High-performance CaO-based composites synthesized using a space-confined chemical vapor deposition strategy for thermochemical energy storage

The Calcium-Looping (CaL) process, based on the reversible carbonation/calcination of CaO, is a promising technology for thermochemical energy storage (TCES) in Concentrated Solar Power (CSP) plants. However, the major drawback of this technology is the rapid deactivation of CaO due to sintering. In this work, we have synthesized CaO-based, inert oxide-stabilized composites through a space-confined chemical vapor deposition process. Different synthesis parameters such as the inert material (Al 2 O 3 , SiO 2 or TiO 2 ) used as the stabilizer and the CaO concentration in the sorbent were investigated. Among the three different promoters used to increase the resistance of CaO toward sintering, Al 2 O 3 resulted in the most stable composites. The composite with only 5 mol.% Al showed an excellent CO 2 uptake capacity, 0.59 g CO 2 /g composite, over 50 cycles without any deactivation. Based on the calculation, this composite maintained an energy density of 1.50 GJ/t after 50 cycles, corresponding to 87% of the theoretical maximum. This high stability is attributed to the unique synthetic strategy in which the thermally stable oxide nanoparticles deposited on the surface of CaO crystalline grain and prevented its aggregation and overgrowth.