Flexible and Washable CNT-Embedded PAN Nonwoven Fabrics for Solar-Enabled Evaporation and Desalination of Seawater

An Extremely Salt-Resistant Hydrogel-Based Solar Evaporator for Stable Saturated Brine Desalination

Hydrogel-based solar evaporators are widely concerned because of their excellent evaporation performance due to the "water activation" effect by reducing the evaporation enthalpy. However, the current challenge is the trade-off between a high evaporation rate and salt tolerance. Here, a 3D chitosan-based hydrogel evaporator with a directional vertical channel structure using a one-pot in situ strategy and directional freezing method, is innovatively designed. Owing to its vertical channel structure, salt ions can quickly return, while steam can overflow without obstruction, allowing the evaporator to achieve a high evaporation rate and exceptional salt resistance, simultaneously. Consequently, an extremely salt-resistant system is achieved, even in saturated brine (salinity of 26.47 wt.%), with no salt crystals accumulating after continuous over 8 h of evaporation and an excellent evaporation rate of 2.83 kg m-2 h-1 under one sun illumination. This is the best reported salt-resistant hydrogel-based evaporation system. With the record-high salt resistance, this work improves the practicality of hydrogel evaporators for high-salinity desalination.

Efficient Double-Layer Evaporators with Adjustable Pores for Sustainable Solar Evaporation

Solar-driven desalination technology is currently an important way to obtain freshwater resources. Significantly, porous materials are used as substrate materials of interface solar evaporator, and their specific impact of water transport property and thermal management during evaporation is worth exploring. In this paper, poly(vinyl alcohol) (PVA) sponges were prepared by a chemical foaming method, adjusted the PVA polymerization degree, and formaldehyde-hydroxyl ratio to regulate the pore size, and polypyrrole (PPy) was grown in situ on the surface skeleton of PVA sponge to construct a new interfacial solar evaporator (PPy/PVA) with different pore structures. As the size of the evaporator pore changes, the trends in the water transport property and thermal management capability are opposite. Among them, the PPy/PVA-3 evaporator achieves a surface temperature of 38.9 °C and an evaporation rate of 1.764 kg m-2 h-1 under 1 Sun light. And the evaporation efficiency exceeds the theoretical limit (100%). This is because it has the optimal pore structure to balance the competition mechanism between the two aspects. At the same time, the evaporator exhibits good cyclability, stability, and self-cleaning capability. In addition, the evaporator has practical applicability with good purification of both organic dyes and seawater.

Blacking any Material Surface by Amyloid-Fortified Carbon Coating Toward High-Performance Large-Scale Solar Steam Generation System

Enhancing the interfacial adhesion between carbon-based coatings and substrates through a simple method remains a challenge, mainly due to the intrinsic chemical inertness of carbon materials. Herein, a carbon nanosphere-based coating utilizing an amyloid-like protein aggregation strategy is developed, involving only the reaction of protein, reductant, and carbon nanospheres in an aqueous solution at room temperature. The resultant coating, enriched in amyloid-like protein structures, features both robust interfacial adhesion and high light absorption (≈98.5%) covering the entire UV/Vis to NIR regions. Adhesion energy between the coating and the glass exceeds 5436 J m-2, which is at least five times higher than those polymer-reinforced carbon-based coatings. Combining the strong adhesion and excellent photothermal conversion performance of this coating, a solar steam generation system is constructed with a water treatment capacity of 13.01 kg m-2 d-1, which is sufficient to provide daily supply for tens of people. Importantly, the photothermal conversion unit can be repeatedly cleaned and rolled up for storage, which is beneficial for the construction of portable devices. This work provides a facile and valuable method for preparing carbon-based coatings with strong interfacial adhesion, exhibiting great promise in energy conversion and storage, flexible wearable sensors, photothermal therapy, and so on.

Salt Resistant PPy/MXene Flexible Waffle Type Fabric for Efficient Solar Evaporation and Water Purification Production

In recent years, with the development of solar seawater desalination technology, many solar evaporators are affected by precipitated salts during the evaporation process, which can reduce efficiency. In this work, flexible fabrics made of polypyrrole (PPy)/MXene are obtained by impregnating the prepared PPy ink onto waffle like fabrics. The combination of PPy and fabric greatly improves the water absorption and evaporation performance of the fabric. The average evaporation rate of this structure is 1.43 kg m-2 h-1, and the average evaporation efficiency under a single light source is 85.13%. After a 15-h testing cycle and a total of 8 cycles, lasting nearly 120 h, the performance of the device remained stable. The structural characteristics of waffle fabric, based on the Marangoni thermal effect, make it possible to suppress salt precipitation during evaporation, avoiding large salt particles covering the evaporation surface and reducing efficiency. This experiment successfully demonstrated long-term stable water evaporation, providing new ideas for the development of fabric evaporators.

De novo Cu-MOF@CNS nanocomposite coated on a cotton fibrils framework for sustainable solar-driven desalination

Environmental researchers are extremely concerned about addressing the declining availability of drinking water, which is a critical issue in many nations. Solar-driven desalination is an emerging and pioneering renewable approach to reduce potable water scarcity that is suitable for remote locations, developing countries, and disaster zones as it does not require additional energy supply. However, there are still issues with the scalable preparation of photothermal materials, such as achieving low cost and widening the assortment of useful applications. Conventional carbon- and metal-based absorbers are intricate and fragile, which make them difficult to install and transport in places with minimal infrastructure. Thus, a universal process for creating adaptable solar evaporators is sorely required. Herein, we have come up with a holistic approach using a solar absorber (GJ-01(Cal)) derived from a Cu-MOF (HKUST-1) and carbon nanosheets (CNSs) for generating potable water from saline water using solar radiation. The as-synthesized material provides high-performance photothermal water evaporation when illuminated under solar irradiation at the air-water interface. Moreover, its porous structure, high photothermal conversion efficiency, rapid water flow, and heat insulation make it appropriate for saline water desalination. CNS play a pivotal role in improving the photothermal features of the solar absorber (GJ-01(Cal)) in terms of conjugation to promote Cu(0) species and pyrrolic nitrogen (P-N) amplification and thereby enrich the p-type nature of the absorber's triphasic configuration. With these photothermal factors, the localised surface plasmon resonance (LSPR) of electrons increases and achieves high solar spectrum absorption. The GJ-01(Cal) was further coated on porous cotton fibrils (CF) that regulate photothermal interfacial evaporation (PTIE) by allowing water transportation via capillary action. This assemblage of the nanocomposite on CF efficiently evaporates water at a higher surface temperature of ∼47 °C under one solar illumination, achieving 4.23 kg m-2 h-1 of evaporation flux and 96.5% light-to-heat conversion efficiency. Interestingly, the GJ-01(Cal) coated over CF can be recycled at least 10 times. Additionally, it offers scalable production for higher photothermal efficiency with a flexible substrate as a solar evaporator and is beneficial for society paving new horizons towards a sustainable environment.

Deep eutectic supramolecular polymer functionalized MXene for enhancing mechanical properties, photothermal conversion, and bacterial inactivation of cellulose textiles

Two-dimensional (2D) transition metal carbides (Ti3C2Tx MXene) have gained significant attention for their potential in constructing diverse functional materials, However, MXene is easily oxidized and weakly bound to the cellulose matrix, which pose challenges in developing MXene-decorated non-woven fabric with strong bonding and stable thermal management properties. Herein, we successfully prepared deep eutectic supramolecular polymer (DESP) functionalized MXene to address these issues. MXene can be wrapped with DESP to be insulated from water and protected from being oxidized. Subsequently, we achieved an efficient in-situ deposition of DESP-functionalized MXene onto fibers through a combination of dip coating and photopolymerization technique. The resulting nonwoven fabric (CNs-DESP@M) exhibited excellent photothermal conversion properties along with rapid thermal response and functional stability. Interestingly, the interface bonding between MXene and the fiber surface was significantly enhanced due to the abundant pyrogallol groups in DESP, resulting in the composite textile exhibiting commendable mechanical properties (2.68 MPa). Moreover, the as-prepared textile demonstrates outstanding bactericidal efficacy against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The multifunctional textile, created through a facile and efficient approach, demonstrates remarkable potential for applications in smart textiles, catering to the diverse needs of individuals in the future.

Solar interfacial evaporation devices for desalination and water treatment: Perspective and future

Water is an essential commodity for society, and alternate resources such as seawater and wastewater are vital for the future. There are various desalination technologies that can provide sufficient and sustainable water sources. Renewable energy-based desalination technologies like solar-based interfacial evaporation are very efficient and sustainable desalination methods. Solar-based interfacial evaporation has been a focus due to its efficient and easy-to-use methods. Still, research is needed for fouling resistance, scalable and low-cost materials, and devices for solar interfacial evaporation. Recent research focuses on the materials for evaporation devices, but various other aspects of device design and fabrication methods are also necessary to improve device performance. In this article, all the evaporator device configurations and strategies for efficient evaporator devices are compiled and summarized. The evaporator devices have been classified into eight main categories: monolayer, bilayer, tree-like design, low-temperature designs, 3D-Origami-based designs, latent heat recovery design, design with storage/batch process, and contactless design. It was found that a good absorber, well-engineered air-water interface, and bottom-layer insulation are necessary for the best systems. The current research focuses on the vapor production output of the devices but not on the water production from devices. So, the focus on device-based water production and the associated cost of the water produced is essential. This article articulates the strategies and various scalable and efficient devices for evaporation-based solar-driven desalination. This article will be helpful for the researchers in improving devices output and coming up with a sustainable desalination and water treatment.

Novel and efficient Bi-doped CoTe nano-solar evaporators embedded on leno weave cotton gauze for efficient solar-driven desalination

Solar-driven desalination is considered an alternative to the conventional desalination due to its nearly zero carbon footprint and ease of operating in remote areas. Water can be purified wherever sunlight is available, providing a viable solution to water shortage. Metal chalcogenide-based materials are revolutionary for solar evaporators due to their excellent photothermal conversion efficiency, facile synthesis methods, stability, and low cost. Herein we present a prototype Bi-doped CoTe nano-solar evaporator embedded on leno weave cotton gauze (Bi/CoTe@CG) using the sonication process. The nano-solar evaporator was synthesized using a simple hydrothermal approach to provide an opportunity to scale up. The as designed solar evaporator consisting of 5 % Bi/CoTe@CG showed an excellent water flux of 2.38 kg m-2 h-1 upon one sun radiation (1 kW m-2), considered among the highest literature-reported values. The introduced solar evaporator showed excellent solar efficiency of 96.7 %, good stability, and reusability for five cycles of one hour. The best doping ratio of Bi in CoTe was obtained as Bi0.5Co9.5Te with a contact angle of 11.9° in powder form. The hydrophilic nature of the designed solar-evaporator increased the water interaction with the embedded nano-solar evaporator, which helps the transfer of the heat to nearby water molecules, break their hydrogen bonding and increase the evaporation rate. The ion concentration, of the desalinated pure water collected using Bi/CoTe@CG, decreased by many orders of magnitude and it is far below the limit of WHO standards for Na+ and K+. Thus, a self-floating Bi-doped CoTe nano-solar evaporator deposited on cotton gauze (CG) is an excellent solar evaporator for seawater desalination. The proposed solar evaporator is another step towards introducing environmentally friendly desalination methods.

Highly Aligned Graphene Aerogels for Multifunctional Composites

Stemming from the unique in-plane honeycomb lattice structure and the sp2 hybridized carbon atoms bonded by exceptionally strong carbon-carbon bonds, graphene exhibits remarkable anisotropic electrical, mechanical, and thermal properties. To maximize the utilization of graphene's in-plane properties, pre-constructed and aligned structures, such as oriented aerogels, films, and fibers, have been designed. The unique combination of aligned structure, high surface area, excellent electrical conductivity, mechanical stability, thermal conductivity, and porous nature of highly aligned graphene aerogels allows for tailored and enhanced performance in specific directions, enabling advancements in diverse fields. This review provides a comprehensive overview of recent advances in highly aligned graphene aerogels and their composites. It highlights the fabrication methods of aligned graphene aerogels and the optimization of alignment which can be estimated both qualitatively and quantitatively. The oriented scaffolds endow graphene aerogels and their composites with anisotropic properties, showing enhanced electrical, mechanical, and thermal properties along the alignment at the sacrifice of the perpendicular direction. This review showcases remarkable properties and applications of aligned graphene aerogels and their composites, such as their suitability for electronics, environmental applications, thermal management, and energy storage. Challenges and potential opportunities are proposed to offer new insights into prospects of this material.

Super-hydrophilic LaCoO3/g-C3N4 nanocomposite coated beauty sponge for solar-driven seawater desalination with simultaneous volatile organic compound removal

Interfacial solar steam generation (ISSG) is emerging as a promising, environment-friendly solution for fulfilling freshwater and energy demands. However, a critical challenge for ISSG lies in the presence of harmful volatile organic compounds (VOCs) in the feedwater which are co-evaporated with water, leading to more enriched concentration in condensed water. Herein, lanthanum cobaltate-graphitic carbon nitride (LaCoO3/g-C3N4, LCO/g-CN) nanocomposite decorated beauty sponge (LCO/g-CN@BS) is proposed as an efficient photothermal/photocatalytic material for solar-driven seawater desalination and simultaneous VOC degradation. The hydrophobic surface of the beauty sponge after LCO/g-CN coating becomes super-hydrophilic, ensuring sufficient water supply and our LCO/g-CN@BS delivers an evaporation rate of 1.94 kg m-2 h-1 under 1 sun irradiation. This LCO/g-CN@BS shows excellent seawater desalination capacity with a self-cleaning ability when employed for saltwater purification for a salt (NaCl) concentration as high as 15 wt%. Moreover, fast photocarrier transfer between LCO and g-CN leads to enhanced photocatalytic degradation of over 90% of phenol simultaneously, which is about 60% for only an LCO-based beauty sponge. This work presents a promising approach to combining novel nanocomposites with microporous structures for efficient solar desalination, offering simultaneous VOC degradation.

Hanging Photothermal Fabric Based on Polyaniline/Carbon Nanotubes for Efficient Solar Water Evaporation

Solar-driven water evaporation is essential to provide sustainable and ecofriendly sources of fresh water. However, there are still great challenges in preparing materials with broadband light absorption for high photothermal efficiency as well as in designing devices with large evaporation areas and small heat dissipation areas to boost the water evaporation rate. We designed a hanging-mode solar evaporator based on the polyaniline/carbon nanotube (PANI/CNT) fabric, in which the photothermal fabric acts as the solar evaporator and the micropores on the cotton fabric act as the water transfer channels. The hanging mode provides efficient evaporation at both interfaces by greatly reducing the heat dissipation area. The hanging mode PANI/CNT fabric solar evaporator can achieve an evaporation rate of 2.81 kg·m-2·h-1 and a photothermal efficiency of 91.74% under a solar illumination of 1 kW·m-2. This high-performance evaporator is designed by regulating the photothermal material and evaporation device, which provides a novel strategy for sustainable desalination.

Pickering Emulsion Templated 3D Cylindrical Open Porous Aerogel for Highly Efficient Solar Steam Generation

Porous-structured evaporators have been fabricated for achieving a high clean water throughput due to their maximized surface area. However, most of the evaporation surfaces in the porous structure are not active because of the trapped vapor in pores. Herein, a three-dimensional (3D) cylindrical aerogel-based photothermal evaporator with a disordered interconnected hierarchical porous structure is developed via a Pickering emulsion-involved polymerization method. The obtained cotton cellulose/aramid nanofibers/polypyrrole (CAP) aerogel-based evaporator achieved all-cold evaporation under 1.0 sun irradiation, which not only completely eliminated energy loss via radiation, convection, and conduction, but also harvested massive extra energy from the surrounding environment and bulk water, thus significantly increasing the total energy input for vapor generation to deliver an extremely high evaporation rate of 5.368 kg m-2 h-1 . In addition, with the external convective flow, solar steam generation over the evaporator can be dramatically enhanced due to fast vapor diffusion out of its unique opened porous structure, realizing an ultrahigh evaporation rate of 18.539 kg m-2 h-1 under 1.0 sun and 4.0 m s-1 . Moreover, this evaporator can continuously operate with concentrated salt solution (20 wt.% NaCl). This work advances rational design and construction of solar evaporator to promote the application of solar evaporation technology in freshwater production.

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

Photothermal regulation concerning solar harvesting and repelling has recently attracted significant interest due to the fast-growing research focus in the areas of solar heating for evaporation, photocatalysis, motion, and electricity generation, as well as passive cooling for cooling textiles and smart buildings. The parallel development of photothermal regulation strategies through both material and system designs has further improved the overall solar utilization efficiency for heating/cooling. In this review, we will review the latest progress in photothermal regulation, including solar heating and passive cooling, and their manipulating strategies. The underlying mechanisms and criteria of highly efficient photothermal regulation in terms of optical absorption/reflection, thermal conversion, transfer, and emission properties corresponding to the extensive catalog of nanostructured materials are discussed. The rational material and structural designs with spectral selectivity for improving the photothermal regulation performance are then highlighted. We finally present the recent significant developments of applications of photothermal regulation in clean energy and environmental areas and give a brief perspective on the current challenges and future development of controlled solar energy utilization.

Ethyl cellulose composite membranes containing a 2D material (MoS2) and helical carbon nanotubes for efficient solar steam generation and desalination

With the increasing water consumption, water evaporators have been investigated for clean water production. Herein, the fabrication of electrospun composite membrane evaporators based on ethyl cellulose (EC), with the incorporation of light-absorption enhancers 2D MoS₂ and helical carbon nanotubes, for steam generation and solar desalination is described. Under natural sunlight, the maximum water evaporation rate was 2.02 kg m^-2 h^-1 with an evaporation efficiency of 93.2 % (1 sun) and reached 2.42 kg m^-2 h^-1 at 12:00 pm (1.35 sun). The composite membranes demonstrated self-floating on the air-water interface and minimal accumulation of superficial salt during the desalination process due to the hydrophobic character of EC. For concentrated saline water (21 wt% NaCl), the composite membranes maintained a relatively high evaporation rate of up to ~79 % compared to the freshwater evaporation rate. The composite membranes are robust due to the thermomechanical stability of the polymer even while operating under steam-generating conditions. Over repeated use, they exhibited excellent reusability with a relative water mass change of >90 % compared to the first evaporation cycle. Moreover, desalination of artificial seawater produced a lower cation concentration (~3-5 orders of magnitude) and thereby yielded potable water, indicating the potential for solar-driven freshwater generation.

Multifunctional MoSe2 @MXene Heterostructure-Decorated Cellulose Fabric for Wearable Thermal Therapy

A booming demand for wearable electronic devices urges the development of multifunctional smart fabrics. However, it is still facing a challenge to fabricate multifunctional smart fabrics with satisfactory mechanical property, excellent Joule heating performance, highly efficient photothermal conversion, outstanding electromagnetic shielding effectiveness, and superior anti-bacterial capability. Here, a MoSe₂ @MXene heterostructure-based multifunctional cellulose fabric is fabricated by depositing MXene nanosheets onto cellulose fabric followed by a facile hydrothermal method to grow MoSe₂ nanoflakes on MXene layers. A low-voltage Joule heating therapy platform with rapid Joule heating response (up to 230 °C in 25 s at a supplied voltage of 4 V) and stable performance under repeated bending cycles (up to 1000 cycles) is realized. Besides, the multifunctional fabric also exhibits excellent photothermal performance (up to 130 °C upon irradiation for 25 s with a light intensity of 400 mW cm^-2 ), outstanding electromagnetic interference shielding effectiveness (37 dB), and excellent antibacterial performances (>90% anti-bacterial rate toward Escherichia coli, Bacillus subtilis, and Staphylococcus aureus). This work offers an efficient avenue to fabricate multifunctional wearable thermal therapy devices for mobile healthcare and personal thermal management.

Robust, Scalable, and Cost-Effective Surface Carbonized Pulp Foam for Highly Efficient Solar Steam Generation

Recently, a solar-driven evaporator has been applied in seawater desalination, but the low stability, high cost, and complex fabrication limit its further application. Herein, we report a novel, low-cost, scalable, and easily fabricated pulp-natural rubber (PNR) foam with a unique porous structure, which was directly used as a solar-driven evaporator after facile surface carbonization. This surface carbonized PNR (CPNR) foam without interface adhesion or modification was composed of a top photothermal layer with light absorption ability and a bottom hydrophilic foam layer with a porous and interconnected network structure. Due to the strong light absorption ability (93.2%) of the carbonized top layer, together with the low thermal conductivity (0.1 W m K^-1) and good water adsorption performance (9.9 g g^-1) of the bottom layer, the evaporation rate and evaporation efficiency of the pulp foam evaporator under 1 sun of illumination attained 1.62 kg m^-2 h^-1 and 98.09%, respectively, which were much higher than those of most cellulose-based solar-driven evaporators. Furthermore, the CPNR foam evaporator with high cost-effectiveness presented high light-thermal conversion, heat localization, and good salt rejection properties due to the unique porous structure. Additionally, the CPNR foam evaporator exhibited potential applications in the treatments of simulated sewage, metal ion concentration, and seawater desalination. Its cost-effectiveness was clearly higher than that of most reported evaporators as well. Therefore, this novel, low-cost, and stable pulp foam evaporator demonstrated here can be a very promising solution for water desalination and purification.

A robust and 3D-printed solar evaporator based on naturally occurring molecules

The interfacial solar desalination has been considered a promising method to address the worldwide water crisis without sophisticated infrastructures and additional energy consumption. Although various advanced solar evaporators have been developed, their practical applications are still restricted by the unsustainable materials and the difficulty of precise customization for structure to escort high solar-thermal efficiency. To address these issues, we employed two kinds of naturally occurring molecules, tannic acid and iron (III), to construct a low-cost, highly efficient and durable interfacial solar evaporator by three-dimensional (3D) printing. Based on a rational structural design, a robust and 3D-printed evaporator with conical array surface structure was developed, which could promote the light harvesting capacity significantly via the multiple reflections and anti-reflection effects on the surface. By optimizing the height of the conical arrays, the 3D-printed evaporator with tall-cone structure could achieve a high evaporation rate of 1.96 kg m^-2 h^-1 under one sun illumination, with a photothermal conversion efficiency of 94.4%. Moreover, this evaporator was also proved to possess excellent desalination performance, recycle stability, anti-salt property, underwater oil resistance, as well as adsorption capacity of organic dye contaminants for multipurpose water purification applications. It was believed that this study could provide a new strategy to fabricate low-cost, structural regulated solar evaporators for alleviating the dilemma of global water scarcity using abundant naturally occurring building blocks.

Facile Synthesis of Vertically Arranged CNTs for Efficient Solar-Driven Interfacial Water Evaporation

Solar-driven evaporation of water is a sustainable and promising technology for addressing the crisis of clean water. Herein, novel vertically arranged carbon nanotube (V-CNT) aerogels with a tree branch structure is facilely synthesized through an ice templating method. The V-CNT-based photothermal evaporator exhibits efficient broadband light trapping and super-hydrophilicity. Owing to the unique structure and ultrafast water transportation, a high evaporation rate of 3.26 kg m-2 h-1 was achieved by the three-dimensional V-CNT-based evaporator under a solar illumination of 1 kW m-2. More significantly, the V-CNT shows excellent recycling stability and salt-resistant performance in seawater and may provide a novel strategy to the practical sustainable technique of water purification applications.

A novel, flexible porous nanofibrous hydrogel interfacial solar evaporator for highly efficient seawater and wastewater purification

Solar desalination is recognized as one of the eco-friendly and sustainable ways to alleviate the global freshwater crisis but still requires further research, especially in developing high-performance evaporators. Herein, we prepared an efficient carbon nanotubes (CNTs)@polyvinyl alcohol (PVA) nanofibrous hydrogel evaporator by electrospinning and subsequently chemical cross-linking treatment. Due to CNTs with good light absorption capacity, the evaporator exhibited an excellent light absorption capacity (>90%) throughout the full spectrum range (250-2500 nm). Meanwhile, the interconnected pores from electrospinning, as well as the intermediate water in the hydrogel, ensured the prepared evaporator with a favorable evaporation rate of up to 2.16 kg m^-2 h^-1 and photothermal conversion efficiency of ∼88.13% under one solar light intensity. For long-term seawater desalination, the CNTs@PVA nanofibrous hydrogel evaporator also presented superior salt resistance, durability and good self-cleaning properties. Besides, various non-volatile pollutants can be completely removed by the prepared evaporator during the wastewater purification. As a result, this work is considered to provide a new direction for developing high-performance evaporators to provide freshwater through seawater desalination and wastewater purification.

Recent Development of Carbon-Nanotube-Based Solar Heat Absorption Devices and Their Application

Population growth and the current global weather patterns have heightened the need to optimize solar energy harvesting. Solar-powered water filtration, electricity generation, and water heating have gradually multiplied as viable sources of fresh water and power generation, especially for isolated places without access to water and energy. The unique thermal and optical characteristics of carbon nanotubes (CNTs) enable their use as efficient solar absorbers with enhanced overall photothermal conversion efficiency under varying solar light intensities. Due to their exceptional optical absorption efficiency, low cost, environmental friendliness, and natural carbon availability, CNTs have attracted intense scientific interest in the production of solar thermal systems. In this review study, we evaluated CNT-based water purification, thermoelectric generation, and water heating systems under varying solar levels of illumination, ranging from domestic applications to industrial usage. The use of CNT composites or multilayered structures is also reviewed in relation to solar heat absorber applications. An aerogel containing CNTs was able to ameliorate water filtering performance at low solar intensities. CNTs with a Fresnel lens improved thermoelectric output power at high solar intensity. Solar water heating devices utilizing a nanofluid composed of CNTs proved to be the most effective. In this review, we also aimed to identify the most relevant challenges and promising opportunities in relation to CNT-based solar thermal devices.

Bio-Derived Photothermal Materials and Evaporators for Sustainable Solar Energy-Driven Water Process

Interfacial solar steam generation (ISSG) is considered as an excellent seawater desalination technology because of its electricity-independent nature, low cost, and portability. However, improving the water evaporation efficiency, simplifying the fabrication process, and reducing the overall cost of the evaporator are still challenging. Here, an efficient and sustainable solar water evaporator is fabricated with carbonized ginkgo biloba leaves as the structural basis of photothermal materials. The combination of the abundant capillary channels in ginkgo leaves paired with polyacrylamide (PAM) hydrogel accelerates water transportation and solar-driven evaporation. The fabricated evaporator shows excellent photothermal conversion capability and evaporates water at 2.39 kg m^-2 h^-1 under 1 sun irradiation. In addition, the device exhibits remarkable stability in simulated seawater and can effectively realize seawater desalination or sewage treatment. As a result, the system is promising for future highly efficient solar evaporation due to its environmental protection and low cost.

Inhibition of Phenol from Entering into Condensed Freshwater by Activated Persulfate during Solar-Driven Seawater Desalination

Recently, solar-driven seawater desalination has received extensive attention since it can obtain considerable freshwater by accelerating water evaporation at the air-water interface through solar evaporators. However, the high air-water interface temperature can cause volatile organic compounds (VOCs) to enter condensed freshwater and result in water quality safety risk. In this work, an antioxidative solar evaporator, which was composed of MoS₂ as the photothermal material, expandable polyethylene (EPE) foam as the insulation material, polytetrafluoroethylene (PTFE) plate as the corrosion resistant material, and fiberglass membrane (FB) as the seawater delivery material, was fabricated for the first time. The activated persulfate (PS) methods, including peroxymonosulfate (PMS) and peroxodisulfate (PDS), were applied to inhibit phenol from entering condensed freshwater during desalination. The distillation concentration ratio of phenol (R_D) was reduced from 76.5% to 0% with the addition of sufficient PMS or PDS, which means that there was no phenol in condensed freshwater. It was found that the Cl^- is the main factor in activating PMS, while for PDS, light, and heat are the dominant. Compared with PDS, PMS can make full utilization of the light, heat, Cl^- at the evaporator's surface, resulting in more effective inhibition of the phenol from entering condensed freshwater. Finally, though phenol was efficiently removed by the addition of PMS or PDS, the problem of the formation of the halogenated distillation by-products in condensed freshwater should be given more attention in the future.

3D macroporous CUPC/g-C3N4 heterostructured composites for highly efficient multifunctional solar evaporation

Solar-driven interfacial evaporation is a promising technology for water recycling and purification. A sustainable solar evaporation material should have not only high photothermal conversion efficiency, but also an ecofriendly fabrication process as well as pollutant degradation and sterilization properties. We present in this work a solar evaporator based on graphitic carbon nitride (g-C₃N₄) and copper phthalocyanine (CUPC) composites with typical type-I heterojunctions. Superhydrophilic three-dimensional macroporous g-C₃N₄ was obtained by self-assembly of precursors in aqueous solution followed by thermal polycondensation. By adding various weight ratios (0.15%, 1.5% and 7.5%) of CUPC, the composites exhibited a strong absorption in the region of red and infrared light. The CUPC-CN 7.5% composite achieved a photothermal conversion efficiency of 98.5% in nanofluids with an interfacial solar evaporation efficiency of 93.6% for artificial sea water and 98.7% for deionized water, which are among the highest reported to date. Besides, the composite materials demonstrated superior water purification capabilities by decomposing dye molecules and E. coli bacteria in aqueous solution. Our work established a novel approach for the development of multifunctional interfacial evaporators based on macroporous organic semiconductor heterostructures.

3D Hydrogel Evaporator with Vertical Radiant Vessels Breaking the Trade-Off between Thermal Localization and Salt Resistance for Solar Desalination of High-Salinity

Delivering sufficient water to the evaporation surface/interface is one of the most widely adopted strategies to overcome salt accumulation in solar-driven interfacial desalination. However, water transport and heat conduction loss are positively correlated, resulting in the trade-off between thermal localization and salt resistance. Herein, a 3D hydrogel evaporator with vertical radiant vessels is prepared to surmount the long-standing trade-off, thereby achieving high-rate and stable solar desalination of high-salinity. Experiments and numerical simulations reveal that the unique hierarchical structure, which consists of a large vertical vessel channel, radiant vessels, and porous vessel walls, facilitates strong self-salt-discharge and low longitudinal thermal conductivity. With the structure employed, a groundbreaking comprehensive performance, under one sun illumination, of evaporation rate as high as 3.53 kg m^-2  h^-1 , salinity of 20 wt%, and a continuous 8 h evaporation is achieved, which thought to be the best reported result from a salt-free system. This work showcases the preparation method of a novel hierarchical microstructure, and also provides pivotal insights into the design of next-generation solar evaporators of high-efficiency and salt tolerance.

Integrating a Self-Floating Janus TPC@CB Sponge for Efficient Solar-Driven Interfacial Water Evaporation

Solar-driven photothermal interfacial evaporation is considered as one of the most promising strategies in seawater desalination and wastewater treatment. In desalination, evaporation efficiency and salt resistance are regarded as two inter-constraint measures. Thus, it is still challenging to fabricate solar evaporators with both high evaporation efficiency and excellent salt resistance. In the present work, a self-floating Janus sponge composed of hydrophobic carbon black (CB) coating and hydrophilic porous thermoplastic polyurethane-carbon nanotube (TPC) nanofibrous substrate (TPC@CB) is fabricated via a simple electrospinning and gas templating expansion method. Attributing to the unique trilaminar functional architecture: the upper superhydrophobic solar-absorption coating, the intermediate ultrathin heat localization layer, and the lower cellular thermal insulation layer, the Janus TPC@CB sponge exhibits high evaporation efficiency (1.80 kg m^-2 h^-1 with an energy efficiency of 97.2% under 1.0 solar irradiation) and outstanding salt resistance ability. Moreover, zero liquid discharge in salt-containing wastewater treatment is realized using the Janus TPC@CB sponge as a solar-driven photothermal medium. This work provides a promising approach to seawater desalination and wastewater treatment.

Hydrophobic and porous carbon nanofiber membrane for high performance solar-driven interfacial evaporation with excellent salt resistance

Interfacial evaporation has recently received great interest from both academia and industry to harvest fresh water from seawater, due to its low cost, sustainability and high efficiency. However, state-of-the-art solar absorbers usually face several issues such as weak corrosion resistance, salt accumulation and hence poor long-term evaporation stability. Herein, a hydrophobic and porous carbon nanofiber (HPCNF) is prepared by combination of the porogen sublimation and fluorination. The HPCNF possessing a macro/meso porous structure exhibits large contact angles (as high as 145°), strong light absorption and outstanding photo-thermal conversion performance. When the HPCNF is used as the solar absorber, the evaporation rate and efficiency can reach up to 1.43 kg m^-2h^-1 and 87.5% under one sunlight irradiation, respectively. More importantly, the outstanding water proof endows the absorber with superior corrosion resistance and salt rejection performance, and hence the interfacial evaporation can maintain a long-term stability and proceed in a variety of complex conditions. The HPCNFs based interfacial evaporation provides a new avenue to the high efficiency solar steam generation.

Measurement of the Photothermal Conversion Efficiency of CNT Films Utilizing a Raman Spectrum

Because carbon nanotube (CNT) films have high photothermal conversion efficiency (PTCE), they have been widely used in bolometric and photothermoelectric photodetectors, seawater desalination, and cancer therapy. Here, we present a simple, quick, and non-destructive method to measure the PTCE of CNT films. According to the linear relationship between the Raman shift of the G⁺ peak and the temperature of a CNT, the offset of the G⁺ peak under varying excitation light power can characterize the changed temperature. Combining the simulation of the temperature distribution, the final value of the PTCE can be obtained. Finally, a CNT film with a high PTCE was chosen to be fabricated as a bolometric photodetector; a quite high responsivity (2 A W⁻¹ at 532 nm) of this device demonstrated the effectiveness of our method.

Hierarchically Designed Three-Dimensional Composite Structure on a Cellulose-Based Solar Steam Generator

The emerging water purification technology represented by solar water evaporation has developed rapidly in recent years and is widely used in seawater desalination. However, the high reflectivity of sunlight and low efficiency of photothermal conversion greatly hinder its application prospects. In this paper, the hierarchical structure of the film was designed and optimized by the addition of carbon materials in the process of bacterial cellulose culture. A cellulose-based composite film material with a microporous structure was obtained, which can improve the photothermal evaporation rate and photothermal conversion efficiency from the structural principle to improve the stability of floating on the water. Bacterial cellulose (BC) as a three-dimensional carrier was combined with one-dimensional and two-dimensional (1D/2D) compounds of carbon nanotubes (CNT) and reduced graphene oxide (RGO) to form composite films for solar evaporation. By the addition of CNT-RGO (21.8 wt %), the composite showed prominent photothermal evaporation rate and photothermal conversion efficiency properties. Through in situ culture of BC, not only a tight structure can be obtained but also the surface of BC contains a large number of hydroxyl groups, which have many active sites to load photothermal materials. BC nanofibers, CNT, and RGO cooperate to form a porous network structure, which provides continuous double channels for the rapid transmission of water molecules and light paths, so as to form an excellent photothermal layer. The photothermal conversion efficiency is 90.2%, and the photothermal evaporation rate is 1.85 kg m^-2 h^-1 to achieve efficient solar interface evaporation. This is a high level of photothermal properties in a cellulose-based solar steam generator. The superior photothermal performance of this hybrid film possesses scalability and desalination ability.

Melamine/Silicone Hybrid Sponges with Controllable Microstructure and Wettability for Efficient Solar-Driven Interfacial Desalination

Solar-driven interfacial evaporation (SIE) has received extensive attention as a very promising desalination technique to solve the fresh water shortage crisis. However, evaporation rate decline and salt-fouling during long-term SIE seriously hinder applications of solar evaporators. Here, we report the preparation of melamine/silicone (MS) hybrid sponges with controllable microstructure and wettability for efficient SIE by further combination with carbon nanotubes (CNTs). The MS sponges are synthesized by hydrolytic condensation and phase separation of two silanes in the melamine sponge. The microstructure and wettability of the MS sponges are highly controllable by the silanes concentration. The CNTs@MS solar evaporators have a unique three-tier hierarchical macro-/micro-/nanostructure, very low thermal conductivity as well as a superhydrophilic hull and a superhydrophobic nucleus. Consequently, the CNTs@MS solar evaporators show a highly stable evaporation rate of ∼1.75 kg m^-2 h^-1 without any salt precipitation during a long-term cyclic solar desalination of 3.5 wt % NaCl solution under 1 sun illumination. Furthermore, salt precipitation is completely hindered even during SIE of 20 wt % NaCl solution under 1 sun. The CNTs@MS solar evaporators are very promising for practical SIE because of their excellent performance and simple preparation method.

Forest-like Laser-Induced Graphene Film with Ultrahigh Solar Energy Utilization Efficiency

To achieve high solar energy utilization efficiency, photothermal materials with broadband absorption of sunlight and high conversion efficiency are becoming a fast-growing research focus. Inspired by the forest structure with efficient sunlight utilization, we designed and fabricated a graphene film consisting of densely arranged porous graphene though laser scribing on polybenzoxazine resin (poly(Ph-ddm)). This hierarchical structure significantly reduced the light reflection of graphene as a 2D material. With a combination of advanced photothermal conversion properties of graphene, the 3D structured graphene film, named forest-like laser-induced graphene (forest-like LIG), was endowed with a very high light absorption of 99.0% over the whole wavelength range of sunlight as well as advanced light-to-heat conversion performance (reaching up to 87.7 °C within 30 s under the illumination of simulated sunlight and showing an equilibrium temperature of 90.7 ± 0.4 °C). As a further benefit of its superhydrophobicity, a photothermal actuator with quick actuated response and high motion velocity, as well as a solar-driven interfacial desalination membrane with durable salt-rejecting properties and high solar evaporation efficiencies, was demonstrated.

Nature Inspired MXene-Decorated 3D Honeycomb-Fabric Architectures Toward Efficient Water Desalination and Salt Harvesting

The 3D honeycomb-like fabric decorated with MXene is woven as solar evaporator. The honeycomb structure enables light-trapping and recycling of convective and radiative heat. The 3D honeycomb-fabric evaporator possesses high solar efficiency up to 93.5% under 1 sun irradiation and excellent salt harvesting ability.

ABSTRACT

Solar steam generation technology has emerged as a promising approach for seawater desalination, wastewater purification, etc. However, simultaneously achieving superior light absorption, thermal management, and salt harvesting in an evaporator remains challenging. Here, inspired by nature, a 3D honeycomb-like fabric decorated with hydrophilic Ti₃C₂T_x (MXene) is innovatively designed and successfully woven as solar evaporator. The honeycomb structure with periodically concave arrays creates the maximum level of light-trapping by multiple scattering and omnidirectional light absorption, synergistically cooperating with light absorbance of MXene. The minimum thermal loss is available by constructing the localized photothermal generation, contributed by a thermal-insulating barrier connected with 1D water path, and the concave structure of efficiently recycling convective and radiative heat loss. The evaporator demonstrates high solar efficiency of up to 93.5% and evaporation rate of 1.62 kg m⁻² h⁻¹ under one sun irradiation. Moreover, assisted by a 1D water path in the center, the salt solution transporting in the evaporator generates a radial concentration gradient from the center to the edge so that the salt is crystallized at the edge even in 21% brine, enabling the complete separation of water/solute and efficient salt harvesting. This research provides a large-scale manufacturing route of high-performance solar steam generator. [Image: see text]

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40820-021-00748-7.

Programmable Asymmetric Nanofluidic Photothermal Textile Umbrella for Concurrent Salt Management and In Situ Power Generation During Long-Time Solar Steam Generation

Although solar-driven seawater desalination affords a highly promising strategy for freshwater-electricity harvesting by employing abundant solar energy and ocean resources, the inevitable salt crystallization on the surface of evaporators causes a sharp decline in evaporation performance and the poor electricity output of most coupled inflexible evaporation-power generation devices limits the scalability and durability in long-time practical applications. Herein, we report a simple programmable nanofluidic photothermal textile umbrella by asymmetrically depositing MoS₂ nanosheets on cotton textiles, which allows for controllable gravity-assisted edge-preferential salt crystallization/harvesting via self-manipulated saline solution transportation in the wet umbrella and simultaneous drenching-induced electrokinetic voltage generation (0.535 V)/storage (charging a capacitor to 12.2 V) in over 120 h of the nonstop solar desalination process (with 7.5 wt % saline solution). Notably, the morphology and salt crystallization areas can be managed via the programmed umbrellas. Moreover, the asymmetric textile umbrellas possess admirable sewable features for large-scale integration to enhance the evaporation and voltage output efficiency. Importantly, this textile umbrella evaporator shows excellent output stability and durability even after 40 times of washing. This work may pave a scalable way to design programmable solar evaporators for sustainable seawater desalination with scalabilities of zero-waste discharge, valuable resource recovery, and energy harvesting.

Low-Cost, Unsinkable, and Highly Efficient Solar Evaporators Based on Coating MWCNTs on Nonwovens with Unidirectional Water-Transfer

Solar vapor generation technology is promising in seawater desalination, sewage purification, and other fields. However, wide application of this technology is still largely confined due to its high cost and difficulties for scalable production. In this study, an ever-floating solar evaporator is fabricated by coating multiwall carbon nanotubes on a bicomponent nonwoven composed of polypropylene/polyethylene core-sheath fibers. This all-fiber structure is highly porous and ultralight, with large specific area (for efficient water evaporation), interconnected channels (for easy vapor escape), and low thermal conductivity (to avoid heat loss). The unique unidirectional water-transfer behavior of the nonwoven enables it to spontaneously pump an adjustable amount of water for interfacial solar heating and a delicate balance between water supply and loss may accelerate the evaporation speed of water. These distinct benefits endow the solar evaporator with excellent evaporation rates of 1.44 kg m^-2  h^-1 under the simulated irradiation of 1 sun and 12.81 kg m^-2  d^-1 under natural sunlight. Moreover, the evaporator can be fabricated by using low-cost materials and industrialized methods (overall cost ≈2.4 USD m^-2 ), making one believe its practical significance for commercial solar steam evaporation.

Distinct Roles of Tensile and Compressive Stresses in Graphitizing and Properties of Carbon Nanofibers

It is generally accepted that inducing molecular alignment in a polymer precursor via mechanical stresses influences its graphitization during pyrolysis. However, our understanding of how variations of the imposed mechanics can influence pyrolytic carbon microstructure and functionality is inadequate. Developing such insight is consequential for different aspects of carbon MEMS manufacturing and applicability, as pyrolytic carbons are the main building blocks of MEMS devices. Herein, we study the outcomes of contrasting routes of stress-induced graphitization by providing a comparative analysis of the effects of compressive stress versus standard tensile treatment of PAN-based carbon precursors. The results of different materials characterizations (including scanning electron microscopy, Raman and X-ray photoelectron spectroscopies, as well as high-resolution transmission electron microscopy) reveal that while subjecting precursor molecules to both types of mechanical stresses will induce graphitization in the resulting pyrolytic carbon, this effect is more pronounced in the case of compressive stress. We also evaluated the mechanical behavior of three carbon types, namely compression-induced (CIPC), tension-induced (TIPC), and untreated pyrolytic carbon (PC) by Dynamic Mechanical Analysis (DMA) of carbon samples in their as-synthesized mat format. Using DMA, the elastic modulus, ultimate tensile strength, and ductility of CIPC and TIPC films are determined and compared with untreated pyrolytic carbon. Both stress-induced carbons exhibit enhanced stiffness and strength properties over untreated carbons. The compression-induced films reveal remarkably larger mechanical enhancement with the elastic modulus 26 times higher and tensile strength 2.85 times higher for CIPC compared to untreated pyrolytic carbon. However, these improvements come at the expense of lowered ductility for compression-treated carbon, while tension-treated carbon does not show any loss of ductility. The results provided by this report point to the ways that the carbon MEMS industry can improve and revise the current standard strategies for manufacturing and implementing carbon-based micro-devices.

Unidirectionally Driving Nanofluidic Transportation via an Asymmetric Textile Pump for Simultaneous Salt-Resistant Solar Desalination and Drenching-Induced Power Generation

Solar-driven seawater desalination provides a promising technology for sustainable water energy harvesting. Although tremendous efforts have been dedicated to developing efficient evaporators, the challenge of preventing salt accumulation while simultaneously realizing high-performance steam-electricity cogeneration remains to be addressed. In this work, inspired by the water and solute transportation in plants via the wicking mechanism, a one-way asymmetric nanofluidic photothermal evaporator fabricated by disproportionately depositing photothermal MXene nanosheets on a hydrophilic cotton textile is reported for simultaneous freshwater and power production. By unidirectionally driving dynamic saline transportation via this photothermal cotton textile pump, this evaporator not only enables self-operating salt rejection for stable steam generation but also affords continuous electric power generation induced by the formation of an asymmetric double electrode layer within MXene nanochannels under the drenching state. Specifically, the solar-driven evaporation rate and voltage generation reach 1.38 kg/m²/h (with a conversion efficiency of 83.1%) and 363 mV under 1 sun irradiation, respectively. Notably, this designed nanofluidic system suffers negligible performance depreciation after 30 h of operation and washing 15 times, which indicates its outstanding stability and reusability. This facile design of the asymmetric nanofluidic photothermal system may provide prospective opportunities for scaling up sustainable freshwater and electric power production.

Carbon nanomaterials treated by combination of oxidation and flash for highly efficient solar water evaporation

The high-efficiency solar evaporation is a potential technique to desalinate hypersaline wastewater and seawater to alleviate the global fresh water shortage. Photo-thermal agent and solar evaporator with low-cost raw materials, high photo-thermal conversion efficiency and simple-fast preparation methods is crucial to realize the industrial application of solar evaporation. Herein, carbon nanomaterial with higher light absorption and photo-thermal conversion efficiency than that of carbon black was obtained by combination treatment of carbon black with oxidation and flash illumination. In order to characterize the evaporation performance of the devices, a floating evaporator was fabricated with the carbon nanomaterial on the top of polyethylene foam wrapped with non-woven fabrics. The evaporation rate and photo-thermal conversion efficiency of evaporators were affected significantly by environmental temperature and humidity. At the environmental temperature of 19.5 °C, the evaporator fabricated with the combined treated carbon nanomaterial as photo-thermal agents presents a stable evaporation rate at 1.27 kg m^-2 h^-1 and solar evaporation efficiency at 78.7% under 1 kW m^-2 simulated sun illumination, which are higher than those of evaporator with carbon black (1.13 kg m^-2 h^-1 and 68.1%). The distilled water obtained from the solar evaporator met the standards of drinkable water. Overall, the experimental result demonstrates a great promise application of treated carbon nanomaterial as a photo-thermal agent in the field of seawater desalination and solar-energy collector.

Multi-Channel Optical Device for Solar-Driven Bacterial Inactivation under Real-Time Temperature Feedback

Solar-driven photothermal antibacterial devices have attracted a lot of interest due to the fact that solar energy is one of the cleanest sources of energy in the world. However, conventional materials have a narrow absorbance band, resulting in deficient solar harvesting. In addition, lack of knowledge on temperature change in these devices during the photothermal process has also led to a waste of energy. Here, we presented an elegant multi-channel optical device with a multilayer structure to simultaneously address the above-mentioned issues in solar-driven antibacterial devices. In the photothermal channel, semiconductor IrO₂ -nanoaggregates exhibited higher solar absorbance and photothermal conversion efficiency compared with nanoparticles. In the luminescence channel, thermal-sensitive Er-doped upconversion nanoparticles were utilized to reflect the microscale temperature in real-time. The bacteria were successfully inactivated during the photothermal effect under solar irradiation with temperature monitoring. This study could provide valuable insight for the development of smart photothermal devices for solar-driven photothermal bacterial inactivation in the future.

Interfacial solar vapor generation for desalination and brine treatment: Evaluating current strategies of solving scaling

Interfacial solar vapor generation, an efficient, sustainable, and low-cost method for producing clean water, has attracted great interest for application in solar desalination and wastewater treatment. Although recent studies indicated significant enhancement of overall performance by developing photothermal materials and constructing different dimensional systems, stable evaporation performance and long-term operation of the evaporator are hindered by severe scaling issues. In this critical review, we present the latest strategies in reducing salt accumulation on the evaporator for solar desalination and brine treatment. We first demonstrate the consequences of salt accumulation, and then discuss various self-cleaning methods based on bio-inspired concepts and other strategies such as physical cleaning, ion rejection and exchange, fast ion diffusion, and controlled crystallization, etc. Importantly, we discuss and address the rational design of the evaporator via establishing a relationship model between its porosity, thickness, and thermal conductivity. Lastly, we evaluate salt-resistance strategies, evaporation performance, and possibilities of real application in different evaporation systems with scaling-resistant abilities.

Hydrophilic 3D Interconnected Network of Bacterial Nanocellulose/Black Titania Photothermal Foams as an Efficient Interfacial Solar Evaporator

The design and development of scalable, efficient photothermal evaporator systems that reduce microplastic pollution are highly desirable. Herein, a sustainable bacterial nanocellulose (BNC)-based self-floating bilayer photothermal foam (PTF_b) is designed that eases the effective confinement of solar light for efficient freshwater production via interfacial heating. The sandwich nanoarchitectured porous bilayer solar evaporator consists of a top solar-harvesting blackbody layer composed of broad-spectrum active black titania (BT) nanoparticles embedded in the BNC matrix and a thick bottom layer of pristine BNC for agile thermal management, the efficient wicking of bulk water, and staying afloat. A decisive advantage of the BNC network is that it enables the fabrication of a lightweight photothermal foam with reduced thermal conductivity and high wet strength. Additionally, the hydrophilic three-dimensional (3D) interconnected porous network of BNC contributes to the fast evaporation of water under ambient solar conditions with reduced vaporization enthalpy by virtue of intermediated water generated via a BNC-water interaction. The fabricated PTF_b is found to yield a water evaporation efficiency of 84.3% (under 1054 W m^-2) with 4 wt % BT loading. Furthermore, scalable PTF_b realized a water production rate of 1.26 L m^-2 h^-1 under real-time conditions. The developed eco-friendly BNC-supported BT foams could be used in applications such as solar desalination, contaminated water purification, extraction of water from moisture, etc., and thus could address one of the major present-day global concerns of drinking water scarcity.

Flexible Transparent Polypyrrole-Decorated MXene-Based Film with Excellent Photothermal Energy Conversion Performance

Flexible transparent heaters based on photothermal energy conversion are highly desired for next-generation electronic devices. However, how to balance the photothermal conversion efficiency and transparency is still a huge challenge. In this work, we demonstrate a flexible polycarbonate (PC) film with balanced photothermal energy conversion performance and transparency obtained from the spraying polypyrrole (PPy)-modified Ti₃C₂T_x MXene (MXene@PPy) layer. Due to the synergistic light-to-heat effects of MXene and the attached PPy nanoparticles, the resulted transparent film heater (MP-PC) can obtain a satisfying photothermal conversion performance (47.5 °C at 100 mW/cm²) at a low spraying density of MXene and thus show an effective transmittance of 51.61%, simultaneously. Moreover, the photothermal conversion performance reveals an outstanding stability without significant deterioration after exposing to an outdoor environment for seven months. Besides, arising from the excellent surface electrical resistance (413 Ω/sq), the MP-PC film also exhibits an effective Joule heating capacity with a high heating temperature of 108 °C at 24 V input voltage. As one of the promising applications, the MP-PC film exhibits the effectiveness and feasibility as a light-triggered thermal therapy film for human skin in cold environments.