R. Kurosawa, M. Takeuchi and J. Ryu, J. Phys. Chem. C, 125, 5559-5571 (2021).
Mg(OH)2 is a medium-temperature chemical heat storage material. The addition of LiCl and/or LiOH to Mg(OH)2 has been reported to promote the dehydration of Mg(OH)2. However, the mechanism underlying the effect of the addition of Li compounds on the dehydration of Mg (OH)2 has not yet been elucidated. This study focused on the dehydration of pure Mg(OH)2 and Mg(OH)2 with added LiCl and/or LiOH. We analyzed the role of the Li compounds in the dehydration of Mg(OH)2 using X-ray diffraction and Fourier-transform infrared (FT-IR) spectroscopy. Our FT-IR measurements assigned the peaks of the bulk OH groups of Mg(OH)2, which are not referred to in previous studies. FT-IR measurements revealed that the surface state of Mg(OH)2 with added LiOH with a Mg(OH)2:LiOH mole rate of 100:20 was similar to that of MgO. This indicated that the addition of LiOH to Mg(OH)2 affected the dehydration of the Mg(OH)2 surface. Moreover, we confirmed that LiCl affected the dehydration of the bulk Mg(OH)2 phase. Using these results, we proposed possible mechanisms for the effects of the addition of LiCl and/or LiOH on the dehydration of Mg(OH)2. Lastly, we discuss the reason for the Li compounds promoting the dehydration of Mg(OH)2.