Barocaloric materials function through reversible structural transitions triggered by pressure changes, making them ideal for next-generation refrigeration cycles. Among these, plastic crystals have garnered significant attention due to their pronounced barocaloric response near ambient temperatures. These materials undergo transformations between disordered (plastic crystal) and ordered crystalline phases, with the associated entropy changes dictating their thermal energy exchange capabilities. However, harnessing these caloric changes efficiently for practical applications is complicated by thermal hysteresis, which limits the reversible fraction of the entropy change achievable within operable pressures.

A multinational research effort led by institutions including the University of Glasgow and the University of Cambridge has unveiled a strategic compositional engineering approach that markedly enhances the reversible barocaloric effect in neopentyl glycol (NPG) plastic crystals. Pure NPG—renowned for its significant caloric response—has been hampered by a large thermal hysteresis, impairing its cyclic cooling reliability. By blending NPG with pentaglycerine (PG) to form a binary solution, researchers first shifted the critical transition temperature closer to room temperature, improving its pragmatic usability.

The breakthrough came with the introduction of a minute 2 mol % addition of pentaerythritol (PE), creating a ternary solid solution—NPG:PG:PE in a 60:38:2 ratio. This alteration achieved a transformative increase in barocaloric reversibility and operational temperature window at achievable pressures around 1 kbar. Specifically, the ternary material exhibited a reversible entropy change of 13.4 J kg⁻¹ K⁻¹, a sevenfold enhancement compared to pristine NPG, and broadened its effective thermal range by approximately 18 K. Consequently, the reversible refrigeration capacity soared by over seventy times, positioning this material as a highly competitive candidate for sustainable cooling technology.

Importantly, this compositional tuning does not diminish the intrinsic heat absorption capacity; the material continues to transition through the requisite ordered to disordered phases with significant thermal energy exchange. Instead, the small PE fraction subtly modifies the molecular landscape, mitigating the energy barriers responsible for hysteresis during compression and decompression cycles. This refined molecular interaction enables smoother phase transformations, vital for real-world applications demanding reliability and efficiency.

To elucidate the microscopic mechanisms underpinning these macroscopic improvements, the research team leveraged quasielastic neutron scattering (QENS) techniques at the Institut Laue-Langevin’s IN16B spectrometer. QENS is uniquely capable of capturing molecular motions on picosecond to nanosecond timescales within hydrogen-rich solids, providing a window into the dynamic rotational and translational behaviors that govern phase transitions. By deploying inelastic fixed-window scans during controlled heating and cooling, the team correlated molecular dynamics directly with calorimetric hysteresis and structural phase data from diffraction studies.

The neutron scattering data revealed striking differences in the onset and progression of molecular reorientations across the order-disorder transition. In pure NPG, molecular motions appeared abruptly and exhibited pronounced asymmetry between heating and cooling, reflecting substantial thermal hysteresis. Conversely, the ternary NPG–PG–PE material demonstrated a more gradual and extended evolution of molecular dynamics with reduced directional discrepancy. This indicates that the inclusion of PE disrupts large hydrogen-bonded clusters found in the binary and pure materials, fostering a molecular environment more conducive to reversible transformations.

This fundamental insight highlights the critical influence of hydrogen bonding networks on the phase behavior and thermo-mechanical response of plastic crystals. The attenuation of these networks by minimal PE doping translates directly to lowered hysteresis and enhanced reversibility, showcasing how precise molecular design can tailor bulk material properties. Such understanding is essential for refining barocaloric materials, bridging the gap between promising physical phenomena and technologically viable cooling solutions.

Beyond advancing the frontier of barocaloric materials, this research exemplifies the power of combining compositional tuning with cutting-edge neutron spectroscopy to unravel complex molecular phenomena. These findings not only pave the way for more reliable, efficient, and environmentally benign refrigeration technologies but also establish guiding principles for molecular engineering across functional solid-state materials. As global cooling demand escalates alongside climate concerns, innovations like this will play a pivotal role in shaping sustainable cooling infrastructures.

Furthermore, the study’s implications extend to other caloric effects and stimuli-responsive materials, suggesting broad applicability of the molecular design strategies revealed. The ability to fine-tune phase transition dynamics and hysteresis behavior at the molecular level opens new horizons for solid-state thermal management and energy conversion technologies. As research continues, integrating these insights with device engineering will be critical to translating laboratory advancements into commercial refrigeration solutions.

In sum, the enhanced reversible barocaloric effect realized through subtle compositional control in neopentyl plastic crystals demonstrates a promising path forward for solid-state cooling technologies. Through meticulous molecular engineering and sophisticated neutron-scattering investigations, researchers have unlocked a significant advancement in balancing high cooling capacity with practical operational reversibility. This paradigm shift holds promise not only for reducing the environmental footprint of cooling but also for revolutionizing the way thermal energy is managed in various sectors, from food preservation to climate control.

Credit for this transformative research belongs to the collaborative efforts of the University of Glasgow, University of Cambridge, Universitat Politècnica de Catalunya, Diamond Light Source, and the Institut Laue-Langevin. Their combined expertise and innovative use of neutron spectroscopy have been instrumental in bringing these findings to light, illustrating the profound potential of interdisciplinary research strategies in materials science.

Subject of Research: Not applicable
Article Title: Enhanced reversible barocaloric effect at low pressure in neopentyl plastic crystal solid solutions
News Publication Date: 27-Jan-2026
Web References: 10.1038/s43246-026-01084-2
Image Credits: communications materials (2026)

Keywords

Materials science, Physics, Energy transfer, Heat, Spectroscopy

The core principle behind thermogalvanic refrigeration lies in its ability to exploit reversible electrochemical reactions to create an efficient cooling effect. Unlike conventional systems that consume substantial energy, this novel approach operates on a significantly reduced energy input, providing a sustainable alternative that aligns with global efforts to enhance energy efficiency. The researchers believe this technology could be adapted to a wide range of applications, including industrial cooling systems, wearable devices, and even household refrigerators.

Significant to thermogalvanic technology is the process’s ability to produce a cooling effect during a reversible chemical reaction rather than relying on thermodynamic cycles prevalent in standard refrigerators. When specific chemicals are utilized within these thermogalvanic cells, their interactions lead to an absorption of heat, thereby generating an effective cooling effect. As the research team elaborated, they have managed to markedly enhance the cooling capacity of these systems through innovative reengineering of electrolytes.

Senior author Jiangjiang Duan underscored the significance of this breakthrough, noting that while previous research on thermogalvanic technology focused primarily on initial system designs, their latest advancements introduce a more systematic and universal design strategy. By optimizing the chemical components of the thermogalvanic electrolytes, the researchers achieved unprecedented cooling capacities, paving the way for practical applications in commercial settings.

Moreover, the advanced cooling process operates on electrochemical redox reactions involving iron ions, which play a crucial role in the energy conversion that drives the refrigeration effect. By meticulously controlling the interactions of these ions during the electrochemical processes, the research team succeeded in maximizing the energy efficiency of their system. The two-phase reactions produce significant thermal changes, allowing the system to effectively cool the surrounding electrolyte solution.

Remarkably, the researchers reported a cooling performance that accounted for a temperature drop of 1.42 K. This represents a substantial improvement over previously established thermogalvanic systems, which typically demonstrated a cooling capacity of merely 0.1 K. This advancement not only showcases the innovative nature of their work but also illustrates the promising potential of thermogalvanic technology in advancing energy-efficient refrigeration solutions.

To achieve this leap in cooling performance, the researchers carefully selected electrolyte compositions that support enhanced ions’ behavior. By exploring various combinations of solutes and solvents, they concluded that utilizing hydrated iron salts mixed with perchlorate within a nitrile solvent resulted in a markedly improved cooling effect. This novel configuration allowed for increased mobility of iron ions, thereby optimizing the electrochemical reactions crucial for effective refrigeration.

Looking toward the future, Duan’s team is also focused on exploring new experimental designs and materials that could further enhance the cooling performance of their thermogalvanic systems. They are already in discussions to collaborate with industrial partners to facilitate the commercialization of this innovative refrigeration technology. The team hopes to refine the scalability, stability, and overall system-level design of their invention to ensure successful practical implementation in real-world applications.

The research has generated excitement not only within scientific circles but also among commercial stakeholders who recognize the potential for thermogalvanic refrigeration solutions to transform the industry. As the team continues its quest to improve and adapt their systems, the integration of thermogalvanic technology into broader applications remains a tantalizing prospect, signaling a new frontier in sustainable energy research.

Researchers are optimistic that as they continue advancing their experimental systems, the viability of thermogalvanic refrigeration will prove increasingly feasible for everyday use, signaling a shift towards energy-efficient technologies that benefit both consumers and our environment. The pathway paved by this study will undoubtedly inspire further innovations in energy conservation and pollution reduction in refrigeration technologies.

In summary, the work from the Huazhong University of Science and Technology is a landmark achievement in the field of electrochemical refrigeration. The ability to harness thermogalvanic processes not only opens new avenues for highly efficient cooling solutions but also serves as an illustration of the endless possibilities that arise when scientific inquiry aligns with the pressing need for sustainable technology. The research has laid a strong foundation for further exploration and commercial interest, ensuring that the journey toward more efficient refrigeration systems is just beginning.

Subject of Research: Thermogalvanic electrolytes for electrochemical refrigeration
Article Title: Solvation entropy engineering of thermogalvanic electrolytes for efficient electrochemical refrigeration
News Publication Date: January 30, 2025
Web References: Joule journal
References: Zeng et al. "Solvation entropy engineering of thermogalvanic electrolytes for efficient electrochemical refrigeration," Joule.
Image Credits: Yilin Zeng

Keywords

Sustainable energy, Electrolytes, Electrochemical reactions, Energy efficiency, Refrigeration technology, Thermogalvanic cooling, Renewable energy solutions, Environmental impact.