Low pressure reversibly driving colossal barocaloric effect in two-dimensional vdW alkylammonium halides

• Published in: Nature communications 2024-02, Vol.15 (1), p.1838-1838, Article 1838
• Main Authors: Gao, Yi-Hong, Wang, Dong-Hui, Hu, Feng-Xia, Huang, Qing-Zhen, Song, You-Ting, Yuan, Shuai-Kang, Tian, Zheng-Ying, Wang, Bing-Jie, Yu, Zi-Bing, Zhou, Hou-Bo, Kan, Yue, Lin, Yuan, Wang, Jing, Li, Yun-liang, Liu, Ying, Chen, Yun-Zhong, Sun, Ji-Rong, Zhao, Tong-Yun, Shen, Bao-Gen
• Format: Article
• Language: English
• Subjects: 639/301/119/2795; 639/766/119/2795; Adiabatic; Ammonium; Carbon; Conformation; Crystals; Entropy; Halides; Humanities and Social Sciences; Hysteresis; Interlayers; Low pressure; Molecular chains; Molecular conformation; multidisciplinary; Phase transitions; Plastics; Pressure; Pressure effects; Science; Science (multidisciplinary); Sensitivity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-46248-1

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. The authors report the colossal barocaloric effect driven reversibly by low pressure in two dimensional van-der-Waals alkylammonium halides, underlyingly from the disordering of the organic alkyl chains within the two-dimensional structure.