Low pressure reversibly driving colossal barocaloric effect in two-dimensional vdW alkylammonium halides
Yihong Gao, Donghui Wang, Fengxia Hu, Q. Huang, Youting Song, Shuaikang Yuan, Zheng-Ying Tian, Bingjie Wang, Zibing Yu, Houbo Zhou, Yue Kan, Yuan Lin, Jing Wang, Yunliang Li, Ying Liu, Yunzhong Chen, Jirong Sun, Tongyun Zhao, Baogen Shen
Abstract
Abstract Plastic crystals as barocaloric materials exhibit the large entropy change rivalling freon, however, the limited pressure-sensitivity and large hysteresis of phase transition hinder the colossal barocaloric effect accomplished reversibly at low pressure. Here we report reversible colossal barocaloric effect at low pressure in two-dimensional van-der-Waals alkylammonium halides. Via introducing long carbon chains in ammonium halide plastic crystals, two-dimensional structure forms in (CH 3 –(CH 2 ) n-1 ) 2 NH 2 X (X: halogen element) with weak interlayer van-der-Waals force, which dictates interlayer expansion as large as 13% and consequently volume change as much as 12% during phase transition. Such anisotropic expansion provides sufficient space for carbon chains to undergo dramatic conformation disordering, which induces colossal entropy change with large pressure-sensitivity and small hysteresis. The record reversible colossal barocaloric effect with entropy change ΔS r ~ 400 J kg −1 K −1 at 0.08 GPa and adiabatic temperature change ΔT r ~ 11 K at 0.1 GPa highlights the design of novel barocaloric materials by engineering the dimensionality of plastic crystals.