Pressure-freezing of dodecane: exploring the crystal structures, formation kinetics and phase diagrams for colossal barocaloric effects in n -alkanes

Barocaloric (BC) materials provide cheaper and more energy efficient alternatives to traditional refrigerants. Some liquid alkanes were recently shown to exhibit a colossal BC effect, matching the entropy changes in commercial vapour–liquid refrigerants. Dodecane was predicted to have the largest en...

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Bibliographic Details
Published in:RSC advances 2023-11, Vol.13 (47), p.33305-33317
Main Authors: Poręba, Tomasz, Kicior, Inga
Format: Article
Language:English
Subjects:
Alkanes
Alternative energy sources
Chemistry
Crystal growth
Crystal lattices
Crystal structure
Crystallization
Diamond anvil cells
Dodecane
Entropy
Freezing
Kinetics
Lattice energy
Phase diagrams
Pressure dependence
Raman spectroscopy
Refrigerants
Room temperature
Single crystals
Synchrotrons
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Summary:Barocaloric (BC) materials provide cheaper and more energy efficient alternatives to traditional refrigerants. Some liquid alkanes were recently shown to exhibit a colossal BC effect, matching the entropy changes in commercial vapour–liquid refrigerants. Dodecane was predicted to have the largest entropy change among the studied alkanes. Using synchrotron powder and single-crystal X-ray diffraction, Raman spectroscopy, and lattice energy calculations, we investigated the BC effects of n -dodecane at high pressures and room temperature. Remarkably, a colossal entropy change |Δ S | of 778 J kg −1 K −1 at 0.15(3) GPa and 295 K was observed. Spectroscopic studies revealed that this entropy change correlates closely with the conformational transition from mixed gauche to all- trans forms during pressure-induced crystallization. Additionally, the usage of a diamond anvil cell allowed the determination of the crystal structures of in situ crystallized n -un- and dodecane, as well as evaluation of the pressure-dependent crystal growth kinetics. Furthermore, our research suggests that the entropy change (per kilogram) upon compression should be similar for all n -alkanes within the range of 9–18 carbon atoms in the molecule, based on their lattice energies. Even-numbered alkanes are predicted to exhibit superior BC properties compared to their odd-numbered counterparts due to the more symmetric crystal structures and lower propensity to form plastic phases with lower transition entropy.
ISSN:2046-2069
2046-2069
DOI:10.1039/d3ra06957e