Advances in photothermal regulation strategies: from efficient solar heating to daytime passive cooling

Bismuth-Tin Core-Shell Particles From Liquid Metals: A Novel, Highly Efficient Photothermal Material that Combines Broadband Light Absorption with Effective Light-to-Heat Conversion

This study presents a pioneering investigation of hybrid bismuth-tin (BiSn) liquid metal particles for photothermal applications. It is shown that the intrinsic core-shell structure of liquid metal particles can be instrumentalized to combine the broadband absorption characteristics of defect-rich nano-oxides and the high light-to-heat conversion efficiency of metallic particles. Even though bismuth or tin does not show any photothermal characteristics alone, optimization of the core-shell structure of BiSn particles leads to the discovery of novel, highly efficient photothermal materials. Particles with optimized structures can absorb 85% of broadband light and achieve over 90% photothermal conversion efficiency. It is demonstrated that these particles can be used as a solar absorber for solar water evaporation systems owing to their broadband absorption capability and become a non-carbon alternative enabling scalable applications. We also showcased their use in polymer actuators in which a near-infrared (NIR) response stems from their oxide shell, and fast heating/cooling rates achieved by the metal core enable rapid response and local movement. These findings underscore the potential of BiSn liquid metal-derived core-shell particles for diverse applications, capitalizing on their outstanding photothermal properties as well as their facile and scalable synthesis conditions.

Controllable preparation of graphene glass fiber fabric towards mass production and its application in self-adaptive thermal management

Direct synthesis of graphene on nonmetallic substrates via chemical vapor deposition (CVD) has become a frontier research realm targeting transfer-free applications of CVD graphene. However, the stable mass production of graphene with a favorable growth rate and quality remains a grand challenge. Herein, graphene glass fiber fabric (GGFF) was successfully developed through the controllable growth of graphene on non-catalytic glass fiber fabric, employing a synergistic binary-precursor CVD strategy to alleviate the dilemma between growth rate and quality. The binary precursors consisted of acetylene and acetone, where acetylene with high decomposition efficiency fed rapid graphene growth while oxygen-containing acetone was adopted for improving the layer uniformity and quality. Notably, the bifurcating introducing-confluent premixing (BI-CP) system was self-built for the controllable introduction of gas and liquid precursors, enabling the stable production of GGFF. GGFF features solar absorption and infrared emission properties, based on which the self-adaptive dual-mode thermal management film was developed. This film can automatically switch between heating and cooling modes by spontaneously perceiving the temperature, achieving excellent thermal management performances with heating and cooling power of ∼501.2 and ∼108.6 W m-2, respectively. These findings unlock a new strategy for the large-scale batch production of graphene materials and inspire advanced possibilities for further applications.

Recent innovations in 3D solar evaporators and their functionalities

Interfacial solar evaporation (ISE) has emerged as a promising technology to alleviate global water scarcity via energy-efficient purification of both wastewater and seawater. While ISE was originally identified and developed during studies of simple double-layered two-dimensional (2D) evaporators, observed limitations in evaporation rate and functionality soon led to the development of three-dimensional (3D) evaporators, which is now recognized as one of the most pivotal milestones in the research field. 3D evaporators significantly enhance the evaporation rates beyond the theoretical limits of 2D evaporators. Furthermore, 3D evaporators could have multifaceted functionalities originating from various functional evaporation surfaces and 3D structures. This review summarizes recent advances in 3D evaporators, focusing on rational design, fabrication and energy nexus of 3D evaporators, and the derivative functions for improving solar evaporation performance and exploring novel applications. Future research prospects are also proposed based on the in-depth understanding of the fundamental aspects of 3D evaporators and the requirements for practical applications.

Plasmonic Pd-Sb nanosheets for photothermal CH4 conversion to HCHO and therapy

Photothermal catalysis effectively increases catalytic activity by using the photothermal effect of metal nanomaterials; however, the combination of strong light absorption and high catalytic performance remains a challenge. Here, we demonstrate hexagonal ~5-nanometer-thick palladium antimony (chemical formula as Pd8Sb3) nanosheets (NSs) that exhibit strong light absorption within full spectral and localized surface plasmon resonance (LSPR) effects in the visible region. Such LSPR features lead to strong photothermal effects, and Pd8Sb3 NSs aqueous dispersion enables enhanced photothermal methane (CH4) conversion to formaldehyde (HCHO) under full-spectrum light irradiation at 1.7 watts per square centimeter, leading to selectivity of ~98.7%, productivity of ~665 millimoles per gram of catalyst, ~700 times higher than that of Pd NSs. Mechanism investigations suggest that different radicals were generated on Pd8Sb3 (·OH) and Pd NSs (·O2-), where Pd8Sb3 NSs displays stronger adsorption strength to CH4 and facilitates CH4 oxidation to HCHO. Besides, the strong light absorption ability of Pd8Sb3 NSs enables photothermal therapy for breast cancer.

Superhydrophobic Solar-to-Thermal Materials Toward Cutting-Edge Applications

Solar-to-thermal conversion is a direct and effective way to absorb sunlight for heat via the rational design and control of photothermal materials. However, when exposed to water-existed conditions, the conventional solar-to-thermal performance may experience severe degradation owing to the high specific heat capacity of water. To tackle with the challenge, the water-repellent function is introduced to construct superhydrophobic solar-to-thermal materials (SSTMs) for achieving stable heating, and even, for creating new application possibilities under water droplets, sweat, seawater, and ice environments. An in-depth review of cutting-edge research of SSTMs is given, focusing on synergetic functions, typical construction methods, and cutting-edge potentials based on water medium. Moreover, the current challenges and future prospects based on SSTMs are also carefully discussed.

Biomimetic Multifunctional Graphene-Based Coating for Thermal Management, Solar De-Icing, and Fire Safety: Inspired from the Antireflection Nanostructure of Compound Eyes

Due to the ubiquitous and inexhaustible solar source, photothermal materials have gained considerable attention for their potential in heating and de-icing. Nevertheless, traditional photothermal materials, exemplified by graphene, frequently encounter challenges emanating from their elevated reflectance. Inspired by ocular structures, this study uses the Fresnel equation to enhance the photo-thermal conversion efficiency of graphene by introducing a polydimethylsiloxane (PDMS)/silicon dioxide (SiO2) coating, which reduces the light reflectance (≈20%) through destructive interference. The designed coating achieves an equilibrium temperature of ≈77 °C at one sun and a quick de-icing in ≈65 s, all with a thickness of 5 µm. Simulations demonstrate that applying this coating to high-rise buildings results in energy savings of ≈31% in winter heating. Furthermore, the combination of PDMS/SiO2 and graphene confers a notable enhancement in thermal stability through a synergistic flame-retardant mechanism, effectively safeguarding polyurethane against high temperatures and conflagrations, leading to marked reduction of 58% and 28% in heat release rate and total heat release. This innovative design enhances the photo-thermal conversion, de-icing function, and flame retardancy of graphene, thereby advancing its applications in outdoor equipment, high-rise buildings, and aerospace vessels.

Dynamical Janus-Like Behavior Excited by Passive Cold-Heat Modulation in the Earth-Sun/Universe System: Opportunities and Challenges

The utilization of solar-thermal energy and universal cold energy has led to many innovative designs that achieve effective temperature regulation in different application scenarios. Numerous studies on passive solar heating and radiation cooling often operate independently (or actively control the conversion) and lack a cohesive framework for deep connections. This work provides a concise overview of the recent breakthroughs in solar heating and radiation cooling by employing a mechanism material in the application model. Furthermore, the utilization of dynamic Janus-like behavior serves as a novel nexus to elucidate the relationship between solar heating and radiation cooling, allowing for the analysis of dynamic conversion strategies across various applications. Additionally, special discussions are provided to address specific requirements in diverse applications, such as optimizing light transmission for clothing or window glass. Finally, the challenges and opportunities associated with the development of solar heating and radiation cooling applications are underscored, which hold immense potential for substantial carbon emission reduction and environmental preservation. This work aims to ignite interest and lay a solid foundation for researchers to conduct in-depth studies on effective and self-adaptive regulation of cooling and heating.

Cost Effective Photothermal Materials Selection for Direct Solar-Driven Evaporation

The cornerstone of eco-friendly and affordable freshwater generation lies in harnessing solar energy for water evaporation. This process involves extracting vapor from liquid water using solar energy. Numerous innovative, low-cost materials have been proposed for this purpose. These materials aim to enable highly controllable and efficient conversion of solar energy into thermal energy while maintaining high cost-effectiveness. Here, in this review paper, we outline the advancements in solar-driven evaporation technology with a focus on optimizing synthesis methods and materials cost. It prioritizes refining evaporation efficiency and affordability using inventive manufacturing methods. By utilizing innovative reasonably priced materials, this process not only ensures efficient resource utilization but also fosters technological advancements in renewable energy applications. Moreover, the affordability of these materials makes solar-powered water evaporation accessible to a wider range of communities, empowering them to address water scarcity challenges.

High-Efficiency Thermal-Shock Resistance Enabled by Radiative Cooling and Latent Heat Storage

Radiative cooling technology is well known for its subambient temperature cooling performance under sunlight radiation. However, the intrinsic maximum cooling power of radiative cooling limits the performance when the objects meet the thermal shock. Here, a dual-function strategy composed of radiative cooling and latent heat storage simultaneously enabling the efficient subambient cooling and high-efficiency thermal-shock resistance performance is proposed. The electrospinning and absorption-pressing methods are used to assemble the dual-function cooler. The high sunlight reflectivity and high mid-infrared emissivity of radiative film allow excellent subambient temperature of 5.1 °C. When subjected the thermal shock, the dual-function cooler demonstrates a pinning effect of huge temperature drop of 39 °C and stable low-temperature level by isothermal heat absorption compared with the traditional radiative cooler. The molten phase change materials provide the heat-time transfer effect by converting thermal-shock heat to the delayed preservation. This strategy paves a powerful way to protect the objects from thermal accumulation and high-temperature damage, expanding the applications of radiative cooling and latent heat storage technologies.

High-Entropy Photothermal Materials

High-entropy (HE) materials, celebrated for their extraordinary chemical and physical properties, have garnered increasing attention for their broad applications across diverse disciplines. The expansive compositional range of these materials allows for nuanced tuning of their properties and innovative structural designs. Recent advances have been centered on their versatile photothermal conversion capabilities, effective across the full solar spectrum (300-2500 nm). The HE effect, coupled with hysteresis diffusion, imparts these materials with desirable thermal and chemical stability. These attributes position HE materials as a revolutionary alternative to traditional photothermal materials, signifying a transformative shift in photothermal technology. This review delivers a comprehensive summary of the current state of knowledge regarding HE photothermal materials, emphasizing the intricate relationship between their compositions, structures, light-absorbing mechanisms, and optical properties. Furthermore, the review outlines the notable advances in HE photothermal materials, emphasizing their contributions to areas, such as solar water evaporation, personal thermal management, solar thermoelectric generation, catalysis, and biomedical applications. The review culminates in presenting a roadmap that outlines prospective directions for future research in this burgeoning field, and also outlines fruitful ways to develop advanced HE photothermal materials and to expand their promising applications.

The Influence of Light-Generated Radicals for Highly Efficient Solar-Thermal Conversion in an Ultra-Stable 2D Metal-Organic Assembly

Solar-thermal water evaporation is a promising strategy for clean water production, which needs the development of solar-thermal conversion materials with both high efficiency and high stability. Herein, we reported an ultra-stable cobalt(II)-organic assembly NKU-123 with light-generated radicals, exhibiting superior photothermal conversion efficiency and high stability. Under the irradiation of 808 nm light, the temperature of NKU-123 rapidly increases from 25.5 to 215.1 °C in 6 seconds. The solar water evaporator based on NKU-123 achieves a high solar-thermal water evaporation rate of 1.442 and 1.299 kg m-2 h-1 under 1-sun irradiation with a water evaporation efficiency of 97.8 and 87.9 % for pure water and seawater, respectively. A detailed mechanism study revealed that the formation of light-generated radicals leads to an increase of spin density of NKU-123 for enhancing the photothermal effect, which provides insights into the design of highly efficient photothermal materials.

Modulating band structure through introducing Cu0/CuxO composites for the improved visible light driven ammonia synthesis

The photocatalytic performance of ceria-based materials can be tuned by adjusting the surface structures with decorating the transition-metal, which are considered as the important active sites. Herein, cuprous oxide-metallic copper composite-doped ceria nanorods were assembled through a simple hydrothermal reduction method. The photocatalytic ammonia synthesis rates exhibit an inverted "V-shaped" trend with increasing Cu0/CuxO mole ratio. The best ammonia production rate, approximately 900 or 521 µmol·gcal-1·h-1 under full-spectra or visible light, can be achieved when the Cu0/CuxO ratio is approximately 0.16, and this value is 8 times greater than that of the original sample. The absorption edge of the as-prepared samples shifted towards visible wavelengths, and they also had appropriate ammonia synthesis levels. This research provides a strategy for designing noble metal-free photocatalysts through introducing the metal/metallic oxide compositesto the catalysts.

Sustainable thermal energy harvest for generating electricity

Electricity is the lifeblood of modern society. However, the predominant source of electricity generation still relies on non-renewable fossil fuels, whose combustion releases greenhouse gases contributing to global warming. The increasing demand for energy and escalating environmental concerns necessitate proactive measures to develop innovative green energy technologies capable of both cooling the Earth and generating electricity. Here, we look forward to an interdisciplinary power system integrating solar absorbers, radiative coolers, and thermoelectric generators. This system can simultaneously harvest thermal energy from the sun and from cold space, thereby transforming the challenges posed by global warming into opportunities for the production of clean electricity. We underscore recent advancements in this field and address key challenges while also exploring forward-looking opportunities in the foreseeable future. The proposed integrated energy technology achieves uninterrupted power supply through the unrestricted capture of thermal energy, offering a robust alternative pathway for next-generation sustainable energy technologies.

Self-sustained and Insulated Radiative/Evaporative Cooler for Daytime Subambient Passive Cooling

Passive cooling technologies are one of the promising solutions to the global energy crisis due to no consumption of fossil fuels during operation. However, the existing radiative and evaporative coolers still have problems achieving daytime subambient cooling while maintaining evaporation over the long term. Here, we propose a self-sustained and insulated radiative/evaporative cooler (SIREC), which consists of a porous polyethylene film (P-PE) at the top, an air layer in the middle, and poly(vinyl alcohol) hydrogel with lithium bromide (PLH) at the bottom. In particular, the P-PE shows high solar reflectance (R̅solar = 0.91) and long-wave infrared transmittance (τ̅LWIR = 0.92), which reflects sunlight while enhancing the direct radiative heat transfer between outer space and PLH (ε̅LWIR = 0.96) for sky radiative cooling. In addition, the desirable vapor permeability (579 s m-1) of the P-PE also results in good compatibility with PLH for evaporative cooling (EC). Moreover, the PLH's ability to harvest atmospheric water at night provides self-sustainment for daytime EC. The air layer between P-PE and PLH further enhances the subambient cooling performance of the SIREC. These findings indicate promising prospects for the integration of passive cooling technologies.