Enhanced reversible barocaloric effect at low pressure in neopentyl plastic crystal solid solutions

Abstract

The discovery of colossal barocaloric effects in neopentyl glycol (NPG) makes plastic crystals promising candidates for solid-state refrigerants with lower environmental impact than vapour compression fluids. Optimising operational temperatures and low-pressure operability remains challenging without compromising thermodynamic parameters. Here, we implement a strategy to improve the viability of NPG derivatives as barocaloric refrigerants. We blend pentaglycerine (PG) with NPG to lower the phase transition temperature, then dope the blend with 2% pentaerythritol (PE) to improve transition reversibility. In comparison with NPG under the same conditions, this ternary system has a seven-fold increase in reversible isothermal entropy change ( ¿=¿13.4¿J¿kg-1 K-1) and twenty-fold increase in operational temperature span ( ¿=¿18¿K) at pressures of 1 kbar. Synchrotron x-ray diffraction and quasielastic neutron scattering reveal structural and dynamical effects that broaden the temperature range of the first-order phase transition due to intermolecular hydrogen bond network disruption by the molecular dopants. We propose that exploiting the compositional phase space of multi-component molecular blends is effective for designing practicable molecular BCs.

This work was financially supported by an EPSRC grant (EP/V042262/1), a Carnegie Research Incentive Grant (RIG013328) and SGR-00343 Project (Catalonia), by grant PID2023-146623NB-I00 funded by MICIU and by ERDF/EU and is part of Maria de Maeztu Units of Excellence Programme CEX2023-001300-M funded by MCIN/AEI (10.13039/501100011033). We acknowledge an EPSRC strategic equipment funding grant (EP/X030083/1).

Peer Reviewed

Postprint (published version)