Fourier-Transform Infrared Analysis of the Dehydration Mechanism of Mg(OH) 2 and Chemically Modified Mg(OH) 2

作者：Ryo Kurosawa, Masato Takeuchi, Junichi Ryu · 发表于：The Journal of Physical Chemistry C · 年份：2021 · DOI：10.1021/acs.jpcc.0c08696 · 被引用次数：44 · 研究领域：Adsorption and Cooling Systems、Phase Change Materials Research、Thermal Expansion and Ionic Conductivity

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 .