Vapor Exchange Induced Particles-Based Sponge for Scalable and Efficient Daytime Radiative Cooling

Passive daytime radiative cooling technology (DRCT) has recently gained significant attention for its ability to achieve sub-ambient temperature without energy consumption, making it an attractive option for space cooling. The cooling performance can be further improved if radiative cooling materials also exhibit high thermal insulation performance. However, synthesizing radiative cooling materials that possess low thermal conductivity while maintaining mechanical durability remains a challenge. Here, a vapor exchange method is developed to prepare particles-based poly(vinylidene fluoride-co-hexafluoropropylene) sponge materials for scalable and efficient daytime radiative cooling. By tailoring the particle diameter distribution, high solar reflection (94.5%), high infrared emissivity (0.956), and low thermal conductivity (0.048 W m⁻¹ K⁻¹) are achieved, resulting in a sub-ambient cooling of 9.8 °C under direct solar irradiation. Additionally, the sponge material exhibits good mechanical durability, sustaining deformation with a strain up to 40%, making it adaptable to diverse scenarios. A radiative cooling material with mechanical durability and thermal insulation can thus pave the way for large-scale applications of DRCT.     

Thermo-Responsive Self-Ceramifiable Robust Aerogel with Exceptional Strengthening and Thermal Insulating Performance at Ultrahigh Temperatures

High-performance thermal insulating aerogels are attractive candidates for thermal protection in extreme environments. However, inorganic aerogels’ brittleness and poor machinability limit their applications, while organic aerogels suffer from severe strength degradation and structural collapse at high temperatures. Herein, for the first time, a thermo-responsive self-ceramifiable aerogel is demonstrated with exceptional strengthening and thermal insulation at high temperatures. This aerogel exhibits excellent toughness and processability like polymers under normal conditions but spontaneously transforms into high-strength semi-crystalline hard ceramics upon exposure to high temperatures. After prolonged thermal attack at 800 °C, the strength of the aerogels does not decrease but significantly increases several-fold (from 0.739 to 2.726 MPa). The self-ceramization behavior and mechanism of the aerogel are illustrated in detail. The unique self-ceramifiable capacity enables aerogels to provide fire resistance, high-strength support, and excellent thermal insulation at ultrahigh temperatures. Even with continuous burning at 1300 °C for 60 min, the 15 mm thick aerogel shows low backside temperature below 300 °C, crack-free overall structure, and invariant porous morphology. This self-ceramifiable aerogel opens up a new avenue for developing thermal-protection materials with toughness, machinability, high strength, and thermal insulation in extreme environments.     

Multifunctional Superelastic Cellulose Nanofibrils Aerogel by Dual Ice-Templating Assembly

A superelastic aerogel with fast shape recovery performance from large compressive strain is highly desired for numerous applications such as thermal insulation in clothing, high-sensitive sensors, and oil contaminant removal. Fabrication of superelastic cellulose nanofibrils (CNF) aerogels is challenging as the CNF can assemble into non-elastic sheet-like cell walls. Here, a dual ice-templating assembly (DITA) strategy is proposed that can control the assembly of CNF into sub-micrometer fibers by extremely low temperature freezing (–196 °C), which can further assemble into an elastic aerogel with interconnected sub-micron fibers by freezer freezing (−20 °C) and freeze drying. The CNF aerogel from the DITA process demonstrates isotropic superelastic behavior that can recover from over 80% compressive strain along both longitudinal and cross-sectional directions, even in an extremely cold liquid nitrogen environment. The elastic CNF aerogel can be easily modified by chemical vapor deposition of organosilane, demonstrating superhydrophobicity (164° water contact angle), high liquid absorption (489 g g⁻¹ of chloroform absorption capacity), self-cleaning, thermal insulating (0.023 W (mK)⁻¹), and infrared shielding properties. This new DITA strategy provides a facile design of superelastic aerogels from bio-based nanomaterials, and the derived high performance multifunctional elastic aerogel is expected to be useful for a wide-range of applications.     

Infrared-Reflective Transparent Hyperbolic Metamaterials for Use in Radiative Cooling Windows

Passive multilayer coatings for windows have potential to improve energy consumption for indoor temperature regulation. The coatings should block the solar IR energy (800–2500 nm) while maintaining visible light transparency (400–700 nm) to prevent unwanted heating of the interior of a building or a vehicle. It should also efficiently radiate thermal energy to prevent excessive heating. Although solar energy management and radiative cooling techniques have been investigated individually, the combination of the two, a transparent radiative cooler, has emerged only recently. This study theoretically and experimentally demonstrates a transparent radiative cooling window using a combination of planar hyperbolic metamaterials and a uniform layer of polydimethylsiloxane, resulting in high visible transparency (>60%), IR reflectivity (>89%), and thermal emissivity (>95%). Daytime temperature experiments confirm that the cooling window efficiently lowers the interior temperature by as much as 7 °C.     

“Stiff–Soft” Binary Synergistic Aerogels with Superflexibility and High Thermal Insulation Performance

Designing aerogel materials featuring both high thermal insulation property and excellent mechanical robustness is of great interest for applications in superior integrated energy management systems. To meet the above requirements, composite aerogels based on hierarchical “stiff–soft” binary networks are reported, in which secondary mesoporous polymethylsilsesquioxane domains intertwined by bacterial cellulose nanofibrillar networks are connected in tandem. The resulting composite aerogels are characterized by highly porous (93.6%) and nanosized structure with a surface area of 660 m² g^?1, leading to the excellent thermal insulation performance with a low thermal conductivity of 15.3 mW m^?1 K^?1. The integrated “stiff–soft” binary nature also endows the composite aerogels with high flexibility that can conform to various substrates as well as large tensile strength that can withstand more than 2.70 × 10⁴ times its own weight. These composite aerogels show multifunctionality in terms of efficient wearable protection, controllable thermal management, and ultrafast oil/water separation. These favorable multifeatures present composite aerogels ideal for aerospace, industrial, and commercial applications.     

Joule Heating Characteristics of Emulsion‐Templated Graphene Aerogels

The Joule heating properties of an ultralight nanocarbon aerogel are investigated with a view to potential applications as energy‐efficient, local gas heater, and other systems. Thermally reduced graphene oxide (rGO) aerogels (10 mg cm^?3) with defined shape are produced via emulsion‐templating. Relevant material properties, including thermal conductivity, electrical conductivity and porosity, are assessed. Repeatable Joule heating up to 200 °C at comparatively low voltages (≈1 V) and electrical power inputs (≈2.5 W cm^?3) is demonstrated. The steady‐state core and surface temperatures are measured, analyzed and compared to analogous two‐dimensional nanocarbon film heaters. The assessment of temperature uniformity suggests that heat losses are dominated by conductive and convective heat dissipation at the temperature range studied. The radial temperature gradient of an uninsulated, Joule‐heated sample is analyzed to estimate the aerogel's thermal conductivity (around 0.4 W m^?1 K^?1). Fast initial Joule heating kinetics and cooling rates (up to 10 K s^?1) are exploited for rapid and repeatable temperature cycling, important for potential applications as local gas heaters, in catalysis, and for regenerable of solid adsorbents. These principles may be relevant to wide range of nanocarbon networks and applications.     

Eco-Friendly Transparent Silk Fibroin Radiative Cooling Film for Thermal Management of Optoelectronics

Although transparent radiative cooling is a passive cooling strategy with practical applications and aesthetic appeal, complex manufacturing processes and the use of environmentally unfriendly thermal emitters remain latent problems. Herein, eco-friendly transparent silk radiative cooling (TSRC) films are developed, regenerated from natural silkworm cocoons, for zero-energy-consumption thermal management of optoelectronic devices. These TSRC films can dissipate heat radiatively through molecular vibrations of the protein backbone and side chains, while retaining the function and appearance of the associated devices, due to their high visible transparency. Theoretical and experimental investigations revealed that the thermal emission increases rapidly upon increasing the film thickness, but slowly thereafter achieves saturation; nevertheless, the intrinsic solar absorption of silk in the ultraviolet and near-infrared regions also grows linearly, unavoidably weakening the cooling effect. After spectroscopic optimization, the maximum cooling power during the daytime and nighttime is improved to 77.6 and 101.7 W m⁻², respectively. Gratifyingly, the films have a remarkable effect on the cooling performance of electronic devices under sunlight. For example, the TSRC film provides a temperature drop of 5.1 °C for a smartphone during multitasking and charging, and 14 °C for a silicon solar panel with an improvement in the photoelectronic conversion efficiency (≈7%).     

Dynamically Tunable Subambient Daytime Radiative Cooling Metafabric with Janus Wettability

Incorporating zero-energy-input cooling technology into personal thermal management (PTM) systems is a promising solution for preventing heat-related illnesses while reducing energy consumption. Although concepts for passive radiative cooling materials are proposed, achieving subambient cooling performance while providing good wearing comfort remains a challenge. Here, a moisture-wicking nonwoven metafabric is reported that assembles radiative cooling and evaporative heat dissipation to achieve high-performance thermal and moisture comfort management. This metafabric demonstrates excellent spectral-selectivity (sunlight reflection of ≈92%, atmospheric window thermal emissivity of ≈97%) and Janus wettability through large-scale electrospinning and hierarchical design, and also inherits superior elasticity, air/moisture permeability of nonwoven fabric. Subambient temperature drops of ≈6.5 °C (≈750 W m⁻² solar intensity) for stand-alone metafabric are observed. Thanks to the moisture-wicking effect (water evaporation rate of 0.31 g h⁻¹ and water transport index of 1220%) of metafabric that enables fast evaporation of sweat, a maximum generation of 1 mL h⁻¹ of sweat can cool the skin, thus reducing the excessive sweating risk after intense exercise. Additionally, the cooling performance of metafabric can be regulated by applying various strains (0–100%). The cost-efficiency and good wearability of metafabric provide an innovative way to sustainable energy, smart textiles, and thermal wet comfort applications.     

Efficient and Stable Flexible Organic Solar Cells via the Enhanced Optical-Thermal Radiative Transfer

Heating is a knotty factor contributing to device degradation of flexible organic solar cells (FOSCs), and thermal regulation plays a crucial role in the realization of long operational lifetime. Herein, a passive cooling strategy for stable FOSCs is proposed by boosting the optical-thermal radiative transfer to reduce the insufficient thermal dissipation and the elevated temperature caused by irradiation-induced heating, while retaining their flexibility and portability. A spectrally selective coupling structure consisting of subwavelength hemisphere pattern and distributed Bragg reflector is integrated into FOSCs to collectively enhance out-coupling of infrared radiation and limit near-infrared absorption-induced heat generation, leading to a reduced heat power intensity of 292.5 W cm⁻² and the decreased working temperature by 9.6 °C under outdoor sunlight irradiation. The D18:Y6:PC₇₁BM-based FOSCs achieve a power conversion efficiency of over 17% with a prolonged T₈₀ lifetime as long as one year under real outdoor working conditions. These results represent a new opportunity for enhancing the operational stability of FOSCs.     

Electrically Heatable Graphene Aerogels as Nanoparticle Supports in Adsorptive Desulfurization and High‐Pressure CO2 Capture

Reduced‐graphene‐oxide (rGO) aerogels provide highly stabilising, multifunctional, porous supports for hydrotalcite‐derived nanoparticles, such as MgAl‐mixed‐metal‐oxides (MgAl‐MMO), in two commercially important sorption applications. Aerogel‐supported MgAl‐MMO nanoparticles show remarkable enhancements in adsorptive desulfurization performance compared to unsupported nanoparticle powders, including substantial increases in organosulfur uptake capacity (>100% increase), sorption kinetics (>30‐fold), and nanoparticle regeneration stability (>3 times). Enhancements in organosulfur capacity are also observed for aerogel‐supported NiAl‐ and CuAl‐metal‐nanoparticles. Importantly, the electrical conductivity of the rGO aerogel network adds completely new functionality by enabling accurate and stable nanoparticle temperature control via direct electrical heating of the graphitic support. Support‐mediated resistive heating allows for thermal nanoparticle recycling at much faster heating rates (>700 °C?min^?1) and substantially reduced energy consumption, compared to conventional, external heating. For the first time, the CO₂ adsorption performance of MgAl‐MMO/rGO hybrid aerogels is assessed under elevated‐temperature and high‐CO₂‐pressure conditions relevant for pre‐combustion carbon capture and hydrogen generation technologies. The total CO₂ capacity of the aerogel‐supported MgAl‐MMO nanoparticles is more than double that of the unsupported nanoparticles and reaches 2.36 mmol·CO₂ g^?1 ads (at p_CO2 = 8 bar, T = 300 °C), outperforming other high‐pressure CO₂ adsorbents.     

Tailoring Aerogels and Related 3D Macroporous Monoliths for Interfacial Solar Vapor Generation

Interfacial solar vapor generation is emerging as a promising water treatment technology with high solar energy efficiency and minimized carbon footprint. Among various kinds of materials development, aerogels, with inherent high porosity, lightweight, enhanced absorption, and minimized thermal conductivity, are attracting significant attention for achieving high‐performance solar vapor generation. Herein, recent progress in tailoring aerogels (such as graphene [oxide], carbon nanotubes, and polymer aerogels) and related 3D macroporous architectures for interfacial solar vapor generation is presented. Furthermore, the challenges and opportunities associated with employing aerogels in solar vapor generation are also discussed.     

Visibly Clear Radiative Cooling Metamaterials for Enhanced Thermal Management in Solar Cells and Windows

The study of transparent daytime radiative cooling with no additional energy consumption is a promising area of research. Its applications include solar cells and building and automobile windows that are prone to heating issues. Ubiquitous applications necessitate the development of metamaterials with high mechanical flexibility in a scalable manner while overcoming translucence. In this study, visibly clear and flexible radiative cooling metamaterials have been developed using a newly designed optical modulator filled into randomly distributed silica aerogel microparticles in a silicone elastomer. The optical modulator effectively suppresses visible light scattering, thus enabling higher loading of silica aerogel microparticles while securing visible clarity. The significant suppression of the rise in temperature by the metamaterial is verified using both indoor and outdoor experiments. The visibly clear metamaterials deployed in solar cells and windows can effectively suppress the rise in temperature under solar irradiation, thereby mitigating the performance degradation of solar cells by heating issues and suppressing the rise in temperature of indoor air.     

A Promising Radiation Thermal Protection Coating Based on Lamellar Porous Ca-Cr co-Doped Y3NbO7 Ceramic

Dissipation of heat efficiently from a hot object via radiation while minimizing the inward heat conduction is the key requirement of radiation thermal protection. In this study, a Ca-Cr co-doped Y₃NbO₇ coating with lamellar porous structure is fabricated, which shows an ultra-low thermal conductivity (<0.7 W m⁻¹ K⁻¹) and near-unity emissivity (>0.9) across a broad wavelength range of ≈1–24 µm. This record high emissivity to thermal conductivity ratio (≈1.3) is experimentally and theoretically revealed from a multi-scale perspective. The diffusoin-mediated thermal conduction feature of niobates combined with lamellar porous structure of the coating reduces its thermal conductivity to an impressive 0.5 W m⁻¹ K⁻¹ at 25 °C, surpassing the theoretical amorphous limitation of 0.72 W m⁻¹ K⁻¹. Experiments and FDTD calculation results demonstrate that the intrinsic emissivity dips at shallow extinction wavelengths (1 and 8 µm) and strong phonon-polariton resonances wavelengths (>13 µm) can be effectively compensated by the multiple scattering/absorption and gradual modulation of conical shape/effective refractive index induced by surface micro-protrusion structures, respectively. Furthermore, the coating exhibits robust mechanical and thermal stability with a high bonding strength (18.3 MPa) and thermal expansion coefficient (≈11 × 10⁻⁶ K⁻¹ at 1200 °C) comparable to YSZ, showing great potential in the radiation thermal protection field.     

Superelastic and Ultralight Aerogel Assembled from Hemp Microfibers

Aerogels with both high elastic strain and fast shape recovery after compression have broad application potentials as thermal regulation, absorbents, and electrical devices. However, creating such aerogels from cellulosic materials requires complicated preparation processes. Herein, a simple strategy for scalable production of hemp microfibers using a top-down method is reported, which can further be assembled into aerogels with interconnected porous structures via ice-templating technique. With density as low as 2.1 mg cm⁻³, these aerogels demonstrate isotropic superelasticity, as exhibited by their fast shape restoration from over 80% compressive strain. Due to the high porosity (99.87%) and structural tortuosity, these aerogels show a low thermal conductivity of 0.0215 ± 0.0002 W m⁻¹ K⁻¹, suggesting their potential in thermal insulation application. Certain hydrophobic modification using silane derivative further endows these aerogels with reduced water affinity. Overall, the proposed strategy to prepare bio-based microfibers using scalable technology, as well as the assembled aerogels, provides new insights into the design and fabrication of multifunctional bio-based aerogels for value-added applications.     

An Adaptive and Wearable Thermal Camouflage Device

Thermal cloaking and camouflage have attracted increasing attention with the progress of infrared surveillance technologies. Previous studies have been mainly focused on emissivity manipulation or using sophisticated thermal metamaterials. However, emissivity control is only applicable for objects that are warmer than the environment and lower emissivity is usually accompanied with high reflectance of the surrounding thermal signals if they have nonuniform temperature. Metamaterial‐based thermal camouflage holds great promise but their applications on human subjects are yet to be realized. Direct temperature control represents a more desirable strategy to realize dynamically adjustable camouflage within a wide ambient temperature range, but a wearable, portable, and adjustable thermo‐regulation system that is suitable for human subjects has not been developed. This work demonstrates a wearable and adaptive infrared camouflage device responding to the background temperature change based on the thermoelectric cooling and heating effect. The flexible thermoelectric device can realize the infrared camouflage effect to effectively shield the metabolic heat from skin within a wide range of background temperature: 7 °C below and 15 °C above the ambient temperature, showing promise for a broad range of potential applications, such as security, counter‐surveillance, and adaptive heat shielding and thermal control.     

Scalable Flexible Hybrid Membranes with Photonic Structures for Daytime Radiative Cooling

Passive radiative cooling technology can cool down an object by reflecting solar light and radiating heat simultaneously. However, photonic radiators generally require stringent and nanoscale‐precision fabrication, which greatly restricts mass production and renders them less attractive for large‐area applications. A simple, inexpensive, and scalable electrospinning method is demonstrated for fabricating a high‐performance flexible hybrid membrane radiator (FHMR) that consists of polyvinylidene fluoride/tetraethyl orthosilicate fibers with numerous nanopores inside and SiO₂ microspheres randomly distributed across its surface. Even without silver back‐coating, a 300 µm thick FHMR has an average infrared emissivity >0.96 and reflects ≈97% of solar irradiance. Moreover, it exhibits great flexibility and superior strength. The daytime cooling performance this device is experimentally demonstrated with an average radiative cooling power of 61 W m^?2 and a temperature decrease up to 6 °C under a peak solar intensity of 1000 W m^?2. This performance is comparable to those of state‐of‐the‐art devices.     

Carbon Nanotube/Hygroscopic Salt Nanocomposites with Dual-Functionality of Effective Cooling and Fire Resistance for Safe and Ultrahigh-Rate Operation of Practical Lithium-Ion Batteries

Fire and explosion accidents and reduced energy utilization due to poor cycling stability of lithium-ion batteries (LIBs) caused by inevitable internal temperature rise during high-rate operations have become a growing concern. Herein, a dual-functional carbon nanotube/hygroscopic salt (DFCNT/HS) film with effective passive cooling performance and fire insulation for the safe usage of practical LIBs under extremely fast discharging conditions is reported. The DFCNT/HS film based on the cooling mechanism of self-adaptive moisture absorption/desorption delivers a high cooling power of 32.9 W m⁻² K⁻¹, which can reduce the maximum temperature of a 18650–3.6 V/2.0 Ah LIB by 11.2 and 17.4 °C at discharging rates of 10 and 15 C, respectively. Covering the cooling film, the battery discharges 23.6 Ah more total capacity at 10 within 500 cycles. What is challenging, almost three-fold extended lifetime of 425 cycles is achieved at 15 C with an extra total capacity of 467.2 Ah. Meanwhile, the developed film also shows an excellent high-temperature resistance up to 540 °C, which can alleviate the devastating fire propagation. The fast heat dissipation and excellent fire insulation as well as the mechanical flexibility and manufacturing scalability make this new material promising for safe usage of high-rate LIBs with zero energy consumption.     

Highly Elastic and Conductive N‐Doped Monolithic Graphene Aerogels for Multifunctional Applications

The simple synthesis of ultralow‐density (≈2.32 mg cm^?3) 3D reduced graphene oxide (rGO) aerogels that exhibit high electrical conductivity and excellent compressibility are described herein. Aerogels are synthesized using a combined hydrothermal and thermal annealing method in which hexamethylenetetramine is employed as a reducer, nitrogen source, and graphene dispersion stabilizer. The N‐binding configurations of rGO aerogels increase dramatically, as evidenced by the change in pyridinic‐N/quaternary‐N ratio. The conductivity of this graphene aerogel is ≈11.74 S m^?1 at zero strain, whereas the conductivity at a compressive strain of ≈80% is ≈704.23 S m^?1, which is the largest electrical conductivity reported so far in any 3D sponge‐like low‐density carbon material. In addition, the aerogel has excellent hydrophobicity (with a water contact angle of 137.4°) as well as selective absorption for organic solvents and oils. The compressive modulus (94.5 kPa; ρ ≈ 2.32 mg cm^?3) of the rGO aerogel is higher than that of other carbon‐based aerogels. The physical and chemical properties (such as high conductivity, elasticity, high surface area, open pore structure, and chemical stability) of the aerogel suggest that it is a viable candidate for the use in energy storage, electrodes for fuel cells, photocatalysis, environmental protection, energy absorption, and sensing applications.     

Cellulose Silica Hybrid Nanofiber Aerogels: From Sol–Gel Electrospun Nanofibers to Multifunctional Aerogels

Aerogels are considered ideal candidates for various applications, because of their low bulk density, highly porous nature, and functional performance. However, the time intensive nature of the complex fabrication process limits their potential application in various fields. Recently, incorporation of a fibrous network has resulted in production of aerogels with improved properties and functionalities. A facile approach is presented to fabricate hybrid sol–gel electrospun silica‐cellulose diacetate (CDA)‐based nanofibers to generate thermally and mechanically stable nanofiber aerogels. Thermal treatment results in gluing the silica‐CDA network strongly together thereby enhancing aerogel mechanical stability and hydrophobicity without compromising their highly porous nature (>98%) and low bulk density (≈10 mg cm^?3). X‐ray photoelectron spectroscopy and in situ Fourier‐transform infrared studies demonstrate the development of strong bonds between silica and the CDA network, which result in the fabrication of cross‐linked structure responsible for their mechanical and thermal robustness and enhanced affinity for oils. Superhydrophobic nature and high oleophilicity of the hybrid aerogels enable them to be ideal candidates for oil spill cleaning, while their flame retardancy and low thermal conductivity can be explored in various applications requiring stability at high temperatures.     

Bioinspired Intelligent Solar-Responsive Thermally Conductive Pyramidal Phase Change Composites with Radially Oriented Layered Structures toward Efficient Solar–Thermal–Electric Energy Conversion

To remedy the drawbacks of weak solar-thermal conversion capability, low thermal conductivity, and poor structural stability of phase change materials, pyramidal graphitized chitosan/graphene aerogels (G-CGAs) with numerous radially oriented layers are constructed, in which the long-range radial alignment of graphene sheets is achieved by a novel directional-freezing strategy. A G-CGA/polyethylene glycol phase change composite exhibits a thermal conductivity of 2.90 W m⁻¹ K⁻¹ with a latent heat of 178.8 J g⁻¹, and achieves a superior solar-thermal energy conversion and storage efficiency of 90.4% and an attractive maximum temperature of 99.7 °C under a light intensity of 200 mW cm⁻². Inspired by waterlilies, solar-responsive phase change composites (SPCCs) are designed for the first time by assembling the G-CGA/polyethylene glycol phase change composites with solar-driven bilayer films, which bloom by day and close by night. The heat preservation effect of the solar-driven films leads to a higher temperature of SPCC for a longer period at night. The SPCC-based solar–thermal–electric generator achieves output voltages of 499.2 and 1034.9 mV under light intensities of 200 and 500 mW cm⁻², respectively. Even after stopping the solar irradiation, the voltage output still occurs because of the latent heat release and the heat preservation of the films.