Floatable, Self-Cleaning, and Carbon-Black-Based Superhydrophobic Gauze for the Solar Evaporation Enhancement at the Air-Water Interface

Freshwater production via efficient oil-water separation and solar-assisted water evaporation using black titanium oxide nanoparticles

Fabrication of a multipurpose superhydrophobic mesh via modification of a galvanized steel mess using black titanium oxide nanoparticles and perfluorodecyltriethoxysilane is reported. Modified mesh exhibits superhydrophobicity with a water static contact angle of 157° ± 2 along with a tilt angle of 5° ± 1 and suitable chemical, thermal, mechanical stability, and self-cleaning ability. The droplet dynamic behavior of superhydrophobic mesh revels the impact velocity is 1.5 ms^-1 for splashing of the water droplet. The developed mesh is studied for freshwater generation from oily water and seawater via efficient oil-water separation and solar evaporation, respectively. A proficiency of 99% and 88% is achieved for oil-water separation from mixture and emulsion, respectively. Solar evaporation efficiency of 64% and 76% are recorded under low-intensity light (225 Wm^-2) and natural sunlight (591 Wm^-2), respectively, from distilled water. For seawater, the evaporation efficiency of 69% is achieved under natural sunlight. Present approach can be applied to any size and shape of the mesh and has great industrial applications.

High-Performance Salt-Rejecting and Cost-Effective Superhydrophilic Porous Monolithic Polymer Foam for Solar Steam Generation

Direct solar desalination with excellent solar photothermal efficiency, lower cost, and extended generator device lifetime is beneficial to increase potable water supplies. To address fundamental challenges in direct solar desalination, herein, we present a new and facile method for the scalable fabrication of the polymer porous foam (VMP) as salt-resistant photothermal materials, which was synthesized through a one-step hydrothermal method using styrene and 1-vinyl-3-ethylimidazolium tetrafluoroborate as monomers and N,N'-methylenebisacrylamide as the cross-linking agent. The as-resulted VMP shows excellent mechanical properties which could have a compression strain of 30%, resulting in its superior processability for practical operation. In addition, by taking advantage of its inherent low density, well-controlled porous structure (porosity is 73.81%), and extremely low thermal conductivity (0.03204 W m^-1 K^-1), the VMP exhibits an excellent solar evaporation property, and the solar photothermal efficiency can reach more than 88% under 1 kW m^-2 irradiation. Moreover, the introduction of ionic liquid moiety (imidazolium tetrafluoroborate) into VMP results in its interesting superhydrophilic wettability, which can accelerate water transportation (wetting in 5s) and resolve the crystalline salt within 1.13 h. In addition, the interconnected macropores of the VMP, as water channels, can replenish the vaporized brine on the surface to prevent salt from adhering. The VMP shows a salt-resistant performance, for example, its solar evaporation efficiency remains nearly unchanged after 6 h duration under 1 sun irradiation. Based on its simple and cost-effective manufacturing process, excellent solar photothermal efficiency, and salt resistance, our VMP may be a promising candidate as photothermal materials for practical desalination from seawater and other wastewater.

Flame Synthesis of Superhydrophilic Carbon Nanotubes/Ni Foam Decorated with Fe2O3 Nanoparticles for Water Purification via Solar Steam Generation

Solar-driven water evaporation has been proposed as a renewable and sustainable strategy for the generation of clean water from seawater or wastewater. To enable such technologies, development of photothermal materials that enable efficient solar steam generation is essential. The current challenge is to manufacture such photothermal materials cost-effectively and at scale. Furthermore, the photothermal materials should be strongly hydrophilic and environmentally stable. Herein, we demonstrate facile and scalable fabrication of carbon nanotube (CNT)-based photothermal nanocomposite foam by igniting an ethanol solution of ferric acetylacetonate [Fe(acac)₃] absorbed within nickel (Ni) foam under ambient conditions. The Fe(acac)₃ precursor provides carbon and the zero-valent iron catalyst for growing CNTs on the Ni foam, while ethanol facilitates the dispersion of Fe(acac)₃ on the Ni foam and supplies heat energy for the growth of CNTs by its burning. A forest of dense and uniform CNTs decorated with Fe₂O₃ nanoparticles is generated within seconds. The resultant Fe₂O₃/CNT/Ni nanocomposite foam exhibits "superhydrophilicity" and high light absorption capacity, ensuring rapid transport and fast evaporation of water within the entire foam. Efficient light-to-heat conversion causes the surface temperature of the foam to reach ∼83.1 °C under 1 sun irradiation. The average water evaporation rates of such foam are as high as ∼1.48 and ∼4.27 kg m^-2 h^-1 with light-to-heat conversion efficiencies of ∼81.3 and ∼93.8% under 1 sun and 3 sun irradiation, respectively. Moreover, the versatile and scalable combustion synthesis strategy presented here can be realized on various substrates, exhibiting high adaptability for different applications.

Self-Assembly of Carbon Black/AAO Templates on Nanoporous Si for Broadband Infrared Absorption

Broadband absorption in the mid-infrared region is of significance for wide applications, such as photo/thermal detection, infrared stealth, and thermal imaging. Recently, metal-based plasmonic absorbers have been developed in the mid-infrared region. However, the fabrication cost, thickness, and bandwidth of these absorbers applied in aerospace still need to be improved. In this study, we propose and experimentally demonstrate a large-area, rather thin, metal-free absorber with broadband mid-infrared absorption based on a low-cost self-assembly process. The metal-free absorber is fabricated by spraying carbon black nanoparticles onto 5 μm-thick transferrable anodic aluminum oxide (AAO) templates on nanoporous Si graded-index films, which are fabricated by ion irradiation. Experimental results show that the average absorbance can reach 97.5% in the range of 2.5-15.3 μm. Full-wave numerical simulations show that the electromagnetic fields are greatly enhanced into pores, as these random carbon black particles serve as scatter centers and couple light into 5 μm-thick AAO templates, enhancing the interaction of light with carbon black significantly, and reveal that the high-performance broadband absorption is attributed to the light-trapping effect. The significant light absorption combined with a low-cost, high-production self-assembly technique suggests that the absorber can be used in the fields of optoelectronics and integrated photonics.

3D-Structured Carbonized Sunflower Heads for Improved Energy Efficiency in Solar Steam Generation

Solar steam generation is regarded as a perspective technology, due to its potentials in solar light absorption and photothermal conversion for seawater desalination and water purification. Although lots of steam generation systems have been reported to possess high conversion efficiencies recently, researches of simple, cost-effective, and sustainable materials still need to be done. Here, inspired by natural young sunflower heads' property increasing the temperature of dish-shaped flowers by tracking the sun, we used 3D-structured carbonized sunflower heads as an effective solar steam generator. The evaporation rate and efficiency of these materials under 1 sun (1 kW m^-2) are 1.51 kg m^-2 h^-1 and 100.4%, respectively, beyond the theoretical limit of 2D materials. This high solar efficiency surpasses all other biomass-based materials ever reported. It is demonstrated that such a high capability is mainly attributed to the 3D-structured top surface, which could reabsorb the lost energy of diffuse reflection and thermal radiation, as well as provide enlarged water/air interface for steam escape. 3D-structured carbonized sunflower heads provide a new method for the future design and fabrication of high-performance photothermal devices.

Ultralight Biomass Porous Foam with Aligned Hierarchical Channels as Salt-Resistant Solar Steam Generators

The creation of solar steam generators with both high energy conversion efficiency and desired salt-resistant performance is essential for practical desalination. Herein, we report for the first time the fabrication of polypyrrole-coated biomass porous foam as efficient solar steam generators. The as-prepared foams possess a low thermal conductivity of 0.022 W M^-1 K^-1 for alkali-treated corn straw (CSA) and 0.027 W M^-1 K^-1 for both microwave- and alkali-treated corn straw (CSMA). Based on their high light absorption (95-100%), superhydrophilic wettability, excellent thermal insulation, and unique aligned channels, the foams show excellent energy conversion efficiency of 89.74, 91.08, and 91.54% for the polypyrrole-coated CSA (P-CSA) and 96.8, 97.05, and 98.32% for the polypyrrole coated CSMA (P-CSMA) at light intensities of 1, 2, and 3 kW m^-2, respectively. Importantly, thanks to their aligned hierarchical channels, our generators show extraordinary salt-resistant performance, e.g., the energy conversion efficiencies of P-CSA and P-CSMA were measured to be 62.30 and 94.7% in 20 wt % NaCl at 1 kW m^-2 irradiation, respectively. Furthermore, no obvious salt accumulation was observed after 30 d of continuous operation at real sunlight irradiation, implying an outstanding long-term stability for practical solar steam generation.

Multilayer graphite nano-sheet composite hydrogel for solar desalination systems with floatability and recyclability

The application of carbon-based nanomaterials with high photothermal conversion efficiencies in solar desalination has the advantages of economy, environmental protection, availability and sustainability.

Multifunctional Silica-Silicone Nanocomposite with Regenerative Superhydrophobic Capabilities

Superhydrophobic surfaces have been garnering increased interest because of their adaptive characteristics. However, concerns regarding their durability and complex fabrication techniques have limited their widespread adoption. In our study, we have developed an effective, durable, and versatile silica-silicone nanocomposite that can be applied through spray coating or bulk synthesized as superhydrophobic monoliths through a facile, economic, and scalable fabrication technique. For spray-coated samples, superhydrophobicity was achieved for concentrations above 9%. However, poor adhesion was observed for concentrations above 20%. Through extensive surface morphology studies, it was determined that a delicate balance between the polymer and dispersed superhydrophobic silica nanoparticles exists at a concentration of 14%. This concentration is necessary for developing the desired hierarchical structure and providing sufficient adhesion with the substrate. The monoliths were fabricated into complex geometries, with superhydrophobicity being observed in the 5 and 9% specimens. The hierarchical structure was formed through controlled surface abrasion, which created the microscale roughness and concurrently exposed the embedded silica nanoparticles. It was found that a monolith with a concentration of 9% provides excellent water repellency as well as a suitable emulsion viscosity to facilitate the molding process. Though compressive loading (up to 10 MPa) damages the monolith, the superhydrophobic performance can be quickly restored through abrasive layer removal. Both spray-coated and monolith specimens retained their superhydrophobicity after being subjected to high temperatures (up to 350 °C) and corrosive environments (pH 1-13) for 2 h.

Photothermal materials for efficient solar powered steam generation

Solar powered steam generation is an emerging area in the field of energy harvest and sustainable technologies. The nano-structured photothermal materials are able to harvest energy from the full solar spectrum and convert it to heat with high efficiency. Moreover, the materials and structures for heat management as well as the mass transportation are also brought to the forefront. Several groups have reported their materials and structures as solutions for high performance devices, a few creatively coupled other physical fields with solar energy to achieve even better results. This paper provides a systematic review on the recent developments in photothermal nanomaterial discovery, material selection, structural design and mass/heat management, as well as their applications in seawater desalination and fresh water production from waste water with free solar energy. It also discusses current technical challenges and likely future developments. This article will help to stimulate novel ideas and new designs for the photothermal materials, towards efficient, low cost practical solar-driven clean water production.

Pathways and challenges for efficient solar-thermal desalination

Solar-thermal desalination (STD) is a potentially low-cost, sustainable approach for providing high-quality fresh water in the absence of water and energy infrastructures. Despite recent efforts to advance STD by improving heat-absorbing materials and system designs, the best strategies for maximizing STD performance remain uncertain. To address this problem, we identify three major steps in distillation-based STD: (i) light-to-heat energy conversion, (ii) thermal vapor generation, and (iii) conversion of vapor to water via condensation. Using specific water productivity as a quantitative metric for energy efficiency, we show that efficient recovery of the latent heat of condensation is critical for STD performance enhancement, because solar vapor generation has already been pushed toward its performance limit. We also demonstrate that STD cannot compete with photovoltaic reverse osmosis desalination in energy efficiency. We conclude by emphasizing the importance of factors other than energy efficiency, including cost, ease of maintenance, and applicability to hypersaline waters.

A novel composite hydrogel for solar evaporation enhancement at air-water interface

This paper reports a facile approach to synthesize a novel composite hydrogel with graphene oxide (GO), silica aerogel (SA), acrylamide (AM), and poly(vinyl alcohol) (PVA) through physical and chemical cross-linking method. The composite hydrogel (GO/SA PAM-PVA hydrogel) exhibits excellent solar evaporation property, good water transmission capacity, and floatability. The GO nanosheets dispersed homogeneously in the hydrogel could provide prominent photothermal conversion efficiency to heat water for evaporation. Excellent hydrophilicity of hydrogel promotes the water molecules transport from the bottom to the top of the hydrogel, which can increase evaporation efficiency. The SA in the hydrogel makes the GO/SA PAM-PVA hydrogel floatable, which is crucial for improving evaporation efficiency because evaporation occurs primarily at several molecular layers on the surface of the water. Furthermore, the self-cleaning ability derived from SA of the GO/SA PAM-PVA hydrogel surface provides a convenient recycling and reusing process for practical applications. The evaporation mass of seawater achieved by the GO/SA PAM-PVA hydrogel is 6 times higher than that of traditional process at an optical density of 2 kW m^-2 for 30 min. Meanwhile, the evaporation efficiency of GO/SA PAM-PVA hydrogel remains good during reuse.

A High-Performance Self-Regenerating Solar Evaporator for Continuous Water Desalination

Emerging solar desalination by interfacial evaporation shows great potential in response to global water scarcity because of its high solar-to-vapor efficiency, low environmental impact, and off-grid capability. However, solute accumulation at the heating interface has severely impacted the performance and long-term stability of current solar evaporation systems. Here, a self-regenerating solar evaporator featuring excellent antifouling properties using a rationally designed artificial channel-array in a natural wood substrate is reported. Upon solar evaporation, salt concentration gradients are formed between the millimeter-sized drilled channels (with a low salt concentration) and the microsized natural wood channels (with a high salt concentration) due to their different hydraulic conductivities. The concentration gradients allow spontaneous interchannel salt exchange through the 1-2 µm pits, leading to the dilution of salt in the microsized wood channels. The drilled channels with high hydraulic conductivities thus function as salt-rejection pathways, which can rapidly exchange the salt with the bulk solution, enabling the real-time self-regeneration of the evaporator. Compared to other salt-rejection designs, the solar evaporator exhibits the highest efficiency (≈75%) in a highly concentrated salt solution (20 wt% NaCl) under 1 sun irradiation, as well as long-term stability (over 100 h of continuous operation).

Hollow black TiAlOx nanocomposites for solar thermal desalination

Although a solar-thermal conversion technique shows great potential for seawater desalination, there remains a grand challenge in exploring low-cost and high-efficiency photothermal materials. We report here a molten salt assisted galvanic replacement method for preparing a hollow black TiAlO_x composite, which features a high solar absorptivity with up to 90.2% and has a high efficiency of 71.1% in a high salinity solution containing 15.3 wt% NaCl (∼5 times more concentrated than seawater). We exemplify the practical application of such hollow black TiAlO_x composites as photothermal composites by setting up the automatic and manual tracking of solar desalination devices with a photic area of ∼1.0 m², which can produce purified water with a rate of above 4.0 L m^-2 day^-1 in high-salinity water under natural light irradiation, and maintains good stability upon 5 days of continuous running. The advantages of the as-developed hollow black TiAlO_x composites, including scalability, low cost, and high photothermal conversion efficiency, may open up a promising avenue practical application in seawater desalination.

A Moisture-Penetrating Humidity Pump Directly Powered by One-Sun Illumination

There is broad demand for humidity control for industrial, commercial, and residential applications. Current humidity pumping technologies require intensive maintenance because of the complexity of their mechanical structures. Furthermore, indirect utilization of solar energy increases both cost and energy loss. Here, we demonstrate a new humidity pumping concept based on multilayer moisture permeable panels. Such panels, with a simple structure, may allow the penetration of moisture from indoor (adsorption) to outdoor (desorption) with little heat loss. One-sun illumination is introduced as the direct energy source. A proof-of-concept prototype is designed and established, successfully dehumidifying indoor air with the best dehumidification rate of 33.8 g⋅m⁻²⋅h⁻¹. By applying such humidity pump, the indoor latent heat load can be handled independently, without any auxiliary unit, thus consuming no electricity.

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We propose a concept of moisture-permeable panel that enables moisture penetration

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A humidity pump prototype using the moisture-permeable panel is designed

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The humidity pump can reduce the indoor relative humidity to a medium level

The revival of thermal utilization from the Sun: interfacial solar vapor generation

Since solar energy is the ultimate energy resource and a significant amount of global energy utilization goes through heat, there have been persistent efforts for centuries to develop devices and systems for solar–thermal conversion. Most recently, interfacial solar vapor generation, as an emerging concept of solar–thermal conversion, has gained significant attention for its great potentials in various fields such as desalination, sterilization, catalysis, etc. With the advances of rationally designed materials and structures and photon and thermal management at the nanoscale, interfacial solar vapor generation has demonstrated both thermodynamic and kinetical advantages over conventional strategies. In this review, we aim to illustrate the definition, mechanism and figures of merit of interfacial solar vapor generation, and to summarize the development progress of relevant materials and applications, as well as to provide a prospective view of the future.

Facile and Scalable Fabrication of Surface-Modified Sponge for Efficient Solar Steam Generation

Solar steam generation is a highly promising technology for harvesting solar energy and desalination. Here, a new solar steam generation system is introduced based on a surface-modified polyurethane sponge with bilayered structures for efficient solar steam generation. The top layer, coated with polydimethylsiloxane-modified graphite powder, serves as light-to-heat conversion layer with a broad optical absorption, whereas the lower part of the sponge acts as a thermal insulator with a low thermal conductivity in the wet state (0.13882 W m^-1  K^-1 ). In addition, the strong hydrophobic wettability of the top layer (water contact angle: 148°) enables self-floating behavior on water, which is beneficial for practical applications. The results show that compared with a silver-nanoparticle-doped sponge and an acid-etched sponge doped with silver nanoparticles the graphite-modified sponge (GS) exhibits the highest evaporation efficiency of 73.3 % under 1 kW m² irradiation, which is 2.6 times that of pure water and far higher than that of untreated polyurethane sponge (36.0 %). The GS shows excellent stability, and its evaporation efficiency remains unchanged even after immersion in water for one month. Based on its cost-efficient, simple, and scalable manufacturing process, excellent mechanical stability, and high recyclability, the GS shows great potential as an efficient photothermal material for a wide range of large-scale applications such as solar steam generation, light absorption, heat localization, and seawater desalination.

Solar Photothermal Electrodes for Highly Efficient Microbial Energy Harvesting at Low Ambient Temperatures

Temperature is an important parameter for the performance of bioelectrochemical systems (BESs). Energy-intensive bulk water heating has been usually employed to maintain a desired temperature for the BESs. This study concerns a proof-of-concept of a light-to-heat photothermal electrode for solar heating of a local electroactive biofilm in a BES for efficient microbial energy harvesting at low temperatures as a replacement for bulk water heating approaches. The photothermal electrode was prepared by coating Ti₃ C₂ T_x MXene sunlight absorber onto carbon felt. The as-prepared photothermal electrode could efficiently raise the local temperature of the bioelectrode to approximately 30 °C from low bulk water temperatures (i.e., 10, 15, and 20 °C) under simulated sunlight illumination. As a result, highly efficient microbial energy could be harvested from the low-temperature BES equipped with a photothermal electrode without bulk water heating. This study represents a new avenue for the design and fabrication of electrodes for temperature-sensitive electrochemical and biological systems.

All-Poly(ionic liquid) Membrane-Derived Porous Carbon Membranes: Scalable Synthesis and Application for Photothermal Conversion in Seawater Desalination

Herein, we introduce a straightforward, scalable, and technologically relevant strategy to manufacture charged porous polymer membranes (CPMs) in a controllable manner. The pore sizes and porous architectures of CPMs are well-controlled by rational choice of anions in poly(ionic liquid)s (PILs). Continuously, heteroatom-doped hierarchically porous carbon membrane (HCMs) can be readily fabricated via morphology-maintaining carbonization of as-prepared CPMs. These HCMs, as photothermal membranes, exhibited excellent performance for solar seawater desalination, representing a promising strategy to construct advanced functional nanomaterials for portable water production technologies.

Copper Sulfide-Based Plasmonic Photothermal Membrane for High-Efficiency Solar Vapor Generation

Solar vapor generation has attracted tremendous attention as one of the most efficient ways of utilizing solar energy. It is highly desirable to develop low-cost, eco-friendly, and high-efficiency solar absorbers for practical applications of solar vapor generation. Herein, a three-dimensional plasmonic covellite CuS hierarchical nanostructure has been synthesized as the light-absorbing material via a facile one-pot hydrothermal method for structurally integrated solar absorbers with microporous poly(vinylidene fluoride) membrane (PVDFM) as the supporting material. A broadband and highly efficient light absorption has been achieved in the wavelength of 300-2500 nm, along with high water evaporation efficiencies of 90.4 ± 1.1 and 93.3 ± 2.0% under 1 and 4 sun irradiation, respectively. Meanwhile, stable performance has been demonstrated for over 20 consecutive runs without much performance degradation. To the best of our knowledge, this is the highest performance among the copper sulfide-based solar absorbers. With the additional features of low-cost and convenient fabrication, this plasmonic solar absorber exhibits a tremendous potential for practical solar vapor generation.

Melt Electrospun Reduced Tungsten Oxide /Polylactic Acid Fiber Membranes as a Photothermal Material for Light-Driven Interfacial Water Evaporation

The development of efficient photothermal materials is the most important issue in solar water evaporation. In this work, melt electrospun reduced tungsten oxide/polylactic acid (WO_2.72/PLA) fiber membranes were successfully prepared with improved near-infrared (NIR) photothermal conversion properties owing to strong NIR photoabsorption by the metal oxide. WO_2.72 powder nanoparticles were incorporated into PLA matrix by melt processing, following which the composites were extruded into wires using a single screw extruder. Subsequently, fiber membranes were prepared from the extruded wire of the WO_2.72/PLA composite by melt electrospinning, which is a cost-effective technique that can produce fiber membranes without the addition of environmentally unfriendly chemicals. The melt electrospun WO_2.72/PLA fiber membranes, floatable on water due to surface hydrophobicity, were systematically designed for, and applied to, vapor generation based on the interfacial concept of solar heating. With the photothermal WO_2.72/PLA fiber membrane containing 7 wt % WO_2.72 nanoparticles, the water evaporation efficiency was reached 81.39%, which is higher than that for the pure PLA fiber membrane and bulk water. Thus, this work contributes to the development of novel photothermal fiber membranes in order to enhance light-driven water evaporation performance for potential applications in the fields of water treatment and desalination.

Bio-inspired Edible Superhydrophobic Interface for Reducing Residual Liquid Food

Significant wastage of residual liquid food, such as milk, yogurt, and honey, in food containers has attracted great attention. In this work, a bio-inspired edible superhydrophobic interface was fabricated using U.S. Food and Drug Administration-approved and edible honeycomb wax, arabic gum, and gelatin by a simple and low-cost method. The bio-inspired edible superhydrophobic interface showed multiscale structures, which were similar to that of a lotus leaf surface. This bio-inspired edible superhydrophobic interface displayed high contact angles for a variety of liquid foods, and the residue of liquid foods could be effectively reduced using the bio-inspired interface. To improve the adhesive force of the superhydrophobic interface, a flexible edible elastic film was fabricated between the interface and substrate material. After repeated folding and flushing for a long time, the interface still maintained excellent superhydrophobic property. The bio-inspired edible superhydrophobic interface showed good biocompatibility, which may have potential applications as a functional packaging interface material.

Thermally Absorptive Blankets for Highly Efficient Snowbank Melting

Fallen snow is one of the most reflective surfaces found in nature. As a result, snowbanks can take many weeks to melt even when the air temperature is above freezing. Here, we introduce a simple and passive method for quickly melting snowbanks by draping a thermally absorptive blanket over the snow. Using controlled experimental conditions, it was observed that snowbanks can melt 300% faster when a thermally absorptive blanket is placed on top. The mechanism is the threefold increase in absorptivity of the spray-coated blanket compared to bare snow, which allows the vast majority of the irradiation to be used to overcome the latent heat of fusion.

Carbon-Based Sunlight Absorbers in Solar-Driven Steam Generation Devices

Carbon-based sunlight absorbers in solar-driven steam generation have recently attracted much attention due to the possibility of huge applications of low-cost steam for medical sterilization or sanitization, seawater desalination, chemical distillation, and water purification. In this minireview, recent developments in carbon-based sunlight absorbers in solar-driven steam generation systems are reviewed, including graphene, graphite, carbon nanotubes, other carbon materials, and carbon-based composite materials, highlighting important contributions worldwide that promise low-cost, efficient, robust, reusable, chemically stable, and excellent broadband solar absorption. Furthermore, the crucial challenges associated with employing carbon materials in this field are emphasized.

Layered tin monoselenide as advanced photothermal conversion materials for efficient solar energy-driven water evaporation

Solar energy-driven water evaporation lays a solid foundation for important photothermal applications such as sterilization, seawater desalination, and electricity generation. Due to the strong light-matter coupling, broad absorption wavelength range, and prominent quantum confinement effect, layered tin monoselenide (SnSe) holds a great potential to effectively harness solar irradiation and convert it to heat energy. In this study, SnSe is successfully deposited on a centimeter-scale nickel foam using a facile one-step pulsed-laser deposition approach. Importantly, the maximum evaporation rate of SnSe-coated nickel foam (SnSe@NF) reaches 0.85 kg m^-2 h^-1, which is even 21% larger than that obtained with the commercial super blue coating (0.7 kg m^-2 h^-1) under the same condition. A systematic analysis reveals that its good photothermal conversion capability is attributed to the synergetic effect of multi-scattering-induced light trapping and the optimal trade-off between light absorption and phonon emission. Finally, the SnSe@NF device is further used for seawater evaporation, demonstrating a comparable evaporation rate (0.8 kg m^-2 h^-1) to that of fresh water and good stability over many cycles of usage. In summary, the current contribution depicts a facile one-step scenario for the economical and efficient solar-enabled SnSe@NF evaporation devices. More importantly, an in-depth analysis of the photothermal conversion mechanism underneath the layered materials depicts a fundamental paradigm for the design and application of photothermal devices based on them in the future.

A durable monolithic polymer foam for efficient solar steam generation

Efficient and cost-effective solar steam generation requires self-floating evaporators which can convert light into heat, prevent unnecessary heat loss and greatly accelerate evaporation without solar concentrators. Currently, the most efficient evaporators (efficiency of ∼80% under 1 sun) are invariably built from inorganic materials, which are difficult to mold into monolithic sheets. Here, we present a new polymer which can be easily solution processed into a self-floating monolithic foam. The single-component foam can be used as an evaporator with an efficiency at 1 sun comparable to that of the best graphene-based evaporators. Even at 0.5 sun, the efficiency can reach 80%. Moreover, the foam is mechanically strong, thermally stable to 300 °C and chemically resistant to organic solvents.

Synthetic Graphene Oxide Leaf for Solar Desalination with Zero Liquid Discharge

Water vapor generation through sunlight harvesting and heat localization by carbon-based porous thin film materials holds great promise for sustainable, energy-efficient desalination and water treatment. However, the applicability of such materials in a high-salinity environment emphasizing zero-liquid-discharge brine disposal has not been studied. This paper reports the characterization and evaporation performance of a nature-inspired synthetic leaf made of graphene oxide (GO) thin film material, which exhibited broadband light absorption and excellent stability in high-salinity water. Under 0.82-sun illumination (825 W/m²), a GO leaf floating on water generated steam at a rate of 1.1 L per m² per hour (LMH) with a light-to-vapor energy conversion efficiency of 54%, while a GO leaf lifted above water in a tree-like configuration generated steam at a rate of 2.0 LMH with an energy efficiency of 78%. The evaporation rate increased with increasing light intensity and decreased with increasing salinity. During a long-term evaporation experiment with a 15 wt % NaCl solution, the GO leaf demonstrated stable performance despite gradual and eventually severe accumulation of salt crystals on the leaf surface. Furthermore, the GO leaf can be easily restored to its pristine condition by simply scraping off salt crystals from its surface and rinsing with water. Therefore, the robust high performance and relatively low fabrication cost of the synthetic GO leaf could potentially unlock a new generation of desalination technology that can be entirely solar-powered and achieve zero liquid discharge.

Facile Fabrication and Characterization of a PDMS-Derived Candle Soot Coated Stable Biocompatible Superhydrophobic and Superhemophobic Surface

We report a simple, inexpensive, rapid, and one-step method for the fabrication of a stable and biocompatible superhydrophobic and superhemophobic surface. The proposed surface comprises candle soot particles embedded in a mixture of PDMS+n-hexane serving as the base material. The mechanism responsible for the superhydrophobic behavior of the surface is explained, and the surface is characterized based on its morphology and elemental composition, wetting properties, mechanical and chemical stability, and biocompatibility. The effect of %n-hexane in PDMS, the thickness of the PDMS+n-hexane layer (in terms of spin coating speed) and sooting time on the wetting property of the surface is studied. The proposed surface exhibits nanoscale surface asperities (average roughness of 187 nm), chemical compositions of soot particles, very high water and blood repellency along with excellent mechanical and chemical stability and excellent biocompatibility against blood sample and biological cells. The water contact angle and roll-off angle is measured as 160° ± 1° and 2°, respectively, and the blood contact angle is found to be 154° ± 1°, which indicates that the surface is superhydrophobic and superhemophobic. The proposed superhydrophobic and superhemophobic surface offers significantly improved (>40%) cell viability as compared to glass and PDMS surfaces.

3D-Printed, All-in-One Evaporator for High-Efficiency Solar Steam Generation under 1 Sun Illumination

Using solar energy to generate steam is a clean and sustainable approach to addressing the issue of water shortage. The current challenge for solar steam generation is to develop easy-to-manufacture and scalable methods which can convert solar irradiation into exploitable thermal energy with high efficiency. Although various material and structure designs have been reported, high efficiency in solar steam generation usually can be achieved only at concentrated solar illumination. For the first time, 3D printing to construct an all-in-one evaporator with a concave structure for high-efficiency solar steam generation under 1 sun illumination is used. The solar-steam-generation device has a high porosity (97.3%) and efficient broadband solar absorption (>97%). The 3D-printed porous evaporator with intrinsic low thermal conductivity enables heat localization and effectively alleviates thermal dissipation to the bulk water. As a result, the 3D-printed evaporator has a high solar steam efficiency of 85.6% under 1 sun illumination (1 kW m^-2 ), which is among the best compared with other reported evaporators. The all-in-one structure design using the advanced 3D printing fabrication technique offers a new approach to solar energy harvesting for high-efficiency steam generation.

Wood-Graphene Oxide Composite for Highly Efficient Solar Steam Generation and Desalination

Solar steam generation is a highly promising technology for harvesting solar energy, desalination and water purification. We introduce a novel bilayered structure composed of wood and graphene oxide (GO) for highly efficient solar steam generation. The GO layer deposited on the microporous wood provides broad optical absorption and high photothermal conversion resulting in rapid increase in the temperature at the liquid surface. On the other hand, wood serves as a thermal insulator to confine the photothermal heat to the evaporative surface and to facilitate the efficient transport of water from the bulk to the photothermally active space. Owing to the tailored bilayer structure and the optimal thermo-optical properties of the individual components, the wood-GO composite structure exhibited a solar thermal efficiency of ∼83% under simulated solar excitation at a power density of 12 kW/m². The novel composite structure demonstrated here is highly scalable and cost-efficient, making it an attractive material for various applications involving large light absorption, photothermal conversion and heat localization.

Wettability of monolayer graphene/single-walled carbon nanotube hybrid films

This work presents a method for fabricating monolayer graphene/single-walled carbon nanotube hybrid films. We found that the wettability of monolayer graphene has a half-transparent behaviour.

Magnetically recyclable self-assembled thin films for highly efficient water evaporation by interfacial solar heating

Hydrophobic magnetic microspheres can self-assemble into a thin film and float on the surface of water. The formed film was used as a photothermal material for water evaporation based on a new concept of interfacial solar heating.

Constructing Black Titania with Unique Nanocage Structure for Solar Desalination

Solar desalination driven by solar radiation as heat source is freely available, however, hindered by low efficiency. Herein, we first design and synthesize black titania with a unique nanocage structure simultaneously with light trapping effect to enhance light harvesting, well-crystallized interconnected nanograins to accelerate the heat transfer from titania to water and with opening mesopores (4-10 nm) to facilitate the permeation of water vapor. Furthermore, the coated self-floating black titania nanocages film localizes the temperature increase at the water-air interface rather than uniformly heating the bulk of the water, which ultimately results in a solar-thermal conversion efficiency as high as 70.9% under a simulated solar light with an intensity of 1 kW m^-2 (1 sun). This finding should inspire new black materials with rationally designed structure for superior solar desalination performance.

Bilayered Biofoam for Highly Efficient Solar Steam Generation

A novel bilayered hybrid biofoam composed of a bacterial nanocellulose (BNC) layer and a reduced graphene oxide (RGO)-filled BNC layer is introduced for highly efficient solar steam generation. The biofoam exhibits a solar thermal efficiency of ≈83% under simulated solar illumination (10 kW m^-2 ). The fabrication method introduced here is highly scalable and cost-efficient.

Water-Repellent Properties of Superhydrophobic and Lubricant-Infused "Slippery" Surfaces: A Brief Study on the Functions and Applications

Bioinspired water-repellent materials offer a wealth of opportunities to solve scientific and technological issues. Lotus-leaf and pitcher plants represent two types of antiwetting surfaces, i.e., superhydrophobic and lubricant-infused "slippery" surfaces. Here we investigate the functions and applications of those two types of interfacial materials. The superhydrophobic surface was fabricated on the basis of a hydrophobic fumed silica nanoparticle/poly(dimethylsiloxane) composite layer, and the lubricant-infused "slippery" surface was prepared on the basis of silicone oil infusion. The fabrication, characteristics, and functions of both substrates were studied, including the wettability, transparency, adhesive force, dynamic droplet impact, antifogging, self-cleaning ability, etc. The advantages and disadvantages of the surfaces were briefly discussed, indicating the most suitable applications of the antiwetting materials. This contribution is aimed at providing meaningful information on how to select water-repellent substrates to solve the scientific and practical issues, which can also stimulate new thinking for the development of antiwetting interfacial materials.

Development of a superhydrophobic polybenzoxazine surface with self-cleaning and reversible water adhesion properties

A superhydrophobic polybenzoxazine surface with self-cleaning properties is obtained, and is resistant to solvents and corrosive liquids.

Wettability and permeation of ethanol/water mixture on porous mesh surface

A serial of copper meshes with different chemical composition and roughness was prepared by modifying different mixed thiols, which showed different wetting behavior and permeation behavior for different ethanol/water mixed solution.