New two-component water sorbent CaCl2-FeKIL2 for solar thermal energy storage

A new two-component (composite) water sorbent CaCl2-FeKIL2 has been developed for sorption-based solar thermal energy storage. The matrix of the composite is FeKIL2 material with disordered mesopores, high surface area of 712 m2/g and mesopore dimensions between 4 and 29 nm. The composite, prepared by wet impregnation of FeKIL2 with CaCl2, has lower surface area (418 m2/g) and similar mesopore dimensions as the matrix. The maximum water sorption capacity of FeKIL2 is 0.21 g/g, while the composite possesses 3 times higher maximum water sorption capacity due to the presence of the salt in the matrix. Heat of adsorption of the composite is 50.4 kJ/mol. A short-term cycling test between temperatures of 150 and 40 °C at a water vapour pressure of 5.6 kPa confirms a comparatively good hydrothermal stability of the composite.

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► Mesoporous composite CaCl2-FeKIL2 was prepared for solar thermal energy storage.
► CaCl2 is an active component, which has been dispersed in FeKIL2 mesopores.
► CaCl2 increases maximum water sorption capacity of the composite.
► FeKIL2 matrix prevents CaCl2 leaching from the mesopores.
► Hydrothermal stability (20 cycles, 40–150 °C, 5.6 kPa) is reported for the first time.