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

Abstract

SBA-CaCl 2 (SCa) composites with high CaCl 2 content were prepared using the non-functionalized and the methyl-and carboxyl-functionalized mesoporous SBA-15 supports and their thermochemical heat storage (TCHS) performance have been investigated using a 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 CaCl 2 due to the well dispersion of salt 2 particles in the SBA pores. Non-functionalized composite demonstrated 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. Best performing non-functionalized composite exhibited stable heat storage capacity (317 ± 6 kJ.mol-1 CaCl2) and hydration rate (7 ± 0.15 × 10-5 s-1) for five successive hydration cycles at 30% relative humidity (RH).