Abstract:Barocaloric effects in a layered hybrid organic-inorganic compound, (C 10 H 21 NH 3 ) 2 MnCl 4 , that are reversible and colossal under pressure changes below 0.1 GPa are reported. This barocaloric performance originates in a phase transition characterized by different features: A strong disordering of the organic chains, a very large volume change, a very large sensitivity of the transition temperature to pressure and a small hysteresis. The obtained values are unprecedented among solid-state cooling material… Show more
“…Moreover, since the inorganic layers and organic bilayers of 2-D perovskites can be independently manipulated, we further expected that phase transition hysteresis could be minimized through confinement effects and careful control of the organic–inorganic interfaces. We note that 2-D perovskites were also independently identified as promising barocaloric materials by Lloveras and coworkers while our work was under peer review 25 . Fig.…”
Pressure-induced thermal changes in solids—barocaloric effects—can be used to drive cooling cycles that offer a promising alternative to traditional vapor-compression technologies. Efficient barocaloric cooling requires materials that undergo reversible phase transitions with large entropy changes, high sensitivity to hydrostatic pressure, and minimal hysteresis, the combination of which has been challenging to achieve in existing barocaloric materials. Here, we report a new mechanism for achieving colossal barocaloric effects that leverages the large volume and conformational entropy changes of hydrocarbon order–disorder transitions within the organic bilayers of select two-dimensional metal–halide perovskites. Significantly, we show how the confined nature of these order–disorder phase transitions and the synthetic tunability of layered perovskites can be leveraged to reduce phase transition hysteresis through careful control over the inorganic–organic interface. The combination of ultralow hysteresis and high pressure sensitivity leads to colossal reversible isothermal entropy changes (>200 J kg−1 K−1) at record-low pressures (<300 bar).
“…Moreover, since the inorganic layers and organic bilayers of 2-D perovskites can be independently manipulated, we further expected that phase transition hysteresis could be minimized through confinement effects and careful control of the organic–inorganic interfaces. We note that 2-D perovskites were also independently identified as promising barocaloric materials by Lloveras and coworkers while our work was under peer review 25 . Fig.…”
Pressure-induced thermal changes in solids—barocaloric effects—can be used to drive cooling cycles that offer a promising alternative to traditional vapor-compression technologies. Efficient barocaloric cooling requires materials that undergo reversible phase transitions with large entropy changes, high sensitivity to hydrostatic pressure, and minimal hysteresis, the combination of which has been challenging to achieve in existing barocaloric materials. Here, we report a new mechanism for achieving colossal barocaloric effects that leverages the large volume and conformational entropy changes of hydrocarbon order–disorder transitions within the organic bilayers of select two-dimensional metal–halide perovskites. Significantly, we show how the confined nature of these order–disorder phase transitions and the synthetic tunability of layered perovskites can be leveraged to reduce phase transition hysteresis through careful control over the inorganic–organic interface. The combination of ultralow hysteresis and high pressure sensitivity leads to colossal reversible isothermal entropy changes (>200 J kg−1 K−1) at record-low pressures (<300 bar).
“…Therefore, the required pressure is in the range of commercial gas refrigerants for vapor-compression technologies (for instance, p (CO 2 ) ∼ 64 bar and p (R134a) ∼ 6 bar) 46 and is much lower than in the case of traditional solid barocalorics. 5 − 11 , 15 , 16 , 45 In view of these results, MIL-53(Al) shows a temperature span of, at least, 35 K for p = 16 bar, which widely exceeds the span of most barocaloric materials. 5 − 11 , 15 , 16 , 45 …”
Section: Resultsmentioning
confidence: 95%
“… 5 − 11 , 15 , 16 , 45 In view of these results, MIL-53(Al) shows a temperature span of, at least, 35 K for p = 16 bar, which widely exceeds the span of most barocaloric materials. 5 − 11 , 15 , 16 , 45 …”
Section: Resultsmentioning
confidence: 95%
“…In this context, to analyze the breathing-caloric effects for potential refrigeration applications, we calculate the caloric effect in terms of isothermal entropy change, which exhibits very large (colossal) values of up to Δ S ∼ 311.0 J K –1 kg –1 at 298 K. This pressure-induced breathing-caloric effect is very superior to most of the pressure-induced barocaloric effects reported in the literature. 5 − 11 , 15 , 16 , 45 Even more remarkably, the breathing-caloric effect is fully reversible under the application of very low pressures ( p = 16 bar,) in contrast to the p > 1000 bar required for most barocalorics. 5 − 11 Accordingly, the caloric strength of the material, defined as the isothermal entropy change per unit of pressure, Δ S /Δ p ∼ 19.4 × 10 3 J K –1 kg –1 kbar –1 , is the largest strength reported to date (see below).…”
Section: Resultsmentioning
confidence: 99%
“… (a) Ashby plot of Δ S vs p for MIL-53(Al) and different refrigerants. 5 − 11 , 15 , 16 , 45 , 46 (b) Comparison of the operating temperature range ( T span ) of the best refrigerants selected from (a). Note: In panel a, GAS = gas refrigerants, HOIMs = hybrid organic–inorganic materials, OPC = organic plastic crystals, SCO = spin crossover materials, POLY = polymers, AIS = ammonium inorganic salts, ISC = ionic superconductors.…”
In this work, “breathing-caloric”
effect is introduced
as a new term to define very large thermal changes that arise from
the combination of structural changes and gas adsorption processes
occurring during breathing transitions. In regard to cooling and heating
applications, this innovative caloric effect appears under very low
working pressures and in a wide operating temperature range. This
phenomenon, whose origin is analyzed in depth, is observed and reported
here for the first time in the porous hybrid organic–inorganic
MIL-53(Al) material. This MOF compound exhibits colossal thermal changes
of Δ
S
∼ 311 J K
–1
kg
–1
and Δ
H
∼ 93 kJ kg
–1
at room temperature (298 K) and under only 16 bar,
pressure which is similar to that of common gas refrigerants at the
same operating temperature (for instance,
p
(CO
2
) ∼ 64 bar and
p
(R134a) ∼ 6
bar) and noticeably lower than
p
> 1000 bar of
most
solid barocaloric materials. Furthermore, MIL-53(Al) can operate in
a very wide temperature range from 333 K down to 254 K, matching the
operating requirements of most HVAC systems. Therefore, these findings
offer new eco-friendly alternatives to the current refrigeration systems
that can be easily adapted to existing technologies and open the door
to the innovation of future cooling systems yet to be developed.
Solid‐state cooling exploits the thermal response of caloric materials when subjected to external physical fields and represents a promising alternative to conventional refrigeration technologies. However, existing caloric materials are often limited by relatively small caloric response and hysteresis issues rooted in first‐order structural transitions. Here, colossal and reversible elastocaloric effects near room temperature in superelastic graphene architectures are predicted by thermodynamic analysis and atomistic calculations. The estimated adiabatic temperature change can reach a value of 155 K under a compressive stress of 0.7 GPa in a wide temperature range of around 300 K, yielding outstanding elastocaloric strength and efficiency. More unique is that both cooling and warming can be realized in the materials by applying tensile and compressive strains to host conventional and inverse elastocaloric effects, respectively, with almost no fatigue behavior and hysteresis effect. Such unprecedented elastocaloric performance results from a strain‐induced large change in configurational entropy in the graphene architectures. These effects are potentially extendable to other superelastic nanomaterials and hence suggest new material settings for developing high‐performance solid‐state refrigerants.
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