Remarkable low-temperature dehydration kinetics of rare-earth-ion-doped Ca(OH)2 for thermochemical energy storage

Thermochemical energy storage based on dehydration-hydration of Ca(OH)2/CaO reversible reaction is considered a promising strategy to address the intermittency of solar thermal energy due to its extremely high storage density, possibility of seasonal heat storage, and low cost. However, conventionally-used Ca(OH)2 particles suffer from instabilities and poor multi-cycle performance at high temperature, which limits their applications. Here, we propose rare-earth-ion-doped Ca(OH)2 materials for thermochemical energy storage at reduced dehydration temperature through extensive DFT computational screening. Rare-earth elements, Sc, Y, La, Gd and Lu, -doped Ca(OH)2 exhibit lower decomposition barrier in comparison to the Ca(OH)2 without doping. The Sc-doped Ca(OH)2 shows the significantly reduced onset temperature of ∼326 °C, which is 50 °C lower than that of the pure Ca(OH)2. Importantly, more than 3-fold increase in the dehydration rate and excellent stability during multi-cycles of the compositions at 320 °C is reached by the doping of Sc or Y into Ca(OH)2. The working performance makes this material a practical alternative to realize stable high-density solar thermal energy storage.