and conversion rate (dα/dt) determined for the hydration cycles revealed that the water sorption rate of the SCa composites is mainly controlled by the intrinsic reaction between the salt particles and water. The best performing nonfunctionalized composite exhibited a stable heat storage capacity (317 ± 6 kJ mol–1CaCl2) and hydration rate (7 ± 0.15 × 10–5 s–1) for five successive hydration cycles at 30% relative humidity (RH).