Revolutionizing Cooling: Extreme Barocaloric Effect in NH4SCN Aqueous Solutions Heralds a Sustainable Refrigeration Era
As the world’s demand for refrigeration escalates, driven by population growth and technological advances, the environmental costs of traditional vapor-compression refrigeration technologies grow ever more concerning. Conventional systems predominantly employ fluorocarbon-based refrigerants, which contribute significantly to global warming due to their high global warming potential. In recent years, efforts to find viable, environmentally friendly alternatives have gained momentum, yet many existing solid-state caloric materials, though promising, have faced limitations related to cooling capacity and inefficient heat transfer mechanisms.
A groundbreaking development by Zhang, Liu, Gao, and colleagues, published in Nature, introduces an entirely new paradigm: harnessing an extreme barocaloric effect arising directly from pressure-induced dissolution and precipitation phenomena in ammonium thiocyanate (NH4SCN) aqueous solutions. This now unveiled thermodynamic mechanism bypasses the limitations posed by conventional solid-state phase transitions, offering dramatic improvements in temperature change, cooling capacity, and energy efficiency.
The authors demonstrate that when external pressure is applied to an NH4SCN aqueous solution, it triggers a reversible dissolution-precipitation process. This dynamic phase behavior leads to an unprecedented temperature drop of up to 26.8 Kelvin at near-ambient conditions, a value that surpasses all previously reported caloric materials. This exceptional temperature modulation is attributed to the large entropy changes associated with solvation and crystallization, amplified by precise pressure tuning.
This pivotal insight into dissolution-driven barocaloric response challenges the longstanding focus on solid-solid phase transitions in caloric refrigeration research. Unlike traditional barocaloric, magnetocaloric, or electrocaloric materials requiring indirect heat exchange via secondary fluids, the aqueous nature of this solution facilitates direct heat transfer. The self-circulating liquid phase enhances thermal conductivity and system integration, circumventing inefficiencies that previously hindered practical adoption.
Through meticulous experimental characterization paired with theoretical modeling, the research team designed a Carnot-like refrigeration cycle operating between solubility-driven phase boundaries. The cycle achieves a cooling capacity of 67 Joules per gram per cycle, coupled with an impressive second-law efficiency of 77%, a substantial leap from efficiencies reported in solid-state caloric technologies. Such high efficiency is attributable to the large latent heat and minimal irreversible losses, suggesting immense potential for real-world refrigeration applications.
Beyond its technical merit, the NH4SCN aqueous system exemplifies sustainability. The key components are non-toxic, abundant, and pose minimal environmental risk compared to fluorocarbon refrigerants. The operational simplicity and scalability of this approach further enhance its attractiveness as a viable alternative for residential cooling, commercial refrigeration, and possibly industrial heat management.
The implications extend deeply into the refrigeration sector’s carbon footprint reduction strategies. By leveraging a chemically driven caloric effect, this solution offers a pathway to achieve durable, low-carbon refrigeration devices without reliance on complex magnetocaloric or electrocaloric materials, which often require rare or costly elements. Moreover, the liquid-state system’s fast response and reversibility enhance flexibility and control in temperature regulation.
While the discovery marks a significant milestone, the researchers acknowledge challenges remain. Optimal engineering of system components to harness the pressure-tuned phase transitions rapidly and reversibly will be critical. Additionally, long-term cycling stability and integration into existing cooling infrastructure warrant further investigation. Nevertheless, the fundamental breakthrough in exploiting dissolution-linked barocaloric effects is poised to spur renewed innovation.
Scientific communities are already exploring potential expansions of this principle to other salt solutions and chemistries. Preliminary data suggest that similar pressure-responsive solubility transitions in alternative aqueous or even organic systems could yield tailored caloric properties suited for diverse temperature ranges and cooling capacities. This versatility further broadens the horizons for caloric refrigeration deployment.
In sum, this study represents a transformative leap toward sustainable refrigeration technology grounded in fundamental chemistry and thermodynamics. Its combination of extreme barocaloric performance, environmental benignity, and operational efficiency embodies the core aspirations of next-generation cooling methods to meet global sustainability goals. As further research and development accelerate, widespread adoption could dramatically curtail the ecological impacts of global refrigeration.
This work not only signals a fresh frontier in caloric materials but also challenges researchers and industry to reconceptualize refrigeration beyond traditional frameworks. The pressure-mediated dissolution approach integrates the best facets of caloric and solution chemistry into a powerful and practical refrigeration modality. Its emergence could redefine standards for low-carbon cooling technologies across sectors worldwide.
As this pioneering avenue matures, it will be essential to foster interdisciplinary collaborations encompassing material science, chemical engineering, and environmental policy to ensure scalable, economically feasible technologies reach consumers broadly. The profound potential of extreme barocaloric effects at dissolution heralds an exciting era in refrigeration innovation, marrying cutting-edge science with urgent climate imperatives.
Ultimately, the discovery reported by Zhang et al. stands as a beacon of ingenuity, demonstrating that unlocking nature’s complex phase equilibria through applied pressure can yield revolutionary functional materials and processes. The journey from laboratory feasibility to commercial refrigeration realities holds promise to reshape how humanity cools its homes, preserves food, and powers industrial processes—sustainably and efficiently.
Subject of Research: Barocaloric refrigeration via pressure-tuned dissolution and precipitation in ammonium thiocyanate aqueous solutions.
Article Title: Extreme barocaloric effect at dissolution.
Article References:
Zhang, K., Liu, Y., Gao, Y. et al. Extreme barocaloric effect at dissolution. Nature (2026). https://doi.org/10.1038/s41586-025-10013-1
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41586-025-10013-1
Keywords: barocaloric effect, sustainable refrigeration, ammonium thiocyanate, dissolution precipitation, caloric materials, pressure-tuned phase transitions, cooling capacity, energy efficiency
