Solar-driven Interfacial Evaporation Research Articles

A self-sufficient catalytic nanofiber evaporator for solar-driven efficient water purification through in-situ hydrogen peroxide generation

Solar-driven interfacial water evaporation (SDIWE) is an emerging technology for the production of clean water driven by inexhaustible energy source, but its application suffers from volatile organic compounds (VOCs) escaping into condensate water. Herein, a bifunctional SDIWE system integrated with Fenton process was proposed to achieve self-sufficient (not adding any additional chemicals to feed water) high-quality freshwater production from VOCs-contained wastewater through in-situ hydrogen peroxide (H2O2) generation. The hybrid SDIWE system based on AgNPs (Ag nanoparticles)@graphitic carbon nitride (g-C3N4)/beta-iron hydroxide oxide (β-FeOOH)-Polyacrylonitrile (AgG/Fe-PAN) nanofiber membrane exhibited an excellent evaporation performance (1.61 kg m-2h−1) under one sun (1 kW m−2). Significantly, in the absence of external oxidant source, the phenol removal rate in condensate water reached 98.4 ± 0.2 % due to the synergic photocatalysis technology and Fenton reaction, which was 6.1 times that of sole SDIWE (16.2 ± 0.5 %). Mechanism analysis reveals that H2O2 was effectively in-situ generated by AgNPs@g-C3N4 particles (∼18.8 μM at 4 h). Subsequently, the produced H2O2 was further activated to •OH radicals via β-FeOOH that ensures the VOCs decomposition during rapid steam generation. Meanwhile, the hybrid system not only exhibited an excellent phenol removal rate of 91.6 ± 0.6 % in wide pH ranges (1–11), but also ensured a good removal performance for various organic pollutants and excellent antibacterial properties. To sum up, the hybrid system has successfully integrated SDIWE technology with various advanced oxidation processes (AOPs), providing a novel way for the pollution-free production of high-quality clean water during the SDIWE process for water purification.

Advanced solar-driven hydrogel sponge for efficient heavy metal wastewater purification and clean water production through interfacial evaporation

Solar-driven interfacial evaporation (SDIE) technology represents a promising solution for freshwater harvesting, characterized by its cost-effectiveness, eco-friendliness, and sustainability. Nevertheless, achieving efficient removal of heavy metal ions during the SDIE process remains a significant challenge. In this study, we present a cost-effective method to construct a hybrid hydrogel evaporator by incorporating the konjac glucomannan (KGM) and reduced graphene oxide (rGO) into a polyvinyl alcohol (PVA) network. The hybrid hydrogel evaporator features a three dimensional layered structure, full spectrum absorption capability, high stability and inherent salt diffusion ability. These characteristics enabling an evaporation rate of 1.61 kg m−2 h−1 from wastewater across varying pH values (2–12) and high salinity levels (1 kW m−2). Significantly, the hybrid polymer network within the hydrogel is rich in -OH groups, enabling concurrent wipe off heavy metal ions and organic dyes from wastewater. The results in a ten thousand times reduction in the concentration of heavy metals such as Cr3+, Mn2+, Cu2+, Zn2+, and Pb2+ in the wastewater. This study provides new insights into solar evaporation technology and contributes to addressing challenges related to water scarcity.

Highly efficient and robust oxygen vacancy-rich molybdenum trioxide aerogel evaporator for Photothermal conversion and clean water generation

Interfacial evaporation of seawater and other wastewater is used to produce clean water by the infinite solar energy which attracts an intense interest and displays a great prospect. An efficient and robust photothermal evaporator is a key to solar-driven interfacial evaporation. Herein, the oxygen vacancy-rich MoO3 aerogel evaporator is designed to purify seawater and wastewater. Hydrogen etching is used to construct oxygen vacancies of MoO3, which regulate its optical and thermophysical properties. MoO3* possesses stronger broadband absorption and lower reflectance than MoO3 across the wavelength ranges of 200 nm–2500 nm, which insures more energy input. Besides, band gap energy of MoO3* decreases from 2.90 eV of MoO3 to 1.92 eV, which is more beneficial for the visible light absorption and its degradation of organic pollutant. As a result, the MoO3*-based evaporator displays a higher evaporation rate of 1.78 kg m−2 h−1 as well as 92.6 % of efficiency for pure water at 1 sun illumination, in contrast to the MoO3-based evaporator with an evaporation rate of 1.04 kg m−2 h−1 and 60.0 % efficiency, suggesting that oxygen vacancies induced by hydrogen etching improve photothermal conversion efficiency. In practical application, the MoO3*-based evaporator also displays an excellent purification performance for seawater, heavy metal wastewater and tetracycline wastewater, in which the evaporation rates are close to pure water, and the quality of the purified water is better than drinking water specified by WHO standard. In addition, the defected MoO3*-based aerogel evaporator not only possesses an excellent thermal management, but also offers an excellent salt self-cleaning ability. This work convincingly demonstrates that the “defect chemistry” is perfect for constructing the defected MoO3* aerogel evaporator for sustainable production of clean water from seawater, heavy metal wastewater and tetracycline wastewater by means of the solar-driven interfacial evaporation.

Gradient hydrophobic evaporator based on ODT modified Co3O4/NF enables efficient desalination and thermoelectric power generation

The utilization of solar-driven interfacial evaporation technology for desalination and power generation is a promising strategy for dealing with the water and energy shortage crisis, but the balance between high photo-thermal conversion and minimizing heat loss is the major challenge that hinder its widespread application.. In this work, we innovatively design a surface-to-bottom gradient hydrophobic evaporator. Within array structured Co3O4 nanoparticles grown on nickel foam (Co3O4/NF), the trapping light system can realize superior photo-thermal conversion efficiency. Applying ortho-octadecanethiol (ODT) to the surface of Co3O4/NF to construct the gradient hydrophobic structure can optimize the water content within the inner pores, thereby minimizing heat loss. Under 1 sun illumination, the evaporation device realizes a prominent evaporation rate of 1.76 kg m-2h−1, which is 11.4 % higher than that of hydrophilic counterparts (1.55 kg m-2h−1). In addition, the gradient hydrophobic evaporator operates stably in 3.5 wt% NaCl for more than 8 h without salt crystallization. Furthermore, it achieves a sunlight-enhanced voltage of about 97.8 mV and an open-circuit current of 14.6 mA. Our research introduces an innovative solar-powered water treatment technology that effectively addresses the dual challenges of desalination and electricity generation, paving the way for sustainable development.

Surface patterned polyvinyl alcohol/CNT hydrogels for sustained solar powered high concentration brine desalination and salt harvesting

Solar-driven interfacial evaporation is an attractive way to achieve water purification. However, high water evaporation rates often result in the precipitation of salt crystals on the surface of the evaporator leading to decay of the evaporation efficiency over time, which makes it difficult to balance high water evaporation rates with salt resistance. Herein, an anisotropic polyvinyl alcohol/CNT hydrogel is constructed by directional freezing and surface patterning. The polymer backbone formed by the polyvinyl alcohol chains interacts with the water clusters to reduce the evaporation enthalpy of water and the absorbed water can be released by squeezing the hydrogels due to the micron-sized vertically aligned pores. More importantly, by designing the structure of the hydrogels surface, the gas–liquid interface of the evaporators can be increased while the growth direction of the salt crystals can be controlled. As a result, the water evaporation rate can be increased from 3.26 kg m-2h−1 to 3.69 kg m-2h−1 under one sun irradiation through surface patterning. After 50 h of continuous operation in 10 wt% NaCl solution under one sun irradiation, the water evaporation rate gradually increases and a large amount of salt collection is collected, which proves its satisfactory salt resistance.

Simultaneous realization of efficient solar evaporation and electricity collection through dual regulation of chemical composition and pore channels

The solar-driven interfacial evaporation is a recently developed zero-energy technology for seawater desalination. However, the low evaporation rate poses a significant obstacle to its industrial application, and the collection of streaming potential formed during the evaporation process remains challenging. In this paper, we constructed a solar evaporator capable of simultaneously achieving efficient solar evaporation and electricity collection. Specifically, a double network structure hydrogel comprising polyvinyl alcohol (PVA) and TEMPO-oxidized cellulose nanoparticles nanofibers (TOCNFs) was fabricated using ice templating, with the addition of sodium lignosulfonate (SLS) to further modulate water distribution within the network. The incorporation of carbon nanotubes (CNTs) enabled the achievement of a PVA/TOCNFs/SLS (PTFS) gel-based solar evaporator. The strong electronegativity carried by the TOCNFs enhances the electrostatic repulsion in the PVA-TOCNFs network, thus improving the mechanical properties of PTFS evaporator. The introduction of SLS, which contains abundant sulfonate groups, provides certain antibacterial properties to PTFS evaporator. Due to the presence of numerous hydrophilic groups, both TOCNFs and SLS can form weak hydrogen bonds with water. Through the synergistic effect of TOCNFs and SLS, the latent heat of water in PTFS evaporator is reduced to 924 kJ kg−1, enabling an evaporation rate of 3.70 kg m−2h−1 under 1 sun irradiation. Owing to the smaller pore size relative to the Debye radius and the presence of electronegative functional groups within the pores of PTFS evaporators, an overlapping bilayer is formed when water flows through, resulting in an open-circuit voltage increase of up to 270 mV. The integration of high-efficiency solar evaporation with streaming potential collection presents a novel avenue for enhancing the utilization of solar energy.

Bidirectional solar water production enabled by a breathable Janus photothermal material

Solar-driven interfacial water evaporation offers a promising solution to the global scarcity of freshwater. Despite advances in increasing evaporation rates, current condensate productivity is limited to 0.3 − 0.5 kg m−2 h−1 due to unidirectional vapor diffusion, which is insufficient to satisfy water demands. This paper introduces a bidirectional solar water production (BSWP) device that utilizes a breathable Janus photothermal material made from recycled cotton fabric. The BSWP device allows vapor to diffuse in both upward and downward directions of the evaporation interface. This design features dual condensers, addressing the limitations of traditional solar stills by reducing vapor concentration and minimizing light loss due to condensation on the top cover receiving light. Under 1 sun illumination, the BSWP device achieves a water yield of 1.06 kg m−2 h−1 with a solar-to-water efficiency of 71%. An 10-hour outdoor experiment demonstrates that the BSWP device can yield a water flux of 9.65 kg m−2, showcasing its potential for efficient water generation in practical environmental conditions. The present work provides a new perspective on the structural design of direct solar desalination configurations, potentially offering a more effective solution to cope with global water scarcity.

Hydrothermally synthesized cobalt oxide/polydimethylsiloxane based photothermal absorber for superior thermal energy conversion and water evaporation application

Solar-driven interfacial evaporation has garnered worldwide interest in recent years due to its unique vapor generating capacity using sustainable solar energy. Many photoabsorber have been studied for conversion of photothermal energy and heat absorption. Unfortunately, the majority of the absorber materials in supply are pricey, and the installation procedures tend to be intricate. This research focuses on the ongoing difficulty of creating cost-efficient photothermal materials that have excellent light absorption and simple manufacturing processes. We created a novel composites coated with Cobalt oxide and polydimethylsiloxane (Co3O4/PDMS) which successfully produce energy and purify water utilizing an extensive spectrum of solar energy. Hydrothermally synthesized Co3O4 particles exhibit distinct optical properties in the UV–Vis region due to ligand field transitions and charge transfer between Co2⁺ and Co³⁺ ions. Additionally, these particles exhibits a strong absorption in the NIR region due to the intervalence charge transfer and d-d transitions, enhancing their photothermal activity. This culminates in outstanding light-to-heat transformation in the Co3O4/PDMS composite, which maintains a surface temperature of 42.7 °C compared to 33.7 °C for pristine PDMS under standard 1 sun intensity for 5 min. The flexible Co3O4/PDMS composite transfers solar energy to electric energy, producing ∼99 mV with 1 sun irradiation, while bare PDMS only achieved a voltage of 61 mV under 1 sun circumstances. An efficient double layer Co3O4/PDMS@MF sponge achieved an evaporation rate of 1.33 kg m−2 h−1 with the photothermal conversion efficiency of 68.8 %. These results motivate thorough investigation in photothermal potential of Co3O4, revealing the promising possibilities for harnessing solar-thermal energy and presents a novel method for using solar power to purify water and generate electricity.

Bioinspired Photothermal Metal-Organic Framework Cocrystal with Ultra-Fast Water Transporting Channels for Solar-Driven Interfacial Water Evaporation.

Herein, a bioinspired metal-organic framework (MOF) cocrystal produced from the co-assembly of a MOF [Ni3(hexaiminobenzene)2, Ni3(HIB)2] and p-chloranils (CHLs) is reported. Because of the 2D conjugation nature and the formation of persistent anion radicals, this cocrystal shows an excellent photothermal property, and is further used as an absorber in solar-driven interfacial water evaporation. The solar-driven interfacial water evaporation rate (4.04 kg m-2 h-1) is among the best compared with those of previously reported photothermal materials. Molecular dynamics simulation results suggested that the rotating of the CHL molecules relative to the MOF planes tuned the pore size to enable the ultra-fast water transporting, and thus ultra-high water transporting rates (1.11 × 1011 and 3.21 × 1011 H2O s-1 channel-1 at 298.2 and 323.0 K, respectively) for layered cocrystal structures, that are much higher than that of aquaporins (≈1.1 × 1010 H2O s-1 channel-1 at 298.2 K), are observed. The superior solar-driven water evaporation performance is thus attributed to the synergistic effect of the ultra-fast water transporting pores together with the excellent photothermal property of the cocrystal. This research provided a biomimetic strategy of rational design and production of charge transfer cocrystals to modulate their pores and photothermal properties for solar-driven interfacial water evaporation.

Enhancing the sustainability of interfacial evaporation to mitigate solar intermittency via phase change thermal storage

Solar-driven interfacial water evaporation is a low-carbon footprint strategy for addressing global water scarcity. However, the operation of the evaporator requires continuity of solar radiation. Herein, the key to overcoming the intermittency of sunlight lies in utilizing the heat storage/release cycle of phase change materials. Additionally, the synergistic effect of high thermal conductivity materials and increased heat transfer area addresses the nonuniform spatial temperature within the heat storage device caused by the low thermal conductivity of molten paraffin. Although the heat transferred to the paraffin reduces the evaporation rate under illumination, the thermal storage/release capacity of paraffin increases the evaporation mass by 171.5% in darkness. Ultimately, after one light–dark cycle, the total evaporation mass over the entire period increased by 11.5%. Finally, although paraffin undergoes sensible and latent heat absorption and release across various temperature ranges during multiple light–dark cycles and prolonged operation, the phase change delays at different internal locations still ensure stable dark-state evaporation compensation for the evaporator, thereby enhancing the sustainability of the evaporation process.

Silk-based polyelectrolyte evaporator with excellent salt resistance for high-rate and stable solar desalination

Solar-driven interfacial evaporation technology is a promising solution to solve global freshwater shortages through desalination. However, salt accumulation in the evaporator affects light absorption and reduces evaporation efficiency, thereby significantly reducing the service life and operating efficiency of the evaporator. Herein, we propose a strategy for sustainable salt resistance that enables strong salt resistance and rapid water delivery by in situ polymerization of sodium acrylate (PAAS) on the directional channel. As a result, the as-prepared SF/rGO@PAAS can achieve a high evaporation rate of up to 2.31 kg m−2 h−1 and high evaporation efficiency of up to 98% under one sun, benefiting from the inherent hydrophilicity of silk fibroin (SF), the directional channel design of water transport layer, and the efficient solar light absorption in full spectrum of reduced graphene oxide (rGO). More importantly, due to the electrostatic effect of PAAS, the evaporator showed excellent salt resistance, with no salt precipitation for 5 days of continuous evaporation in simulated seawater (3.5 wt%) while maintaining the high evaporation rate. This salt resistant evaporator provides an effective solution to the salt accumulation and addresses a key challenge in sustainable desalination.

Low cost Non freeze-drying construction strategy of cellulose aerogels for efficient solar desalination

Aerogel-like materials with three-dimensional pore structures show great potential in the field of efficient solar-driven interfacial evaporation by virtue of their fast water transport as well as efficient energy confinement properties. However, the preparation of aerogels is currently limited by high-cost strategies such as freeze drying or supercritical drying. Here, we present a foam template-assisted (FTA) strategy for atmospheric pressure drying of cellulose nanofiber (CNF) aerogels. Building a robust CNF network is the key to resisting surface tension during water evaporation and achieving drying in ambient environments, which is achieved through cleverly designed ionic cross-linking with the help of FTA. Cellulose aerogel (CA) constructed using the FTA strategy exhibit lightweight (9 mg cm−3) and porous properties (porosity: > 99 %). The tannic-coated CA (TCA) was achieved by further polymerizing tannic acid on the CA surface, which has excellent photothermal conversion capability. Meanwhile, TCA achieved an impressive evaporation rate of 3.58 kg m-2h−1 and an energy efficiency of 97.2 % at 1sun radiation by virtue of its excellent energy confinement and water management capabilities. This strategy provides a promising solution for the low-cost construction of aerogels as well as for the realization of efficient solar-driven interfacial evaporators.

Three birds with one stone: Constructing Janus multilayer carbon fabric to boost solar-driven interfacial evaporation, electrical power generation and inhibit VOCs volatilization

Solar-driven interfacial evaporation technology has great potential to address both the freshwater and energy crises in a low-cost, environmentally friendly, and sustainable method. How to achieve highly efficient freshwater and energy harvesting simultaneously is still challenging. Here, a Janus-structured multilayer carbon fabric (JMCF) solar evaporator is proposed to effectively overcome the bottleneck in the cogeneration of fresh water and electricity. The Janus structure of the multilayer fabric effectively controls water supply upwards, improves light absorption and photothermal conversion, increases evaporation surface area, facilitates water vapor escape and inhibits VOCs volatilization. Accordingly, the optimized JMCF solar evaporator can achieve a high evaporation rate of 3.12 kg m-2h−1 and an output voltage of 0.577 V in 3.5 wt% seawater under 1 sun irradiation. In addition, the JMCF evaporation system also demonstrates good working stability, self-cleaning capacity, environmental adaptability, and economic feasibility. This work provides new ideas and inspiration for the design of high efficiency solar-driven interfacial evaporation system to address the freshwater scarcity, energy crisis, global change problem, etc.

Carbon Ink Enhanced Calcium Alginate-Based Hydrogel with Response Surface Methodology Optimized for Solar-Driven Salt-Tolerant Desalination.

The global shortage of freshwater resources is becoming more and more serious; therefore, it is necessary to obtain freshwater by desalinating seawater resources. Solar-driven interfacial photothermal evaporation, which is an environmentally friendly and energy-efficient technology, has been used to desalinate seawater for water purification and production. Herein, the IPCA hydrogel with abundant pores consisting of carbon ink as a photothermal conversion material and PU sponge loaded with calcium alginate as a water transport medium was successfully prepared and used to obtain portable water. The parameters of the synthesized IPCA are optimized by Response Surface Methodology analysis, and it was found that the IPCA exhibits a high evaporation efficiency of 3.779 kg m-2 h-1 and up to 95.98% of photothermal conversion capacity under one solar intensity. It maintains a high evaporation efficiency and salt resistance after 10 cycles of evaporation in actual seawater. Moreover, IPCA shows a high removal of various organic dye pollutants in wastewater. The results suggest a new approach for the preparation of simple, efficient, and green solar evaporators in practical application.

In Situ Growth of Well-Aligned MOF Nanoneedle Arrays into Composite Photothermal Membranes for Solar Desalination.

The solar-driven interfacial evaporation (SDIE) technology serves as a clean and facile approach combining seawater desalination to address water shortage and energy crisis. Recently, porous organic framework materials have aroused great attention, and the development of MOF-based composites with significant performance in photothermal conversion and water activation has become one of the important focuses in this field. In this work, an MOF-based composite photothermal membrane (PON@MOF) was prepared via the in situ growth of metal-organic framework (MOF) nanoneedle arrays induced by a pyridine-based organic polymer nanowire network (PON). The PON@MOF membrane possessed an MOF array layer, a PON-induced layer, and a porous support layer. The PON is rich in coordinated nitrogen atoms for anchoring the metal-ion source, and the main role of the PON layer is to provide favorable nucleation sites and orient in situ growth of well-aligned MOF nanoneedle arrays. With the highly conjugated framework of PON@MOF and the light trapping of the nanoarrays strengthening the photothermal conversion as well as the hydrophilic chemical structure facilitating the decrease of the water evaporation enthalpy, the PON@MOF membrane realizes highly efficient thermal vapor conversion. Under solar irradiation (1.0 kW m-2), PON@MOF demonstrated an evaporation rate of 2.14 kg m-2 h-1 and a solar-to-vapor conversion efficiency of 98.5%. Meanwhile, the PON@MOF membrane has excellent salt resistance and stability, highlighting its potential application in desalination. Overall, this work provides a special idea for the structural design of photothermal composites for solar desalination and freshwater production.

Eco-friendly and easy-to-prepare three-dimensional network constructed by tannic acid/polypyrrole/sodium alginate via triple action mechanism of Fe3+ for highly-efficient solar evaporation

Solar-driven interfacial evaporation (SIE) represents a promising desalination technology leveraging solar energy and seawater. Nevertheless, the majority of SIE systems face constraints such as high costs, intricate fabrication processes, and limited tolerance to salt. Therein, we designed and developed an eco-friendly, simple, and low-cost way to construct independent and elastic three-dimensional networks using tannic acid (TA), polypyrrole (PPy), and sodium alginate (SA) via the triple action mechanism of Fe3+ for efficient water evaporation (TPS-x). When the mass ratios of PPy and TA are designed as 1:2, 1:1, 2:1, and 3:1, and crosslinked with sodium alginate and FeCl3, four composites (TPS-1, TPS-2, TPS-3, and TPS-4) are obtained, in which the light absorption and evaporation properties of TPS-3 are the optimal, with an evaporation rate up to 2.451 kg m−2 h−1 and a photothermal conversion efficiency up to 84.74 %. Additionally, the TPS-3 evaporator has excellent stability and salt tolerance, maintaining more than 95.5 % of its original evaporation rate after 20 days of cycling tests. Due to its exceptional photothermal evaporation performance, TPS-3 shows potential for practical commercial applications, particularly in the fields of wastewater treatment and desalination.

Green conversion of waste polyester into few-layer graphene for interfacial solar-driven evaporation and hydroelectric electricity generation

The coupling of solar-driven interfacial evaporation with hydrovoltaic technology is emerged as a hopeful approach to alleviate energy crisis and freshwater shortage. However, constructing low-cost evaporators with high-performance freshwater and electricity co-generation and unveiling the co-generation mechanism remain a grand challenge. Herein, we report the green transformation of waste poly(ε-caprolactone) into graphene through a salt-assisted carbonization strategy and build a flexible bi-functional graphene-based evaporator for freshwater and electricity co-generation. The graphene exhibits a typical wrinkled structure with curved edges and is composed of 7–8 discontinuous layers with rich oxygen-containing groups. The graphene-based evaporator exhibits excellent sunlight absorption (98%), photo-to-thermal conversion property, good water transport ability, low water evaporation enthalpy, and low thermal conductivity of 0.06 W m−1 K−1. The evaporator not only exhibits a notable water evaporation rate (2.92 kg m−2 h−1), but also achieves the maximum output voltage of 310 mV, surpassing many previously reported evaporators/generators. The result of molecular dynamics simulation proves the diffusion difference between H+ and OH− in water and graphene, which eventually leads to the voltage generation. Not only will this work help to improve the upcycling of waste plastics and achieve carbon neutrality, but it will also open an avenue for co-generation of freshwater and electricity.

Bifunctional Photothermal Evaporator Based on an MXene/Fe-MOF Collaborative Effect toward Efficient Solar Steam Generation and Simultaneous VOC Removal.

Solar-driven interfacial water evaporation has become one of the most promising approaches to effectively harvesting freshwater, yet the fabrication of high-performance and multifunctional solar interfacial evaporators (SIEs) still remains a huge challenge to date. In this study, a multifunctional MXene and Fe-MOF@cellulose acetate/polyvinylpyrrolidone (MXM@CP) SIE was prepared via a facile "electrospinning and suction filtration deposition" coupling strategy. Thanks to the incorporation of MXene, MXM@CP displayed excellent photothermal conversion performance. Together with the fast water transport channel provided by the porous cellulose acetate electrospinning substrate, a remarkable solar-driven water evaporation property was achieved for MXM@CP, showing a higher water evaporation rate of 1.1 kg m-2 h-1 under one sun irradiation. Moreover, the resultant composite film also exhibited excellent Fenton catalytic activity to effectively degrade volatile organic compounds (VOCs) due to the synergistic effect of the MXene and Fe-based MOF (Fe-MOF). Particularly, a relatively higher degradation rate of 82.8% was acquired for the resulting evaporator toward the benzene contaminant. These results provide new insights into the construction of high-performance and multifunctional SIEs toward clean freshwater collection from the VOC-contaminated water system.

Tough, antimicrobial, recyclable hydrogel with tree-trunk-inspired core‐sheath structure for efficient all-day desalination

Solar-driven interfacial evaporation, an economically friendly freshwater harvesting technology, faces the challenge of achieving efficient all-day desalination. Inspired by the core‐sheath structure of tree trunks, herein, a hydrogel evaporator features internal vertical lamellar sodium alginate (SA) pores supported by aramid fiber (AF) networks and surface covered with a dense layer of copper sulfide (CuS) and was fabricated through freeze-drying-cycling alternating immersion method. The internal vertical SA lamellar structure endows the hydrogel with strong water transport capability, while the high photothermal conversion ability of the surface CuS layer enables rapid water evaporation. Therefore, as 2D evaporators, the evaporation rate in highly concentrated salt solutions (15 wt%) is up to 2.07 kg m-2 h-1 under 1.0 sun. As 3D evaporators, efficient evaporation is achieved throughout the day by compensating evaporation at the sides and top. Under the irradiation of 0.2 and 0.8 suns outdoors, the evaporation rate of the 3D evaporator can reach 7.47 kg m-2 h-1 and 12.60 kg m-2 h-1, respectively, and its total evaporation is 4.72 times higher than that of the 2D evaporator. Notably, the hydrogel evaporator has excellent anti-salt properties, antimicrobial properties, and recyclability. This work provides valuable guidance for designing and developing practical hydrogel evaporators.

Achieving "Ion Diode" Salt Resistance in Solar Interfacial Evaporation by a Tesla Valve-Like Water Transport Structure.

Salt deposition is a disturbing problem that limits the development of passive solar-driven interfacial evaporation. Inspired by the passive fluid control mechanism of the Tesla valve, a novel solar evaporator is proposed with a Tesla valve-like water transport structure to prevent salt accumulation at the evaporation interface. A unique "ion diode" salt resistance of this evaporator is significantly achieved by optimizing the two asymmetric water transport structures, consisting of one Tesla valve-like side and one wide-leg side, which establish a reverse-suppressing and forward-accelerating water transport channel. In contrast to the limited ion migration of the typical symmetric solar evaporator, such a channel caused by the water/salt ions transport difference between two water supply structures, reinforces the water/salt ions supply on the wide-leg side, thus leading to an apparent unidirectional salt ions migration from the wide-leg side to bulk water through the Tesla valve-like side. Consequently, an evaporation rate of 3.25kg m-2h-1 and a conversion efficiency of 83.27% under 2suns are achieved in 16wt% NaCl solution. The development of the Tesla Valve-like evaporator provides a new perspective for solving salt deposition and realizing scalable applications of solar-driven interfacial evaporation.