Photothermal Materials Research Articles

Hotspots and trends in solar-driven interfacial evaporation technology based on bibliometric management and analysis

The solar-driven interface evaporation technology (SDIE) is an innovative and environmentally friendly desalination method, highly favored by researchers due to its low energy consumption, high efficiency, absence of secondary pollution, and alignment with sustainable development principles. By utilizing widely distributed solar energy as the driving force and employing simple and portable photothermal evaporation structures as the core component, SDIE achieves efficient energy conversion and demonstrates excellent seawater desalination capabilities. Consequently, it has gained significant attention from researchers in both seawater desalination systems and water treatment applications. This paper presents a knowledge framework on seawater SDIE through scientometric analysis of academic documents from 2014 to 2023. The technology is visually analyzed using collaborative networks, reference co-citation networks, and keyword co-discovery techniques. The results demonstrate an exponential increase in the number of documents published over time, highlighting the growing significance of SDIE techniques in interdisciplinary research. Furthermore, this manuscript clarifies the main focus areas in current research including desalination performance evaluation, development of high efficient photothermal materials, system design optimization as well as mechanism analysis. Additionally, existing challenges and future research directions are proposed to provide guidance for SDIE further research.

Carbon nanotube–cesium tungsten oxide–poly(N-isopropylacrylamide) hydrogel-based optical writing display

Studies have attempted to improve thermal conductivity by complexing polymers. Via the complexing of photothermal materials with a heat-sensitive polymer, heat can be generated internally, thus resulting in efficient changes in the properties of the heat-sensitive polymer. This study fabricated an optical writing display to locally induce heat generation in poly(N-isopropylacrylamide) (pNIPAM), which is a heat-responsive material, using the photothermal effect of a near-infrared (NIR) absorbing material. Cesium tungsten oxide (CTO), an NIR-absorbing material, exhibits excellent properties due to its photothermal properties. By mixing carbon nanotubes (CNTs), the photothermal effect caused by NIR rays was strengthened and was more effectively controlled by providing thermal conductivity characteristics. The CNT–CTO hybrid absorbed the NIR laser, converted it into heat, and transmitted it to the adjacent pNIPAM network. When pNIPAM received heat, a hydrophilic–hydrophobic phase transition occurred, and a white pattern was observed owing to a change in the refractive index inside the hydrogel. Upon stopping the application of the NIR laser, rapid cooling occurred due to the high thermal conductivity of the CNTs, and the hydrophobic–hydrophilic phase transition was quickly achieved and restored. Therefore, based on the results of this study, optical writing displays using heat-responsive polymers containing photothermal particles and NIR lasers are expected to be applicable for information transmission in extreme environments, such as aviation, space, and the military, owing to the ability of lasers to travel in a straight line.

An efficient photothermal conversion material based on D‐A type luminophore for solar‐driven desalination

AbstractSolar‐driven interfacial evaporation is a promising technology for desalination. The photothermal conversion materials are at the core and play a key role in this field. Design of photothermal conversion materials based on organic dyes for desalination is still a challenge due to lack of efficient guiding strategy. Herein, a new D (donor)‐A (acceptor) type conjugated tetraphenylpyrazine (TPP) luminophore (namely TPP‐2IND) was prepared as a photothermal conversion molecule. It exhibited a broad absorption spectrum and strong π–π stacking in the solid state, resulting in efficient sunlight harvesting and boosting nonradiative decay. TPP‐2IND powder exhibited high photothermal efficiency upon 660 nm laser irradiation (0.9 W cm−2), and the surface temperature can reach to 200°C. Then, an interfacial heating system based on TPP‐2IND is established successfully. The water evaporation rate and the solar‐driven water evaporation efficiency were evaluated up to 1.04 kg m−2 h−1 and 65.8% under 1 sunlight, respectively. Thus, this novel solar‐driven heating system shows high potential for desalination and stimulates the development of advanced photothermal conversion materials.

A multi-layer fabric for high-efficiency solar-driven seawater desalination

Fiber-based photothermal materials for seawater desalination usage have garnered significant attention owing to their outstanding properties. However, traditional monolayer fabrics are prone to possess inherent inefficiencies such as high thermal dissipation and salt crystallization within the evaporation zone, especially reducing the evaporation efficiency during the long-term seawater desalination. Herein, a novel three-layered three-dimensional (3D) spacer carbon/polyester cotton spacer woven fabric (SWF) evaporator is designed. This SWF material was delineated into three distinct layers: an upper evaporate layer, a foundational water absorption layer, and a central water dedicated to water transition, thermal insulation, and salt crystallization. The rational three-layered 3D architecture guarantees the swift aqueous transition within SWF evaporator, simultaneously curtailing thermal losses from the top layer. The evaporation rate of 3D SWF, with 6 mm interval space, registered at 1.6721 kg · m−2·h−1 under a solar intensity of 1 kW · m−2. Furthermore, under conditions with a solar power of 1 kW · m−2 and a wind velocity of 2 m · s−1, the evaporation efficiency of liquid water from SWF, with a central layer height of 12 mm, culminated at 3.9742 kg · m−2·h−1, which validated its adeptness for the seawater desalination applications. The results of our research are helping to provide for efficient and stable methods of wastewater treatment, desalination, and drinking water collection.

Self-assembled Cu doped NiO loaded reduced graphene oxide: Multifunctional photothermal framework for interfacial water evaporation, disinfection and power generation

Development of self-assembled multifunctional photothermal materials is considered as reconciliation between solar energy harvesting and sustainable energy and environmental applications. Herein, we report strategically designed self-assembled Cu-doped-NiO nanoparticles loaded-rGO (rGO-Cu-NiO) framework. The self-assembly exhibited synergistic photothermal conversion, floatable porous structure for efficient capillary action enabling water transmission and quick steam escape pathways. The optimized rGO-Cu-NiO framework achieved interfacial water evaporation rate of 1.47 kgm−2h−1 with 92% conversion efficiency under 1Sun illumination. Maximum surface temperature of the framework displays 74 °C under 2Sun irradiation, making it highly feasible to be implemented as solar water purifier. Cell viability examination indicated the superior antimicrobial properties, making it a promising candidate for photothermal therapy application. Moreover, the self-assembled rGO-Cu-NiO framework integrated with the commercial thermoelectric module shows outstanding photothermal conversion efficiency to envisage its ability towards electrical power generation. Impressively, the amalgamation of the framework with the Bi2Te3 based commercial thermoelectric module proficiently reinforce the performance of the thermoelectric generator by offering an enhanced power output of 3.91 mW and appreciably high power density of 0.311 mW/cm2. Overall, the excellent stability, no photo-leaching, effectiveness to produce pure water from seawater, antimicrobial properties, recyclability, make rGO-Cu-NiO a perfect epitome of sustainable water treatment and power generation application.

Unique photothermal material: Copper phosphate (Cu3P2O8) with broadband visible-to-near-infrared absorption properties for efficient solar steam generation

Effective harnessing of renewable solar energy in interfacial solar steam generation (ISSG) is a promising solution for addressing freshwater scarcity worldwide. Therefore, the development of photothermal materials plays a pivotal role in achieving efficient ISSG performance. This paper reports on an innovative photothermal material, copper phosphate (Cu3P2O8; CuPO), with broadband visible-to-near-infrared (Vis-to-NIR) absorption for ISSG. CuPO exhibited favorable characteristics, including extensive light absorption across the Vis to NIR spectrum (500–2200 nm), low thermal conductivity (0.64 W/m·K), high photon-to-heat conversion efficiency (87.9 %), and inherent hydrophilicity. When subjected to simulated sunlight (AM1.5G, 100 mW/cm2), the CuPO-coated polyurethane membrane demonstrated remarkable water evaporation performance (2.05 kg/m2·h) and ISSG efficiency (95.0 %). Notably, employing an ultraviolet cutoff filter (< 450 nm) revealed a substantial NIR absorption contribution of CuPO, surpassing 80 % of its overall performance. Moreover, the CuPO photothermal membrane exhibited durable ISSG performance over 25 cycles, underscoring the structural robustness and resilience of CuPO. Our findings offer a promising foundation for designing cost-effective, high-performance ISSG systems utilizing copper-based complex oxides.

Cascade type solar distiller with the use of photothermic materials applied in the treatment of surface water

The biggest challenge in solar energy distillation is the increase the production of treated water, so several research have been done to increase the daily yield of solar distillers, increasing the evaporation of saline water and consequently the condensation of steam. The objective of this work was to analyze the simultaneous performance of three cascade solar distillers with a wave-shaped heat absorber plate and the use of photothermal materials. The experiments were divided into three stages A, B and C. In step A, heat absorption tests of the photothermal materials (gravel, marbles, granite and ceramic tile) were performed. In stage B, the initial productivity of the three distillers (D1, D2 and D3) was measured, and in step C the productivity of the distillers was made with the introduction of photothermal materials in the less productive distillers. It was found that the introduction of photothermal materials (gravel and marbles) in distillers (D2 and D3) resulted in an increase in water production of 8 and 18% respectively.

Preparation of Epoxy Resin/Carbon Black Superhydrophobic Photothermal Materials with Shape Memory Capacity for Anti/De‐Icing

The accumulation of ice can cause damage to various equipment, resulting in numerous economic losses. One promising solution for anti/de‐icing is the use of superhydrophobic materials powered by solar energy. In this study, a multilayer superhydrophobic photothermal materials with anti/de‐icing ability is prepared. First, an epoxy resin (EP) substrate with microstructure is prepared by the template method. Then carbon black (CB) nanoparticles are sprayed on the substrate as the photothermal layer. Finally, fluorine‐modified resin is dip‐coated as the hydrophobic modified layer. The light absorption of this material is 1.6 in the wavelength range of 400–2000 nm. The surface temperature rose to 114.2 °C within 270 s under 1 sun illumination. Additionally, the materials can respond to light stimulation and exhibit shape memory, with a shape recovery rate close to 100%. The air cushions in the micro‐nanostructures delayed the droplet freezing time by nearly two times. The good photothermal properties endowed the materials with photothermal de‐icing performance, which improved the de‐icing efficiency by almost 2.2 times. Furthermore, the materials demonstrate outstanding durability that can resist to mechanical wear, acid‐base corrosion, and UV aging, thermal stability, and self‐cleaning properties, making it highly suitable for outdoor equipment applications.

An effective material for solar steam generation applications: Gradient graphene sponge

The efficient use of solar energy for clean water is a renewable and environmentally-friendly route to solve global water scarcity. For this, we report the preparation of light, mechanically durable, and effective photothermal material. A simple acid impregnation method was applied to graphene sponge material (GSM) possessing hydrophobic character to gain partial hydrophilicity to obtain a gradient structure. The morphological and structural properties of the gradient graphene sponge material (GGSM) were carried out using scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray powder diffraction patterns, Fourier-transformed infrared spectroscopy, and water drop contact angle measurements. GGSM showed fast and effective water vapor conversion performance due to the gradient structure, as well as the high rate of sunlight absorption and photothermal conversion thanks to graphene. With the advantageous feature of gradient structure, GGSM achieved a high water vapor conversion capacity (1.79 kg/m2h) and solar thermal efficiency of 57% compared to GSM (1.58 kg/m2h; 45%). This new material provides a novel approach to solar energy applications.

Solid waste-derived solar desalination devices: Enhanced efficiency in water vapor generation and diffusion

Water scarcity and waste pollution are serious global challenges due to the rapid development of the global economy and population growth. A win–win strategy to address the water crisis and reduce pollution is to use waste materials as low-carbon and eco-friendly photothermal materials for solar-driven desalination. Steel slag, an abundant industrial waste product, has excellent thermal conductivity. Enhancing its light absorption and hydrophilicity could enable the creation of efficient and economical solar seawater desalination devices. In this study, our research introduces a 3D desalination device using this modified slag, achieving a consistent evaporation rate fluctuating around 29 kg m-2h−1 at 4 m s−1 wind speed for five days. This breakthrough can be attributed to the excellent light-to-heat conversion of the modified steel slag, coupled with the synergistic interaction between the porous evaporator and wind, culminating in efficient steam evaporation and diffusion. Life Cycle Analysis (LCA) reveals that the carbon emissions of the modified steel slag for desalinating each ton of seawater are only 2.20 kg CO2-eq, indicating superior prospects for carbon reduction compared to the reverse osmosis (RO) and Multi-Stage Flash Desalination (MSF) processes.

Preparation and characterization of chitosan/ZnO-Ag composite microcapsules and their applications in solar energy harvesting and electromagnetic interference shielding

Phase change microcapsules are known for their latent heat storage capability. However, the efficient absorption and utilization of solar energy by these microcapsules remains a significant challenge. In this study, we successfully prepared composite phase change microcapsules containing ZnO-Ag nanospheres, chitosan, and paraffin. These microcapsules demonstrated remarkable photothermal conversion efficiency. ZnO was found to effectively absorb ultraviolet light, while the plasmonic resonance of Ag was utilized to absorb and make use of light energy in the visible region. Moreover, due to the synergistic absorption and reflection of electromagnetic waves by ZnO-Ag nanoparticles and graphene, the well-dispersed chitosan/ZnO-Ag composite microcapsules and graphene in the fabric coating demonstrated exceptional electromagnetic shielding performance. In addition, the coated fabric based on composite microcapsules exhibited excellent antibacterial properties, effectively inhibiting the growth of bacteria such as S. aureus and E. coli. This antibacterial performance adds to their potential applications in various fields. These multifunctional phase change microcapsules offer vast potential for the effective utilization of solar energy, serving as efficient photothermal conversion and energy storage materials.

Waste Tea-Derived Theabrownins for Solar-Driven Steam Generation.

Solar-driven seawater desalination has been considered an effective and sustainable solution to mitigate the global freshwater crisis. However, the substantial cost associated with photothermal materials for evaporator fabrication still hinders large-scale manufacturing for practical applications. Herein, we successfully obtained high yields of theabrownins (TB), which were oxidation polymerization products of polyphenols from waste and inferior tea leaves using a liquid-state fermentation strategy. Subsequently, a series of photothermal complexes were prepared based on the metal-phenolic networks assembled from TB and metal ions (Fe(III), Cu(II), Ni(II), and Zn(II)). Also, the screened TB@Fe(III) complexes were directly coated on a hydrophilic poly(vinylidene fluoride) (PVDF) membrane to construct the solar evaporation device (TB@Fe(III)@PVDF), which not only demonstrated superior light absorption property and notable hydrophilicity but also achieved a high water evaporation rate of 1.59 kg m-2 h-1 and a steam generation efficiency of 90% under 1 sun irradiation. More importantly, its long-term stability and exceptionally low production cost enabled an important step toward the possibility of large-scale practical applications. We believe that this study holds the potential to pave the way for the development of sustainable and cost-effective photothermal materials, offering new avenues for utilization of agriculture resource waste and solar-driven water remediation.

Heat transfer behavior of graphene-based photothermal conversion materials prepared with tube array-porous network composite structure

In order to solve the problems of low energy utilization and poor structural stability of photothermal conversion materials, a graphene-based photothermal conversion material was prepared, which was structurally integrated with a light-absorbing upper layer and a heat insulating base. During the preparation process, a tightly arranged nanotube array upper layer was constructed on the basis of graphene films by microimprinting technology, and a porous aerogel base was molded by a fixed-point titration and multiple-foaming method. The results show that the light trap constructed from graphene hollow nanotubes can significantly increase the number of light reflections and reduce light reflectivity. Meanwhile, the length of the nanotubes is directly proportional to the light-absorbing capacity of the material, which can increase the light-absorbing rate to more than 98% under the embossing conditions of 85 kN and 8h. In addition, the porous aerogel insulation base can effectively improve the photothermal conversion effect, and a photothermal conversion efficiency of 87% and a water evaporation rate of 1.3 kg/(m2 h) can be achieved at a base thickness of 6 mm.

Gyroid‐Structured Au Materials with 3D Interconnected Networks for Highly Efficient Heat Localization and Solar Vapor Generation

Effective solar steam generation is regarded as a prospective technology for seawater desalination and water purification, owing to its capability of solar light absorption and heat conversion. Numerous efforts have been dedicated to exploring photothermal materials with various delicate microstructures. However, investigations of the coupling effect of structure and component still need to be done. Herein, a superior solar steam generator of 3D bicontinuous interconnected gyroid‐structured Au materials (Au gyroid) by depositing Au nanoparticles onto C. rubi butterfly wings is reported. Au gyroid is proven to possess the evaporation rate and efficiency of 1.29 kg m−2 h−1 and 74.0%, under 1 sun irradiation. What is more, the evaporation rate and efficiency of lattice‐structured Au materials (Au lattice) as a comparison are 1.14 kg m−2 h−1 and 65.4%. The outstanding performance of Au gyroid is mainly ascribed to its 3D densely distributed hotspots and interconnected nanochannels, which are beneficial for strong broadband light absorption, sufficient water supply, as well as confinement effect for water heating. This work will provide insight into the future design and synthesis of novel plasmonic absorbers in photothermal conversion, photocatalysis, and photovoltaic devices.

Light-induced MOF synthesis enabling composite photothermal materials

Metal-organic frameworks (MOFs) are a class of porous materials known for their large surface areas. Thus, over the past few decades the development of MOFs and their applications has been a major topic of interest throughout the scientific community. However, many current conventional syntheses of MOFs are lengthy solvothermal processes carried out at elevated temperatures. Herein, we developed a rapid light-induced synthesis of MOFs by harnessing the plasmonic photothermal abilities of bipyramidal gold nanoparticles (AuBPs). The generality of the photo-induced method was demonstrated by synthesizing four different MOFs utilizing three different wavelengths (520 nm, 660 nm and 850 nm). Furthermore, by regulating light exposure, AuBPs could be embedded in the MOF or maintained in the supernatant. Notably, the AuBPs-embedded MOF (AuBP@UIO-66) retained its plasmonic properties along with the extraordinary surface area typical to MOFs. The photothermal AuBP@UIO-66 demonstrated a significant light-induced heating response that was utilized for ultrafast desorption and MOF activation.

A Tent-Inspired Portable Solar-Driven Water Purification Device for Wilderness Explorers.

Wilderness adventure favored by many enthusiasts often endanger lives due to lacking freshwater or drinking contaminated water. Therefore, compared to the inefficient methods of filtration, steaming, and direct solar heating, it is of great meaningfulness to develop a solar-driven water purification device with efficiency, lightweight, portability, and multi-water-quality purification by taking full advantage of solar-driven interfacial evaporation. Here, a tent-inspired portable solar-driven water purification device consisting of Janus-structured bacterial cellulose aerogel (JBCA) solar evaporator and tent-type condensation recovery device is reported. For the JBCA solar evaporator, it is prepared from biomass bacterial cellulose (BC) as raw material and hydroxylated carbon nanotubes (HCNT) as photothermal material, and the Janus property is achieved by the assistance of hydrophobic and hydrophilic chemical cross-linking. It exhibits lightweight, unibody, high photothermal conversion, efficient evaporation, and multi-water-quality purification capability for representative seawater, urine, and bacterial river water. For the tent-type condensation recovery device, it is based on the prototype of tent and uses flexible ultra-transparent polyvinyl chloride (PVC) film as raw material. Thanks to the rational prototype and material selection, it displays outstanding portability and lightweight through the folding/unfolding method. Therefore, the designed tent-inspired portable solar-driven water purification device demonstrates great potential application in wilderness exploration.

Photothermal Conversion Perylene-Based Metal-Organic Framework with Panchromatic Absorption Bandwidth across the Visible to Near-Infrared.

Recently, facilely designable metal-organic frameworks have gained attention in the construction of photothermal conversion materials. Nonetheless, most of the previously reported photothermal conversion metal-organic frameworks exhibit limited light absorption capabilities. In this work, a distinctive metal-organic framework with heterogeneous periodic alternate spatial arrangements of metal-oxygen clusters and perylene-based derivative molecules was prepared by in situ synthesis. The building blocks in this inimitable structure behave as both electron donors and electron acceptors, giving rise to the significant inherent charge transfer in this crystalline material, resulting in a narrow band gap with excellent panchromatic absorption, with the ground state being the charge transfer state. Moreover, it can retain excellent air-, photo-, and water-stability in the solid state. The excellent stability and broad light absorption characteristics enable the effective realization of near-infrared (NIR) photothermal conversion, including infrequent NIR-II photothermal conversion, in this perylene-based metal-organic framework.

Eco-Friendly Flame-Retardant Phase-Change Composite Films Based on Polyphosphazene/Phosphorene Hybrid Foam and Paraffin Wax for Light/Heat-Dual-Actuated Shape Memory.

Multiactuated shape memory materials are a class of promising intelligent materials that have received great interest in the fields of self-healing, anticounterfeiting, biomedical, soft robotic, and smart thermal management applications. To obtain a light/heat-dual-actuated shape memory material for thermal management applications in fire safety, we have designed a type of halogen-free flame-retardant phase-change composite film based on polyaryloxyphosphazene (PDAP)/phosphorene (PR) hybrid foam as a support material and paraffin wax (PW) as a phase-change material (PCM). PDAP was synthesized as a flexible foam matrix through the ring-opening polymerization of hexachlorocyclotriphosphazene, followed by a substitution reaction of aryloxy groups. The porosity of the PDAP foam is improved by introducing PR nanosheets, facilitating a high latent heat capacity of the PDAP-PR/PW composite films for thermal management applications. The PDAP-PR/PW composite films can implement rapid shape recovery within 65 s in the heating process, which is much shorter than that of the corresponding film without PR nanosheets (185 s). Furthermore, the PDAP-PR/PW composite films also exhibit light-actuated shape memory behavior thanks to their good solar-to-thermal energy absorption and conversion contributed by PR nanosheets as a highly effective photothermal material. More importantly, the presence of PR nanosheets imparts an excellent flame-retardant property to the PDAP-PR/PW composite films. The PDAP-PR/PW composite film can be self-extinguished within 2 s after the flame. Through an innovative integration of flexible polyphosphazene foam, PR nanosheets, and solid-liquid PCM to obtain a sensitive actuating response to light and heat, this study offers a new approach for developing multiactuated and eco-friendly flame-retardant shape memory materials to meet the requirement of applications with a requirement of fire safety in soft actuators, thermal therapy, control devices, and so on.

Black kitchen waste based solar evaporator employing radiative cooling film as difffuse substrate for efficient desalination

Many substances looks black often means that these substance can completely absorb ultraviolet radiation and Visible incident light (UV). Ultraviolet and visible light account for 57 % of the incident energy of the sun. There are many substances that looks black, but have not been paid attention in the field of photothermal interface evaporation. Based on the above discussion, this paper selects the waste black round plastic lunch box and a piece of black garbage bag as solar photothermal materials to make a solar desalination device, and proves that these black garbage can be recycled and reused to make an interface solar evaporator. In this paper, a 2D desalination device with photothermal interface evaporation for solar thermal conversion was successfully fabricated using only black round plastic lunch box as photothermal material and polyester cloth as water delivery channel. In addition, a black garbage plastic bag as the only solar photothermal conversion material has also been reused in the preparation of 3D evaporators. Using the radiation cooling film as the diffuse reflection substrate, the 3D device makes the incident sunlight reflected from the radiation cooling film and polyester cloth to the black garbage plastic bag many times, making the whole evaporation device. It can reabsorb solar incident light many times. After testing, the solar energy absorption rate of the 3D evaporator is as high as 96.6 %, and the steam output is as high as 8.96 kg m−2 h−1.

Shooting Three Birds with One Stone: Device Construction and Thermal Management for Simultaneous Photothermal Conversion Water Evaporation, Thermoelectric Generation and Photocatalytic Degradation

AbstractIt's a promising way to address the global freshwater crisis and energy shortage through solar‐driven devices with evaporate, degrade, and generate electricity at the same time. Low‐efficient light‐thermal conversions for multi‐usage limit application. This paper presents a low‐cost melamine foam/TiO2/carbon black/bismuth (MF/TiO2/CB/Bi) composite with excellent activity to simultaneously process photothermal water evaporation, pollutant degradation, and thermoelectric output, namely‚ shooting three birds with one stone. Under 1 sunlight light intensity, the water evaporation rate reach 4.235 kg m−2 h−1, and the maximum electric power output of a single module is 0.733 W m−2. Meanwhile, Rhodamine B (RhB) solution with 4.0 × 10−4 mol L−1 can be almost degraded within 60 min. Excellent performance benefits from the enhanced adsorption by chemicals, 3D structure for accepting more incident light, and hydrophilic group reducing evaporation enthalpy. Combined with the simulation and experiment, the relationship between heat distribution and thicknesses is studied. When less than 1.98 cm, the lateral temperature is higher than the ambient temperature, thus additional energy cannot be obtained. This work provides a facile and novel method for the construction of photothermal conversion materials with multi‐functional, as a new and useful attempt to solve the shortage of fresh water and electric energy, as well as environmental pollution.