Bilayered Biofoam for Highly Efficient Solar Steam Generation

Hydrodynamic solar-driven interfacial evaporation - Gone with the flow

Evaporation has been one of the most classic desalination processes on the Earth. When we try to use the power of water flow itself, the evaporation process can perform even better. Here, we report a hydrodynamic solar-driven interfacial evaporation process which water evaporation rate can achieve 6.58 kg·m-2·h-1 (over 100 times higher than natural evaporation). A waterwheel-structure solar interfacial evaporator was designed and assembled by printed filter papers. The evaporator can both rapidly distribute solution on the evaporation interface and be hydraulically driven to rotate continuously to improve the evaporation rate by water flow. The hydrodynamic solar-driven interfacial evaporation process successfully overcomes the problem of slow diffusion of water vapor, but also realizes the day-and-night operation of process and the self-cleaning of salt fouling. Apart from the application in solar desalination, the developed evaporator has great potentials in vapor production and salt recovery for industrial use.

Tree-Inspired Aerogel Comprising Nonoxidized Graphene Flakes and Cellulose as Solar Absorber for Efficient Water Generation

As global freshwater shortages worsen, solar steam generation (SSG) emerges as a promising, eco-friendly, and cost-effective solution for water purification. However, widespread SSG implementation requires efficient photothermal materials and solar evaporators that integrate enhanced light-to-heat conversion, rapid water transportation, and optimal thermal management. This study investigates using nonoxidized graphene flakes (NOGF) with negligible defects as photothermal materials capable of absorbing over 98% of sunlight. By combining NOGF with cellulose nanofibers (CNF) through bidirectional freeze casting, we created a vertically and radially aligned solar evaporator. The hybrid aerogel exhibited exceptional solar absorption, efficient solar-to-thermal conversion, and improved surface wettability. Inspired by tree structures, our design ensures rapid water supply while minimizing heat loss. With low NOGF content (∼10.0%), the NOGF/CNF aerogel achieves a solar steam generation rate of 2.39 kg m-2 h-1 with an energy conversion efficiency of 93.7% under 1-sun illumination, promising applications in seawater desalination and wastewater purification.

KOH Activated Carbon Coated 3D Wood Solar Evaporator with Highest Water Transport Height and Evaporation Rate for Clean Water Production

The water evaporation rate of 3D solar evaporator heavily relies on the water transport height of the evaporator. In this work, a 3D solar evaporator featuring a soil capillary-like structure is designed by surface coating native balsa wood using potassium hydroxide activated carbon (KAC). This KAC-coated wood evaporator can transport water up to 32 cm, surpassing that of native wood by ≈8 times. Moreover, under 1 kW m-2 solar radiation without wind, the KAC-coated wood evaporator exhibits a remarkable water evaporation rate of 25.3 kg m-2 h-1, ranking among the highest compared with other reported evaporators. The exceptional water transport capabilities of the KAC-coated wood should be attributed to the black and hydrophilic KAC film, which creates a porous network resembling a soil capillary structure to facilitate efficient water transport. In the porous network of coated KAC film, the small internal pores play a pivotal role in achieving rapid capillary condensation, while the larger interstitial channels store condensed water, further promoting water transport up more and micropore capillary condensation. Moreover, this innovative design demonstrates efficacy in retarding phenol from wastewater through absorption onto the coated KAC film, thus presenting a new avenue for high-efficiency clean water production.

Recent Advances of Bio-Based Hydrogel Derived Interfacial Evaporator for Sustainable Water and Collaborative Energy Storage Applications

Solar interfacial evaporation strategy (SIES) has shown great potential to deal with water scarcity and energy crisis. Biobased hydrogel derived interfacial evaporator can realize efficient evaporation due to the unique structure- properties relationship. As such, increasing studies have focused on water treatment or even potential accompanying advanced energy storage applications with respect of efficiency and mechanism of bio-based hydrogel derived interfacial evaporation from microscale to molecular scale. In this review, the interrelationship between efficient interfacial evaporator and bio-based hydrogel is first presented. Then, special attention is paid on the inherent molecular characteristics of the biopolymer related to the up-to-date studies of promising biopolymers derived interfacial evaporator with the objective to showcase the unique superiority of biopolymer. In addition, the applications of the bio-based hydrogels are highlighted concerning the aspects including water desalination, water decontamination atmospheric water harvesting, energy storage and conversion. Finally, the challenges and future perspectives are given to unveil the bottleneck of the biobased hydrogel derived SIES in sustainable water and other energy storage applications.

Developing Salt-Rejecting Evaporators for Solar Desalination: A Critical Review

Solar desalination, a green, low-cost, and sustainable technology, offers a promising way to get clean water from seawater without relying on electricity and complex infrastructures. However, the main challenge faced in solar desalination is salt accumulation, either on the surface of or inside the solar evaporator, which can impair solar-to-vapor efficiency and even lead to the failure of the evaporator itself. While many ideas have been tried to address this ″salt accumulation″, scientists have not had a clear system for understanding what works best for the enhancement of salt-rejecting ability. Therein, for the first time, we classified the state-of-the-art salt-rejecting designs into isolation strategy (isolating the solar evaporator from brine), dilution strategy (diluting the concentrated brine), and crystallization strategy (regulating the crystallization site into a tiny area). Through the specific equations presented, we have identified key parameters for each strategy and highlighted the corresponding improvements in the solar desalination performance. This Review provides a semiquantitative perspective on salt-rejecting designs and critical parameters for enhancing the salt-rejecting ability of dilution-based, isolation-based, and crystallization-based solar evaporators. Ultimately, this knowledge can help us create reliable solar desalination solutions to provide clean water from even the saltiest sources.

Enhanced solar-driven evaporation and mineral extraction from hypersaline produced water using low-cost microporous photothermal foam

The beneficial reuse of produced water (PW) holds significant promise to alleviate water scarcity. However, it still suffers major limitations associated with the high cost of treatment due to energy consumption, economics of scale, and the complex physiochemical constituents. PW is a hypersaline (TDS ∼ 250,000 mg/l) oilfield water with bio-species, organic matter, anions, divalent cations, and radioactive elements. A sustainable treatment option is solar-driven floating photothermal evaporation (PTE), a desalination technology implemented for seawater characterized by simpler chemical compositions and low salinity. In this work, the photothermal evaporator for PW was fabricated using low-cost commercially available charcoal polyurethane foam. The engineered macrochannels and structural alterations created unique pathways for salt extraction and evaporation; and ensured hydrodynamic balance between the rates of capillary flow and evaporation. This novel design mitigated flooding or dry out on the evaporating surface and kept the system running steadily while simultaneously harvesting freshwater and valuable salts. The key findings from this work are (a) the development of a novel temperature ratio-based method to determine optimum PTE thickness that results in maximum evaporation and thermal localization, (b) the development of the empirical correlation between the rate of thermal localization, evaporation rate, and PTE thickness. It combines the interplay of convection, evaporative flux, conduction, heat capacitance, and thickness on the thermal response of PTE foam to incident solar flux, and (c) experimental evidence revealing efflorescence and subflorescence salt on the evaporating surface and pore, and (d) enhanced evaporation rate of 118 % or 71.6 kg/day-m2 of clean water from chemically complex hypersaline produced water. These findings are significant for the engineering design and estimation of the performance of a PTE in a solar-driven evaporation system.

Synthesis of Hydrophilic Poly(vinylpyrrolidone)/CuS Free-Standing Thin Films Exhibiting Photothermal Conversion

Free-standing films without the need for any support materials attract attention because of their excellent flexibility in use and ability to be transferred to various substrates. However, free-standing films containing large amounts of inorganic crystalline particles are hard to achieve due to their low strength. In this study, we found the possibility of preparing a free-standing composite film of CuS/polyvinylpyrrolidone (PVP) at a large loading of CuS (>50%) from a concentrated colloidal dispersion of CuS nanoparticles modified with PVP. Despite the large amount of inorganic crystals contained in the free-standing film, the film was strong enough to be handled without any support materials. As a proof-of-concept application of the free-standing film, a solar water evaporation experiment was performed. The CuS/PVP free-standing film exhibited photothermal conversion under light illumination to generate heat and accelerate water evaporation, achieving an evaporation rate of 4.35 kg·m-2 h-1 and an evaporation efficiency of 96.3% at a power density of 3 suns. In addition, thanks to the free-standing feature, one side of the CuS/PVP film could be hydrophobized with polydimethylsiloxane to form a Janus thin film, allowing for floating on the water surface. As a result, effective water evaporation was achieved because of the selective evaporation of water from the air/water interface.

Superhydrophobic sand evaporator with core-shell structure for long-term salt-resistant solar desalination

Solar-driven water evaporation, as an environmentally benign pathway, provides an opportunity for alleviating global clean water scarcity. However, the rapidly generated interfacial steam and localized heating could cause increased salt concentration and accumulation, deteriorating the evaporation performance and long-term stability. Herein, a novel superhydrophobic sand solar (FPPSD) evaporator with a core-shell structure was proposed through interface functionalization for continuous photothermal desalination. The collective behavior essence of the sand aggregate gave itself micron-scale self-organized pores and configurable shapes, generating desirable capillary force and supplying effective water-pumping channels. More importantly, combining the dopamine, polypyrrole (PPy), and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTS) through π-π conjugation and multiple hydrogen bonding effects gave the FPPSD evaporator with stable superhydrophobic property and highly efficient photothermal conversion capability. Therefore, the FPPSD evaporator showed a continuous and stable photothermal performance even after 96 h continuous evaporation under 3-sun irradiation for 10 wt% saline solution, among the best values in the reported works of literature, demonstrating its excellent salt-resistance stability. Furthermore, this novel FPPSD evaporator displayed outstanding environmental stability that kept its initial water transport capacity even after being treated under harsh conditions for 30 days. With excellent salt-resistance ability and stable environmental stability, the FPPSD evaporator will provide an attractive platform for sustainable solar-driven water management.

Cellulose-based bi-layer hydrogel evaporator with a low evaporation enthalpy for efficient solar desalination

Interfacial evaporation through hydrogel-based evaporators is emerging as a sustainable and cost-effective strategy for drinkable water production. Herein, a specially designed bi-layer hydrogel evaporator was fabricated and used for efficient solar water desalination. With cotton linter as cellulose precursor, it was dispersed in a highly concentrated ZnCl2 (65 %) solution, and cross-linked by epichlorohydrin to prepare cellulose composite hydrogel. After removing inorganic salts by salt-leaching, polyaniline (PANi) with broadband and wide-range light absorption was then integrated into the top surface of hydrogel through in situ polymerization to construct a bi-layer evaporator. As a solar evaporator, the water could be evaporated with a low-energy demand, and the heat from the sunlight could be confined at the interface to achieve efficient water evaporation. Therefore, the hydrogel evaporator demonstrates an optimal water evaporation rate of 3.02 kg m-2 h-1 and photothermal conversion efficiency of 89.09 % under 1 sun (1 kW m-2) irradiation. This work provides new possibilities for efficient solar water purification systems with assured water quality.

Interfacial Solar Evaporation: From Fundamental Research to Applications

In the last decade, interfacial solar steam generation (ISSG), powered by natural sunlight garnered significant attention due to its great potential for low-cost and environmentally friendly clean water production in alignment with the global decarbonization efforts. This review aims to share the knowledge and engage with a broader readership about the current progress of ISSG technology and the facing challenges to promote further advancements toward practical applications. The first part of this review assesses the current strategies for enhancing the energy efficiency of ISSG systems, including optimizing light absorption, reducing energy losses, harvesting additional energy, and lowering evaporation enthalpy. Subsequently, the current challenges faced by ISSG technologies, notably salt accumulation and bio-fouling issues in practical applications, are elucidated and contemporary methods are discussed to overcome these challenges. In the end, potential applications of ISSG, ranging from initial seawater desalination and industrial wastewater purification to power generation, sterilization, soil remediation, and innovative concept of solar sea farm, are introduced, highlighting the promising potential of ISSG technology in contributing to sustainable and environmentally conscious practices. Based on the review and in-depth understanding of these aspects, the future research focuses are proposed to address potential issues in both fundamental research and practical applications.

Vascular Bundle for Exceptional Water Confinement, Transport, and Evaporation

Nature, through billions of years of evolution, has constructed extremely efficient biosystems for transporting, confining, and vaporizing water. Mankind's ability to master water, however, is far from impeccable, and a sustainable supply of clean fresh water remains a global challenge. Here, we learn from Nature and prepare papyrus carbon (PC) from Egyptian papyrus paper as a sustainable solar desalination material. By taking advantage of the capillary pores from vascular bundles that are inherently built for transporting water in plants, PC achieves an evaporation rate of 4.1 kg m-2 h-1 in a passive single-stage device. Raman spectroscopy and thermal calorimetry show that the capillary pores pose a confinement effect to generate loosely hydrogen-bonded intermediate water, which substantially reduces the enthalpy of vaporization, allowing for exceptionally high energy efficiencies. The understanding is applicable to all nature-designed vascular plants and man-made separation and purification systems.

Engineering High-Tortuosity 3D Gradient Structure and CFD-Assisted Multifield Analysis for Solar Interfacial Evaporation

Solar interfacial evaporation is a promising method for solving the global shortage of fresh water. While 2D evaporators can efficiently localize solar-converted heat at the thin layer of the water-air interface, 3D solar evaporators can maximize energy reutilization while maintaining effective mass transport ability, few studies are conducted to explore the effect of gradient porosity on evaporation performance. In this study, a multifield assisted strategy based on a gradient 3D structure with high tortuosity is proposed, which creates a thermal field environment for efficient evaporation through high absorption of sunlight and excellent photothermal conversion and uses the gradient structure to optimize the internal pressure field to enhance water evaporation and transport. This hierarchically nanostructured solar absorber, with porosity inhomogeneity-induced pressure gradient and optimized temperature management, is a valuable design idea for manufacturing a more efficient 3D solar evaporator in the field of seawater desalination. Owing to the understanding of optimizing the dimension by various simulation parameters, the evaporation efficiencies of such structures are found to be 165.7%, suppressing the most evaporator. Moreover, it can provide new ideas and references for the fields of mass transfer and thermal management.

Carbonaceous Materials-Based Photothermal Process in Water Treatment: From Originals to Frontier Applications

The photothermal process has attracted considerable attention in water treatment due to its advantages of low energy consumption and high efficiency. In this respect, photothermal materials play a crucial role in the photothermal process. Particularly, carbonaceous materials have emerged as promising candidates for this process because of exceptional photothermal performance. While previous research on carbonaceous materials has primarily focused on photothermal evaporation and sterilization, there is now a growing interest in exploring the potential of photothermal effect-assisted advanced oxidation processes (AOPs). However, the underlying mechanism of the photothermal effect assisted by carbonaceous materials remains unclear. This review aims to provide a comprehensive review of the photothermal process of carbonaceous materials in water treatment. It begins by introducing the photothermal properties of carbonaceous materials, followed by a discussion on strategies for enhancing these properties. Then, the application of carbonaceous materials-based photothermal process for water treatment is summarized. This includes both direct photothermal processes such as photothermal evaporation and sterilization, as well as indirect photothermal processes that assisted AOPs. Meanwhile, various mechanisms assisted by the photothermal effect are summarized. Finally, the challenges and opportunities of using carbonaceous materials-based photothermal processes for water treatment are proposed.

Research Advances in Wood Composites in Applications of Industrial Wastewater Purification and Solar-Driven Seawater Desalination

In recent years, the ecosystem has been seriously affected by sewage discharge and oil spill accidents. A series of issues (such as the continuous pollution of the ecological environment and the imminent exhaustion of freshwater resources) are becoming more and more unmanageable, resulting in a crisis of water quality and quantity. Therefore, studies on industrial wastewater purification and solar-driven seawater desalination based on wood composites have been widely considered as an important development direction. This paper comprehensively analyzes and summarizes the applications of wood composites in the fields of solar-driven seawater desalination and polluted water purification. In particular, the present situation of industrial wastewater containing heavy metal ions, microorganisms, aromatic dyes and oil stains and related problems of solar-driven seawater desalination are comprehensively analyzed and summarized. Generally, functional nanomaterials are loaded into the wood cell wall, from which lignin and hemicellulose are selectively removed. Alternatively, functional groups are modified on the basis of the molecular structure of the wood microchannels. Due to its three-dimensional (3D) pore structure and low thermal conductivity, wood is an ideal substrate material for industrial wastewater purification and solar-driven seawater desalination. Based on the study of objective conditions such as the preparation process, modification method and selection of photothermal conversion materials, the performances of the wood composites in filtration, adsorption and seawater desalination are analyzed in detail. In addition, this work points out the problems and possible solutions in applying wood composites to industrial wastewater purification and solar-driven seawater desalination.

Hybrid Aeromaterials for Enhanced and Rapid Volumetric Photothermal Response

Conversion of light into heat is essential for a broad range of technologies such as solar thermal heating, catalysis and desalination. Three-dimensional (3D) carbon nanomaterial-based aerogels have been shown to hold great promise as photothermal transducer materials. However, until now, their light-to-heat conversion is limited by near-surface absorption, resulting in a strong heat localization only at the illuminated surface region, while most of the aerogel volume remains unused. We present a fabrication concept for highly porous (>99.9%) photothermal hybrid aeromaterials, which enable an ultrarapid and volumetric photothermal response with an enhancement by a factor of around 2.5 compared to the pristine variant. The hybrid aeromaterial is based on strongly light-scattering framework structures composed of interconnected hollow silicon dioxide (SiO2) microtubes, which are functionalized with extremely low amounts (in order of a few μg cm-3) of reduced graphene oxide (rGO) nanosheets, acting as photothermal agents. Tailoring the density of rGO within the framework structure enables us to control both light scattering and light absorption and thus the volumetric photothermal response. We further show that by rapid and repeatable gas activation, these transducer materials expand the field of photothermal applications, like untethered light-powered and light-controlled microfluidic pumps and soft pneumatic actuators.

Scalable Ultralight Wood-Inspired Aerogel with Vertically Aligned Micrometer Channels for Highly Efficient Solar Interfacial Desalination

An ultralight material that simultaneously combines remarkably rapid water transportation, highly efficient photothermal conversion, and excellent thermal insulation is highly desired for solar-driven interfacial desalination but was challenging. In this work, inspired by the unique natural structure of wood, we developed an ultralight aerogel by ice-templated synthesis as an integrated interfacial evaporator for solar-driven water production. The interior features vertically aligned biomimetic microscale channels facilitating rapid transportation of water molecules, while an improved photothermal interface allows high solar absorption and conversion via nonradiative relaxation and molecular vibrations. The biomimetic aerogel is ultralight with a density as low as 0.06 g/cm3, especially its fabrication is size- and shape-programmable as a whole and easily scalable. Additionally, the outstanding thermal insulation of the aerogel focuses heat precisely at the evaporation interface, reducing ineffective heat loss, while the uniformly distributed large-sized channels promote the dynamic convection of high concentration salt ions on the evaporator surface. Consequently, the evaporator shows broadband light absorption of 92.7%, leading to a water evaporation rate reaching 4.55 kg m-2 h-1 under 3 simulated solar irradiations, much higher than that of other reported evaporators with randomly distributed pores. This work provides new insight into advanced hybrid aerogels for highly efficient and durable solar-driven interfacial desalination systems.

Natural Cellulose Fiber-Derived Photothermal Aerogel for Efficient and Sustainable Solar Desalination

Aerogels are becoming a promising platform to fabricate photothermal materials for use in solar steam generation (SSG), which have remarkable application potential in solar desalination, due to their excellent thermal management, salt resistance, and considerable water evaporation rate. In this work, a novel photothermal material is fabricated by forming a suspension between sugarcane bagasse fibers (SBF) and poly(vinyl alcohol), tannic acid (TA), and Fe³⁺ solutions via hydrogen bonds of hydroxyl groups. After freeze drying, the fabricated SBF aerogel-based photothermal (SBFAP) material possesses a 3D interconnected porous microstructure, which could enhance water transportation ability, reduce thermal conductivity, and quickly dissolve salt crystals on the SBFAP surface. Thanks to the formation of micro/nanosized complexes between TA and Fe³⁺ ions on the SBFAP material, the SBFAP exhibits high light capture and water evaporation rate (2.28 kg m^-2 h^-1). In particular, due to strong hydrogen bonding and the SBF, the SBFAP material is reinforced, thereby exhibiting excellent structural stability in seawater. Moreover, the high salt tolerance of SBFAP favors its high desalination performance for at least 76 days of continuous evaporation under actual conditions. This research paves the way for the fabrication of natural cellulose fiber-based photothermal materials for application in solar desalination.

3D Janus structure MXene/cellulose nanofibers/luffa aerogels with superb mechanical strength and high-efficiency desalination for solar-driven interfacial evaporation

Interfacial solar steam generation (ISSG) is considered to be an attractive technique to address the water shortage. However, developing a sustainable thermal management, salt rejection, and excellent mechanical strength ISSG device for long-term stability desalination is still a challenge. Herein, a biomass ISSG device with superb mechanical properties was prepared by introducing a luffa sponge as the skeleton and constructing the MXene/cellulose nanofibers (CNFs) aerogels via freeze-drying. The Janus MXene-decorated CNFs/luffa (JMCL) aerogels integrated the multifunction of fast water transport, good thermal management, and efficient photothermal conversion in a single module, to achieve high-efficiency desalination. 3D Janus structure endowed the JMCL aerogel with opposite wettability, which is feasible to construct the localized photothermal generation and self-floating. The mechanical strength of JMCL aerogels is 437 times that of MXene/CNFs aerogels. The JMCL aerogels delivered a water evaporation rate of 1.40 kg m^-2h^-1 and an efficiency of 91.20% under 1 sun illumination. The excellent salt resistance during 24 h working and long-term solar vapor generation of up to 28 days were achieved. The multifunctional JMCL aerogels with 3D Janus structure offer new insights for developing good durability and eco-friendly biopolymer-based steam generators.

3D porous N-doped lignosulfonate/graphene oxide aerogel for efficient solar steam generation and desalination

Solar-driven interfacial evaporation has been considered one of the most promising approaches to tackle the issue of water scarcity. The salt resistance and water transport capacity of solar evaporation materials are essential to evaluate desalination performance. Herein, a 3D-porous N-doped lignosulfonate/graphene oxide (GO) aerogel (NLGA) was facilely prepared by a one-step hydrothermal method. By introducing ethylenediamine (EDA) as a nitrogen source, the wettability and water transport capacity of the aerogel were enhanced; by introducing lignosulfonate (LS), its porous structure was regulated, and its light absorption capability was significantly improved. The obtained aerogel exhibited an outstanding evaporation rate (1.57 kg m^-2 h^-1) and efficiency (95.2 %) under 1 sun illumination, which is significantly better than some reported foam-based solar evaporators. In addition, NLGA maintained a stable evaporation rate over long-term cyclic evaporation without visible salt accumulation on the surface. The good salt rejection performance is due to the rich-pore structure and superhydrophilicity of NGLA, which provides sufficient water supply to dissolve the salts during water evaporation. NLGA has enormous potential as a solar evaporator based on its excellent performance in solar vapor generation.

Fibrous MXene Aerogels with Tunable Pore Structures for High-Efficiency Desalination of Contaminated Seawater

The seawater desalination based on solar-driven interfacial evaporation has emerged as a promising technique to alleviate the global crisis on freshwater shortage. However, achieving high desalination performance on actual, oil-contaminated seawater remains a critical challenge, because the transport channels and evaporation interfaces of the current solar evaporators are easily blocked by the oil slicks, resulting in undermined evaporation rate and conversion efficiency. Herein, we propose a facile strategy for fabricating a modularized solar evaporator based on flexible MXene aerogels with arbitrarily tunable, highly ordered cellular/lamellar pore structures for high-efficiency oil interception and desalination. The core design is the creation of 1D fibrous MXenes with sufficiently large aspect ratios, whose superior flexibility and plentiful link forms lay the basis for controllable 3D assembly into more complicated pore structures. The cellular pore structure is responsible for effective contaminants rejection due to the multi-sieving effect achieved by the omnipresent, isotropic wall apertures together with underwater superhydrophobicity, while the lamellar pore structure is favorable for rapid evaporation due to the presence of continuous, large-area evaporation channels. The modularized solar evaporator delivers the best evaporation rate (1.48 kg m-2 h-1) and conversion efficiency (92.08%) among all MXene-based desalination materials on oil-contaminated seawater.

Exploitation of renewable energy sources for water desalination using biological tools

The emerging impacts of climate change and the growing world population are driving the demand for more food resources and creating an urgent need for new water resources. About 93% of Earth's surface is made up of water bodies, mainly oceans. Seawater attracted a lot of attention in order to be used as a sustainable source of usable water. However, an essential step in harnessing this source of water is desalination. Utilizing renewable sources of energy, biology offers several tools for removal of salts. This article for the first time reviews all currently available biological water desalination tools and compares their efficiency with industrial systems. Bacteria are employed as electrical power generators to provide the energy needed for desalination in microbial desalination cells. Its salt removal efficiency varied from 0.8 to 30 g/L/d. Many strains of algal cells can grow in high concentrations of salts, adsorb and accumulate it inside the cell, and therefore could be used without prior treatment for seawater desalination. This biological tool can yield salt removal efficiency of 0.4-5 g/L/d. Biopolymers are also used for treatment of seawater through enhancing water evaporation as a component of solar steam generators. Despite significant advances in biological water desalination, further modifications and improvements are still needed to make its use sustainable and cost-effective.

Emerging Materials for Interfacial Solar-Driven Water Purification

Solar-driven water purification is considered as an effective and sustainable technology for water treatment using green solar energy. One major goal for practical applications is to improve the solar evaporation performance by the design of novel photothermal materials, with optimized heat localization and water transport pathways to achieve reduced energy consumption for water vaporization. Recently, some emerging materials like polymers, metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and also single molecules were employed to construct novel solar evaporation systems. In this minireview, we present an overview of the recent efforts on materials development for water purification systems. The state-of-the-art applications of these emerging materials for solar-driven water treatment, including desalination, wastewater purification, sterilization and energy production, are also summarized.

A flexible, high-efficiency, and low-cost FeS2@CTS hydrogel film for solar interface water evaporation

Solar interfacial water evaporation to obtain pure water has attracted extensive attention in recent years. In this work, based on the excellent optical property of FeS2 and the cross-linking nanostructure of chitosan (CTS), a FeS2@CTS hydrogel composite film for solar interfacial water evaporation was developed by hydrothermal synthesis and the following composite coating technology. The prepared FeS2@CTS presented high solar absorptivity of 95.27% and fast optical response capability. Under the optimized condition, the evaporation rate of pure water reached 3.34 kg m−2 h−1 and the photothermal conversion efficiency was 103.06% under one sun irradiation. In five runs, the evaporation rate of the FeS2@CTS was stable, indicating the excellent cycle stability. Also, in the desalination test, the stable evaporation rate of 1.74 kg m−2 h−1 was obtained in five runs. Due to the simple preparation method, low cost, and outstanding interfacial evaporation property, this FeS2@CTS indicates great potential for the seawater desalination or other photothermal conversion applications.

Engineered Wood with Hierarchically Tunable Microchannels toward Efficient Solar Vapor Generation

Wood-based solar steam evaporators have been attracting increasing interest due to their great potential for addressing water scarcity by utilizing sustainable materials and energy. However, engineering a 3D porous structure within the wood lumens and its effect on solar vapor evaporation have not yet been well explored. Here, a natural wood-based solar evaporator with hierarchical pores is fabricated by assembling polyvinyl alcohol within the lumens through an ice-templating approach. The polyvinyl alcohol porous network is engineered from vertically aligned microchannels to dendritically bridged pores with a narrowed size of a few micrometers and significantly increased surface area. Although the formation of plenty of microscopic channels increases the capillary force in comparison to the native wood lumen, the morphology change induces a high tortuosity factor of the porous structure, resulting in a reduced water transportation rate as well as an increased contact angle. On the other hand, the high surface area of the engineered wood lumens and the good hydrophilicity of the filled polyvinyl alcohol improve the ratio of the formed intermediate water, contributing to reduced vaporization enthalpy. Consequently, by using polydopamine as the photothermal material, the hierarchically structured polyvinyl alcohol-wood solar evaporator exhibits an evaporation rate of 1.6 kg m^-2 h^-1 under 1 sun irradiation and a high solar evaporation efficiency of up to 107%, which are higher than most of the reported natural-wood-based solar evaporators. Moreover, by exploring the correlation between porous morphology and performance, it has been found that the polyvinyl alcohol-wood composite not only presents an inexpensive and sustainable evaporator but also provides guidelines for designing high-performance steam generation devices.

Fast proton and water transport in ceramic membrane-based magic-angle graphene

Ceramic membranes for energy conversion and storage devices are essential for becoming carbon neutral due to low cost and high stability, but limited by slow proton and water transport. Meanwhile magic-angle graphene with unconventional superconductivity ushers in a new era, properties research of which are in infant stage, urgently longing for specific applications. Herein, we investigate the ionic-conductivity and water-transport properties of ceramic membrane-based magic-angle graphene by choosing proton and water as a proof-of-concept for the first time, discover the twist-angle tuned proton conduction and water transport in ceramic membrane-based magic-angle graphene, demonstrate the faster proton and water transport in magic-angle graphene than that in graphene, and construct an efficient device of protonic ceramic membrane fuel cell based upon the new fast proton-conducting materials of magic-angle graphene. The proton conduction and water transport in magic-angle graphene can be easily tuned by the twist angle, explained by the corresponding potential energy surface. The smaller the twist angle is, and the faster the proton transport is. The protonic migration energy barrier in magic-angle graphene is lower by about 50% than that in graphene. Additionally, the water transport properties in magic-angle graphene can be improved by tuning twist angles. The electrode with magic-angle graphene can provide higher performance of protonic ceramic membrane fuel cells. The present work opens the specific application of ceramic membrane-based magic-angle graphene as new proton-conducting and water-transport materials in energy and environment.

Solar Interface Evaporation System Assisted by Mirror Reflection Heat Collection Based on Sunflower Chasing the Sun

In this study, a photothermal material, C-CP/MnO₂, was prepared by compounding corrugated paper (CP) and MnO₂, with excellent photothermal conversion efficiency. The porous structure and the presence of oxygen-containing functional groups enabled the material to have a good water transport function and a fast vapor escape rate. The special semihollow structure also allowed C-CP/MnO₂ to have better thermal management and an evaporation rate that could reach 2.563 kg m^-2 h^-1 with an efficiency of 98.82% under 1 sun. The continuous arch structure inside C-CP/MnO₂ was able to induce the Marangoni effect to achieve continuous desalination of high-concentration brine. The mirror heat collector achieved efficient light capture on the material surface through multiple reflections of light. This could increase the amount of radiation on the material surface by nearly 80%, and the evaporation rate could reach 4.314 kg m^-2 h^-1 under 1 sun. Moreover, this study demonstrated the light propagation path by simulating the light using Zemax to verify the correctness of the experimental results. Inspired by the sunflower chasing the sun, we designed a chasing heat collection system powered by solar panels to achieve efficient evaporation outdoors. This provided new ideas for further development of solar interface evaporation and also provided guidance for other industrial applications.

Polypyrrole-coated nanocellulose for solar steam generation: A multi-surface photothermal ink with antibacterial and antifouling properties

Solar energy-based steam generation holds immense potential to tackle the problem of 1.1 billion people lacking access to freshwater and 2.7 billion experiencing freshwater scarcity at least one month a year. Efficient, portable, and universal photothermal materials are required for popularity of solar-driven evaporation systems. Herein, a facile one-pot process based on solution-processed vapor phase polymerization is adopted to fabricate polypyrrole-coated cellulose nanocrystals (CNC-PPy). The CNC-PPy dispersed in water is used as an ink (CNC-PPy ink) to create photothermal layers. The developed ink is readily laminated on diverse substrates utilizing a common paintbrush that firmly attached without any delamination after drying. The optimized cellulose membrane (6 coating cycles) presents an excellent evaporation rate of 1.96 Kg m^-2 h^-1 with corresponding light-to-vapor efficiency of 88.92 % at 1 sun. In addition, the CNC-PPy display excellent antibacterial and antifouling properties in powder and laminated forms against E. coli and S. aureus.

Three-Dimensional Artificial Transpiration Structure Based on 1T/2H-MoS2/Activated Carbon Fiber Cloth for Solar Steam Generation

The rise of solar steam generation is an effective strategy to mitigate clean water shortages. However, achieving further improvements in conversion efficiency and stability remains a challenge. Here, 1T/2H-MoS₂ nanosheets were uniformly assembled on activated carbon fiber cloth (A-CFC) through a facial hydrothermal method, and a three-dimensional (3D)-artificial transpiration device (ATD) was prepared using the plant transpiration process. The combination of activated carbon fiber cloth and 1T/2H phase MoS₂ exhibits high light absorption (∼97.5%), excellent mechanical stability, large evaporation area, and easy escape of vapor. Additionally, the 3D hollow cone of the MoS₂/carbon fiber cloth can effectively reduce radiative and convective energy loss and then achieve the enhancement of energy collection from the environment. An outstanding evaporation rate of 1.61 kg·m^-2·h^-1 with an optimum conversion efficiency of 97% under one sun is reached. Based on the facile fabrication, excellent stability, and high solar conversion efficiency, this nature-inspired design of 3D 1T/2H-MoS₂/A-CFC is expected to facilitate large-scale applications for seawater purification and desalination.

Engineering van der Waals Materials for Advanced Metaphotonics

The outstanding chemical and physical properties of 2D materials, together with their atomically thin nature, make them ideal candidates for metaphotonic device integration and construction, which requires deep subwavelength light-matter interaction to achieve optical functionalities beyond conventional optical phenomena observed in naturally available materials. In addition to their intrinsic properties, the possibility to further manipulate the properties of 2D materials via chemical or physical engineering dramatically enhances their capability, evoking new science on light-matter interaction, leading to leaped performance of existing functional devices and giving birth to new metaphotonic devices that were unattainable previously. Comprehensive understanding of the intrinsic properties of 2D materials, approaches and capabilities for chemical and physical engineering methods, the resulting property modifications and novel functionalities, and applications of metaphotonic devices are provided in this review. Through reviewing the detailed progress in each aspect and the state-of-the-art achievement, insightful analyses of the outstanding challenges and future directions are elucidated in this cross-disciplinary comprehensive review with the aim to provide an overall development picture in the field of 2D material metaphotonics and promote rapid progress in this fast emerging and prosperous field.

A bioinspired solar evaporator with a horizontal channel-like framework for efficient and stable high-salinity brine desalination

In recent years, solar steam generation has been one of the most promising and sustainable techniques for water desalination. However, the heat loss to bulk water dramatically decreases the evaporation rate. Besides, salt deposition on the evaporation surface during brine treatment limits the long-term operation of evaporators. Herein, solar evaporators with a horizontal channel-like framework are reported and high efficiency and outstanding salt resistance are achieved. Firstly, eggplants with a hollow fiber alignment structure were carbonized as CEP evaporators. The CEP-H evaporator with a horizontal fiber growth direction shows a high evaporation efficiency of 90.6% and excellent salt resistance when treating high-salinity brine (20 wt%). The low thermal conductivity perpendicular to the fiber growth direction impedes the conductive heat transfer into bulk water, and fast water transport along the fiber growth direction is beneficial for salt resistance. In addition, a proof-of-concept evaporator polypyrrole-coated polypropylene hollow fiber membrane with a horizontal channel-like framework (PPy/PP-H) has also been developed. This hollow fiber membrane shows a high evaporation rate of 1.64 kg m^-2 h^-1 due to multiangle evaporation and also demonstrates excellent salt-resisting performance for high-salinity brine treatment (20 wt%). The study demonstrates the effect of the horizontal channel-like framework for high evaporation performance and salt resistance, providing new insights into the solar evaporator design for seawater desalination and wastewater treatment.

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.

A bilayer solar evaporator with all-in-one design for efficient seawater desalination

Bilayer solar evaporator combines high photothermal conversion capacity and low heat loss, has become the new darling in interfacial solar steam generation (ISSG). However, the bilayer structure generally achieved by introducing a photothermal coating on the substrate is not conducive to long-term use due to the poor stability of coating. Herein, a fully biomass-based bilayer evaporator is all-in-one designed, using chitosan (CS) as building blocks and CS derived N, S - doped porous carbon (NSPC) as fillers via pre-freezing and freeze-drying. This facile method could realise the quantitative addition of photothermal materials and controllably regulate the structure of the bilayer evaporator, making the structural optimisation readily available. The optimised evaporator exhibits a remarkable evaporation rate of 2.51 kg m^-2h^-1. After 1000 times of pressing, it still maintains at 2.42 kg m^-2h^-1. Additionally, the evaporator displays outstanding long-lasting stability, excellent salt-resistant and degradability. More importantly, a solar desalination device is fabricated for harvesting freshwater outdoor. The daily water production per unit area (4.55 kg) meets the consumption of two adults. This work provides a controllable synthesis strategy of bilayer evaporators for handling global freshwater shortages.

Fibrous Aerogels for Solar Vapor Generation

Solar-driven vapor generation is emerging as an eco-friendly and cost-effective water treatment technology for harvesting solar energy. Aerogels are solid materials with desirable high-performance properties, including low density, low thermal conductivity, and high porosity with a large internal surface, which exhibit outstanding performance in the area of solar vapor generation. Using fibers as building blocks in aerogels could achieve unexpected performance in solar vapor generation due to their entangled fibrous network and high surface area. In this review, based on the fusion of the one-dimensional fibers and three-dimensional porous aerogels, we discuss recent development in fibrous aerogels for solar vapor generation based on building blocks synthesis, photothermal materials selection, pore structures construction and device design. Thermal management and water management of fibrous aerogels are also evaluated to improve evaporation performance. Focusing on materials science and engineering, we overview the key challenges and future research opportunities of fibrous aerogels in both fundamental research and practical application of solar vapor generation technology.

Transpiration-powered desalination water bottle

Inspired by mangrove trees, we present a theoretical design and analysis of a portable desalinating water bottle powered by transpiration. The bottle includes an annular fin for absorbing solar heat, which is used to boost the evaporation rate of water from the interior synthetic leaf. This synthetic leaf comprises a nanoporous film deposited atop a supporting micromesh. Water evaporating from the leaf generates a highly negative Laplace pressure, which pulls the overlying source water across an upstream reverse osmosis membrane. Evaporated water is re-condensed in the bottom of the bottle for collection. The benefit of our hybrid approach to desalination is that reverse osmosis is spontaneously enabled by transpiration, while the thermal evaporation process is enhanced by heat localization and made more durable by pre-filtering the salt. We estimate that a 9.4 cm diameter bottle, with a 10 cm wide annular fin, could harvest about a liter of fresh water per day from ocean water.

Superelastic Clay/Silicone Composite Sponges and Their Applications for Oil/Water Separation and Solar Interfacial Evaporation

3D porous materials are of great interest in many areas of study, but it is still difficult to prepare those with high elasticity and low thermal conductivity via facile methods. Here, superelastic laponite/silicone (LS) composite sponges with low thermal conductivity are prepared via a simple approach. The LS sponges were analyzed by various characterization methods. The content of laponite nanosheets in LS sponges has a great influence on the microstructure, comprehensive mechanical properties, and thermal conductivity. LS sponges feature (i) high mechanical strength, compressibility, and elasticity, (ii) excellent superhydrophobicity/superoleophilicity, and (iii) low thermal conductivity. Consequently, LS sponges could be used for water purification, for example, oil/water separation and solar-driven interfacial evaporation in combination with carbon nanotubes (CNTs). The LS/CNTs solar evaporator has a remarkable evaporation rate of 1.77 kg m^-2 h^-1 for the 3.5 wt % NaCl aqueous solution under 1 kW m^-2 irradiation and high salt resistance. We foresee that this study will promote the development of new 3D porous materials and their applications.

Enhancing solar steam generation using a highly thermally conductive evaporator support

Interfacial solar steam generation is an efficient water evaporation technology which has promising applications in desalination, sterilization, water purification and treatment. A common component of evaporator design is a thermal-insulation support placed between the photothermal evaporation surface and bulk water. This configuration, common in 2-dimensional (2D) evaporation systems, minimizes heat loss from evaporation surface to bulk water, thus localizing the heat on the evaporation surface for efficient evaporation. This design is subsequently directly adopted for 3-dimensional (3D) evaporators without any consideration if it is appropriate. However, unlike 2D solar evaporators, the 3D evaporators can also harvest additional energy (other than solar light) from the air and bulk water to enhance evaporation rate. In this scenario, the use of thermal insulator support is not proper since it will hinder energy extraction from water. Here, the traditional 3D evaporator configuration was completely redesigned by using a highly thermally conductive material, instead of a thermal insulator, to connect evaporation surfaces and the bulk water. Much higher evaporation rates were achieved by this strategy, owing to the rapid heat transfer from the bulk water to the evaporation surfaces. Indoor and outdoor tests both confirmed that evaporation performance could be significantly improved by substituting a thermal insulator with thermally conductive support. These findings will redirect the future design of 3D photothermal evaporators.

Biomimetic Hybridization of Janus-like Graphene Oxide into Hierarchical Porous Hydrogels for Improved Mechanical Properties and Efficient Solar Desalination Devices

Light-absorbing hydrogels provide a means for rapidly evaporating water by using solar energy. However, to achieve light-absorbing hydrogels with both durable mechanical properties and efficient energy utilization remains challenging due to the weak interface interactions between solar absorbers and a hydrogel matrix and difficultly controlled surface topography of swollen hydrogel-based evaporators. Herein, we demonstrate an effective nanoconfinement strategy to assemble a spongy poly(vinyl alcohol)/Janus-like graphene oxide hybrid hydrogel (SPJH) via strong interfacial interactions of hydrogen bonding and hydrophobic interaction. The resultant SPJHs with an intriguing hierarchical microstructure templated by air bubbles and ice crystals showed a high toughness (∼231 kJ m^-2) and ultimate strain (∼310%) that were more than three times as high as those of light-absorbing hydrogels and a high evaporation rate of 4.18 kg m^-2 h^-1 with an efficiency up to 95% under 1 sun irradiation (relative humidity = 20%; temperature = 25 °C), achieved by synergistic mechanical and energy nanoconfinement and tailored surface topography within the designed hybrid hydrogels. This hybrid hydrogel-based solar evaporator with an ingenious design principle provides a pathway for scalable and processable solar water purification devices.

Metal-free functionalized carbonized cotton for efficient solar steam generation and wastewater treatment

Water desalination via solar steam generation is one of the most important technologies to address the increasingly pressing global water scarcity. Materials for solar photothermal energy conversion are highly sought after for their cost savings, environmental friendliness and broad utility in many applications including domestic water heating and solar-driven desalination. Herein, we report the successful development of metal-free, low weight and cost effective functionalized carbonized cotton (CC) fibers for efficient solar water desalination and wastewater treatment. The CC fibers with nearly full solar spectrum absorption, efficient photo-thermal conversion and low-cost could provide excellent alternatives to the high-cost plasmonic-based materials for solar water desalination. We also report on a novel and simple device to mitigate the issues associated with conductive heat loss by utilizing the economically viable carbonized cotton materials as an irradiation surface placed on a low-density polyethylene foam that floats on the surface of seawater. The CC solar steam generation device exhibits average water evaporation rates of 0.9, 6.4 and 10.9 kg m^-2 h^-1 with impressive solar-to-vapor efficiencies of 59.2, 88.7 and 94.9% under 1, 5 and 8 sun illumination, respectively. Moreover, the device displays excellent durability showing stable evaporation rates over 10 steam generation cycles under 5 sun of solar intensity. Furthermore, the applicability of the CC device for the removal of organic dyes from contaminated water through solar steam generation is also demonstrated. The low-cost, simple design, high solar thermal evaporation efficiency, excellent stability and long-term durability make this CC device a perfect candidate for applications in seawater desalination and wastewater treatment by solar steam generation.

Carbon Materials for Solar Water Evaporation and Desalination

Seawater desalination is viewed as a promising solution to world freshwater scarcity. Solar assisted desalination is proposed to overcome the high energy consumption in current desalination technologies, as it uses abundant and sustainable solar energy as the only energy input. Interfacial solar vapor generation (SVG) has attracted considerable research interest due to its high energy conversion efficiency, simple implementation, and cost-effectiveness. Among all the candidate materials for solar evaporators, carbon-based materials stand out due to their intrinsic high solar absorption, highly tunable structure, easy preparation, low cost, and earth-abundancy. In this review, the recent progress on carbon-based materials for the development of interfacial SVG is summarized. First, a brief introduction to the basic design principles of the interfacial SVG system is presented. Then, recent efforts in carbon-based solar evaporators, from artificial structures to bioinspired configurations, focusing on their structure-function relationship are highlighted. Strategies for designing antisalt-fouling desalination systems are also summarized. Last, the challenges and opportunities of carbon-based materials for solar evaporation technology are elaborated.

Flexible, affordable and environmentally sustainable solar vapor generation based on ferric tannate/bacterial cellulose composite for efficient desalination solutions

Desalination by solar steam generation (SSG) system is a green technology to produce pure water, which can address the issue of water scarcity. A novel photothermal material for the SSG system was fabricated by immersing bacterial cellulose (BC) sequentially into tannic acid (TA) and iron(iii) (Fe³⁺) solutions. Surface analysis of the resulting BC–TA–Fe³⁺ (BTF) material showed that coordination nanocomplexes between Fe³⁺ and hydroxyl groups of TA were formed on the surface of cellulose nanofibers. BTF material exhibited high sunlight absorption (∼95%), hydrophilic, self-cleaning properties, and excellent structural stability. SSG systems based on BTF had an evaporation efficiency of 91% and an evaporation rate of 1.56 kg m⁻² h⁻¹ under 1 sun illumination. Then, an efficient desalination device based on the larger-scale BTF material was fabricated to produce freshwater, the amount of freshwater per day was 5.6 kg m⁻² on a sunny day. BTF material, thus, showed great potential in seawater desalination applications along with simple, versatile, scalable, and affordable fabrication methods.

The BTF material showed a great potential for seawater desalination applications along with a simple, versatile, scalable, and affordable fabrication method.

Progress of photothermal membrane distillation for decentralized desalination: A review

The conventional membrane distillation (MD) process is accompanied by large energy consumption, low thermal efficiency and inevitable requirements of centralized infrastructures, which impede its practical applications, especially in the offshore and remote off-grid areas. Thanks to the rapid development of efficient photothermal materials over the last decade, a new photothermal membrane distillation (PMD) process has emerged to harness abundant solar energy and localize heating on the membrane-feed water interface via photothermal effects. Driven by the temperature difference across the PMD membrane, water vapor can be generated on the membrane-feed surface, transported through membrane pores and condensed at permeate side to obtain freshwater, thus tackling the challenge of obtaining clean water using green energy. The PMD process avoids heating the entire bulk feed water and feed transportation from heat units to membrane modules, which save substantial amounts of energy. The interfacial localized heating intrinsically mitigates the temperature polarization across the membrane. The latent heat from vapor condensation can be effectively recovered via multi-level PMD configurations. As great efforts have been made to exploit PMD process, it is imperative to review the state-of-the-art progress of PMD and shed light on its future trend. Here, we briefly illustrate PMD mechanisms and membrane requirements, photothermal materials feasible for developing PMD membranes along with their light-to-heat mechanisms. This is followed by reviewing diverse approaches to prepare PMD membranes, which are classified into one-step fabrication and multi-step modification methods. Comprehensive discussion about PMD membrane performance in different configurations and their small pilot-scaled applications are provided. The effects of operational parameters and module designs are discussed in Section 6. Finally, the current challenges and future perspectives of PMD process are emphasized with the aim of providing guidance for future works.

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.