Version 2 2024-01-18, 14:21Version 2 2024-01-18, 14:21
Version 1 2024-01-16, 19:36Version 1 2024-01-16, 19:36
journal contribution
posted on 2024-01-18, 14:21authored byJinyoung Seo, Rahil Ukani, Juanjuan Zheng, Jason D. Braun, Sicheng Wang, Faith E. Chen, Hong Ki Kim, Selena Zhang, Catherine Thai, Ryan D. McGillicuddy, Hao Yan, Joost J. Vlassak, Jarad A. Mason
Barocaloric effectssolid-state
thermal changes
induced
by the application and removal of hydrostatic pressureoffer
the potential for energy-efficient heating and cooling without relying
on volatile refrigerants. Here, we report that dialkylammonium halidesorganic
salts featuring bilayers of alkyl chains templated through hydrogen
bonds to halide anionsdisplay large, reversible, and tunable
barocaloric effects near ambient temperature. The conformational flexibility
and soft nature of the weakly confined hydrocarbons give rise to order–disorder
phase transitions in the solid state that are associated with substantial
entropy changes (>200 J kg–1 K–1) and high sensitivity to pressure (>24 K kbar–1), the combination of which drives strong barocaloric effects at
relatively low pressures. Through high-pressure calorimetry, X-ray
diffraction, and Raman spectroscopy, we investigate the structural
factors that influence pressure-induced phase transitions of select
dialkylammonium halides and evaluate the magnitude and reversibility
of their barocaloric effects. Furthermore, we characterize the cyclability
of thin-film samples under aggressive conditions (heating rate of
3500 K s–1 and over 11,000 cycles) using nanocalorimetry.
Taken together, these results establish dialkylammonium halides as
a promising class of pressure-responsive thermal materials.