Surface Patterning of Two-Dimensional Nanostructure-Embedded Photothermal Hydrogels for High-Yield Solar Steam Generation

A lignin-derived carbon dot-upgraded bacterial cellulose membrane as an all-in-one interfacial evaporator for solar-driven water purification

Solar-driven interfacial evaporation has emerged as an efficient approach for wastewater treatment and seawater desalination. New trends demand adaptive technology to develop photothermal membranes with multifunctional features. Herein, we report a robust multi-purpose near-infrared (NIR)-active hydrogel composite (c-BC@N-LCD) from broad-spectrum active nitrogen-doped lignin-derived carbon dots (N-LCDs) covalently cross-linked with a bacterial cellulose (BC) matrix. BC provides adequate porosity and hydrophilicity required for easy water transport while managing heat loss. A commendable evaporation rate (ER) of 2.2 kg m-2 h-1 under one sun (1 kW m-2) is achieved by c-BC@N-LCD. The developed hydrogel system is also found to be efficient for desalination (∼2.1 kg m-2 h-1) and for remediating various pollutants (heavy metal ions, dyes, and pharmaceuticals) from feed water. The efficacy of the membrane remains unaltered by different grades of water, and hence can be adoptable for economically stressed communities living in water-polluted regions as well as those residing in coastal areas.

Fully Integrated Biosensing System for Dynamic Monitoring of Sweat Glucose and Real-Time pH Adjustment Based on 3D Graphene MXene Aerogel

The development of noninvasive glucose sensors capable of continuous monitoring without restricting user mobility is crucial, particularly for managing diabetes, which demands consistent and long-term observation. Traditional sensors often face challenges with accuracy and stability that curtail their practical applications. To address these issues, we have innovatively applied a three-dimensional porous aerogel composed of Ti3C2Tx MXene and reduced graphene oxide (MX-rGO) in electrochemical sensing. It significantly reduces the electron-transfer distance between the enzyme's redox center and the electrode surface while firmly anchoring the enzyme layer to effectively prevent any leakage. Another pivotal advancement in our study is the integration of the sensor with a real-time adaptive calibration mechanism tailored specifically for analyzing sweat glucose. This sensor not only measures glucose levels but also dynamically monitors and adjusts to pH fluctuations in sweat. Such capabilities ensure the precise delivery of physiological data during physical activities, providing strong support for personalized health management.

Tortuosity Engineering of Water Channels to Customized Water Supply for Enhancing Hydrogel Solar Evaporation

Hydrogel as a solar evaporator shows great potential in freshwater production. However, hydrogels often lead to an imbalance between solar energy input and water supply management due to their excessively high saturated water content. Thus, achieving a stable water-energy-balance in hydrogel evaporators remains challenging. Here, by tortuosity engineering designed water transport channels, a seamless high-tortuosity/low-tortuosity/high-tortuosity structured hydrogel (SHLH structure hydrogel) evaporator is developed, which enables the hydrogel with customized water transport rate, leading to the controlled water supply at the evaporator interface. An excellent equilibrium between the photothermal conversion and water supply is established, and the maximum utilization of solar energy is realized, thereby achieving an excellent evaporation rate of 3.64 kg m-2 h-1 under one solar illumination. This tortuosity engineering controlled SHLH structured evaporator provides a novel strategy to attain water-energy-balance and expands new approaches for constructing hydrogel-based evaporators with tailored water transportation capacity.

Low vaporization enthalpy of modified chitosan hydrogel for high performance solar evaporator

The high vaporization enthalpy of water attributed to the strong hydrogen bonds between water molecules is limiting the performance of solar evaporators. This work demonstrates a deliberate attempt to significantly reduce the vaporization enthalpy of water through the introduction of weak water-amine hydrogen bond interactions in hydrogel evaporators. In this article, bio-based chitosan-agarose/multiwalled carbon nanotube hydrogel film evaporators (CAMFEs) exhibit larger vaporization enthalpy reduction with the presence of primary amine groups in chitosan. An interplay between vaporization enthalpy reduction and water diffusivity leads to an optimal ratio of chitosan to agarose = 7:1 (CAMFE7) showing an impressive evaporation rate of 4.13 kg m-2 h-1 under 1 sun irradiation. CAMFE7 also exhibits excellent salt resistance, with a stable water evaporation rate, using brine water of up to 10 % salinity under continuous 1 sun irradiation. The high mechanical robustness together with its scalability makes CAMFE7 a highly promising material for practical drinking water production.

Recent innovations in 3D solar evaporators and their functionalities

Interfacial solar evaporation (ISE) has emerged as a promising technology to alleviate global water scarcity via energy-efficient purification of both wastewater and seawater. While ISE was originally identified and developed during studies of simple double-layered two-dimensional (2D) evaporators, observed limitations in evaporation rate and functionality soon led to the development of three-dimensional (3D) evaporators, which is now recognized as one of the most pivotal milestones in the research field. 3D evaporators significantly enhance the evaporation rates beyond the theoretical limits of 2D evaporators. Furthermore, 3D evaporators could have multifaceted functionalities originating from various functional evaporation surfaces and 3D structures. This review summarizes recent advances in 3D evaporators, focusing on rational design, fabrication and energy nexus of 3D evaporators, and the derivative functions for improving solar evaporation performance and exploring novel applications. Future research prospects are also proposed based on the in-depth understanding of the fundamental aspects of 3D evaporators and the requirements for practical applications.

Combined effect of grooves and nanoflower structured Co3O4 coating on bamboo wood for highly efficient solar steam generation at indoor and outdoor conditions

Currently, interfacial solar steam generation (ISSG) in desalinating water has become very popular for obtaining purified water from polluted water. However, finding an efficient evaporator with low cost is a challenging task for researchers. In this work, we introduce natural bamboo wood (BW) that acts as an interfacial evaporator for obtaining purified water. Four different wood evaporators namely, flat wood (BW-FW), two-cut grooved wood (BW-2G), four-cut grooved wood (BW-4G), and four-cut grooved with Co3O4-coated wood (BW-4G/Co3O4) are used to study the mass loss (ML), evaporation rate (ER), and evaporation efficiency (EY). From the observations, BW-4G/Co3O4 gives an admirable ML, ER, and EY of 4.4 g, 3.366 kg m-2 h-1, and 91.34% under 1 sun illumination for 60 min. Also, the BW-4G/Co3O4 evaporator is kept under natural sun illumination. It achieves 17.8 g of ML, 1.92 kg m-2 h-1 of ER, and 76% of EY respectively under 604.762 W/m2 solar illumination for 8 h. The reasons for the observed results are as follows: (i) the presence of grooves increases the exposing area for solar illuminations, (ii) super hydrophilicity nature of wood gives continuous replenishment of water from the bottom to the evaporative surface, (iii) the excellent salt rejection property of wood aids in continuous water transportation without salt accumulations. As a result of the condensed seawater samples, the ion concentrations (zinc, magnesium, cadmium, lead, copper, and sodium) come under WHO standards. Consequently, it gives better dye water separation from polluted water.

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.

Hierarchical Ti3C2/BiVO4 microcapsules for enhanced solar-driven water evaporation and photocatalytic H2 evolution

Desalination processes frequently require a lot of energy to generate freshwater and energy, which depletes resources. Their reliance on each other creates tension between these two vital resources. Herein, hierarchical MXene nanosheets and bismuth vanadate (Ti3C2/BiVO4)-derived microcapsules were synthesized for a photothermal-induced photoredox reaction for twofold applications, namely, solar-driven water evaporation and hydrogen (H2) production. For this purpose, flexible aerogels were fabricated by introducing Ti3C2/BiVO4 microcapsules in the polymeric network of natural rubber latex (NRL-Ti3C2/BiVO4), and a high evaporation rate of 2.01 kg m-2 h-1 was achieved under 1-kW m-2 solar intensity. The excellent performance is attributed to the presence of Ti3C2/BiVO4 microcapsules in the polymeric network, which provides balanced hydrophilicity and broadband sun absorption (96 %) and is aimed at plasmonic heating with microscale thermal confinement tailored by heat transfer simulations. Notably, localized plasmonic heating at the catalyst active sites of the Ti3C2/BiVO4 heterostructure promotes enhanced photocatalytic H2 production evolved after 4 h of reaction is 9.39 μmol, which is highly efficient than pure BiVO4 and Ti3C2. This method turns the issue of water-fuel crisis into a collaborative connection, presenting avenues to collectively address the anticipated demand rather than fostering competition.

Fluid Unidirectional Transport Induced by Structure and Ambient Elements across Porous Materials: From Principles to Applications

Spontaneous or nonspontaneous unidirectional fluid transport across multidimension can occur under specific structural designs and ambient elements for porous materials. While existing reviews have extensively summarized unidirectional fluid transport on surfaces, there is an absence of literature summarizing fluid's unidirectional transport across porous materials. This review introduces wetting phenomena observed on natural biological surfaces or porous structures. Subsequently, it offers an overview of diverse principles and potential applications in this field, emphasizing various physical and chemical structural designs (surface energy, capillary size, topographic curvature) and ambient elements (underwater, under oil, pressure, and solar energy). Applications encompass moisture-wicking fabric, sensors, skincare, fog collection, oil-water separation, electrochemistry, liquid-based gating, and solar evaporators. Additionally, significant principles and formulas from various studies are compelled to offer readers valuable references. Simultaneously, potential advantages and challenges are critically assessed in these applications and the perspectives are presented.

Numerical Simulation Technologies in Solar-Driven Interfacial Evaporation Processes

Solar interfacial evaporation technology has the advantages of environmentally conscious and sustainable benefits. Recent research on light absorption, water transportation, and thermal management has improved the evaporation performance of solar interfacial evaporators. However, many studies on photothermal materials and structures only aim to improve performance, neglecting explanations for heat and mass transfer coupling or providing evidence for performance enhancement. Numerical simulation can simulate the diffusion paths and heat and water transfer processes to understand the thermal and mass transfer mechanism, thereby better achieving the design of efficient solar interfacial evaporators. Therefore, this review summarizes the latest exciting findings and tremendous advances in numerical simulation for solar interfacial evaporation. First, it presents a macroscopic summary of the application of simulation in temperature distribution, salt concentration distribution, and vapor flux distribution during evaporation. Second, the utilization of simulation in the microscopic is summed up, specifically focusing on the movement of water molecules and the mechanisms of light responses during evaporation. Finally, all simulation methods have the goal of validating the physical processes in solar interfacial evaporation. It is hoped that the use of numerical simulation can provide theoretical guidance and technical support for the application of solar-driven interfacial evaporation technology.

Helical Micropillar Processed by One-Step 3D Printing for Solar Thermal Conversion

Solar thermal utilization has broad applications in a variety of fields. Currently, maximizing the photo-thermal conversion efficiency remains a research hotspot in this field. The exquisite plant structures in nature have greatly inspired human structural design across many domains. In this work, inspired by the photosynthesis of helical grass, a HM type solar absorber made in graphene-based composite sheets is used for solar thermal conversion. The unique design promoted more effective solar energy into thermal energy through multiple reflections and scattering of solar photons. Notably, the Helical Micropillar (HM) is fabricated using a one-step projection 3D printing process based on a special 3D helical beam. As a result, the solar absorber's absorbance value can reach 0.83 in the 400-2500 nm range, and the surface temperature increased by ≈128.3% relative to the original temperature. The temperature rise rate of the solar absorber reached 22.4 °C min-1, demonstrating the significant potential of the HM in practical applications of solar thermal energy collection and utilization.

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.

Enhancing Solar Steam Generation of Hydrogels via Silver Nanoparticle-Doped Cellulose Nanofibers

Solar steam generation (SSG) is regarded as an efficient approach for harnessing solar energy to purify polluted or saline water. Herein, we demonstrate a hydrogel composed of cellulose nanofibers (CNFs), polyethylenimine (PEI), and reduced graphene oxide (rGO) that functions as an independent solar steam generator, which shows enhanced solar water evaporation efficiency by incorporating silver nanoparticles (AgNPs). It presented that the presence of AgNPs increases the photothermal conversion efficiency and thermal conductivity of the evaporator and reduces the enthalpy of evaporation. As a result, an outstanding water evaporation rate of 3.62 kg m-2 h-1 and a photothermal conversion efficiency of 96.25% are successfully obtained under one sun illumination. Also, the resulting hydrogel exhibits exceptional mechanical properties, as well as outstanding desalination and salt-resistant abilities during prolonged seawater desalination. In oil/water mixtures, the evaporation of the hydrogel decreases to 2.94 kg m-2 h-1, owing to the oil layer barrier. This work paves a reference approach to produce easily addressed cellulose nanofiber (CNF)-based hydrogel evaporators with significantly enhanced evaporation rates.

Synergistic effects of hydrophilic function group and micropores on water evaporation in a novel carbon hydrogels for efficient solar steam generation

Solar steam generation (SSG) using hydrogels is emerging as a promising technology for clean water production. Herein, a novel oxygen-doped microporous carbon hydrogel (OPCH), rich in hydrophilic groups and micropores, has been synthesized from microalgae to optimize SSG. OPCH outperforms hydrogels with hydrophobic porous carbon or nonporous hydrophilic biochar, significantly reducing water's evaporation enthalpy from 2216.06 to 1107.88 J g-1 and activating 42.3 g of water per 100 g for evaporation, resulting in an impressive evaporation rate of 2.44 kg m-2 h-1 under one sun. A detailed investigation into the synergistic effects of hydrophilic groups and micropores on evaporation via a second derivative thermogravimetry method revealed two types of bonded water contributing to enthalpy reduction. Molecular dynamics simulations provided further insights, revealing that the hydrophilic micropores considerably decrease both the number and the lifetime of hydrogen bonds among water molecules. This dual effect not only reduces the energy barrier for evaporation but also enhances the kinetic energy needed for the phase transition, significantly boosting the water evaporation process. The sustained high evaporation rates of OPCH, observed across multiple cycles and under varying salinity conditions, underscore its potential as a highly efficient and sustainable solution for SSG applications.

Quasi-waffle solar distiller for durable desalination of seawater

Water purification via interfacial solar steam generation exhibits promising potential. However, salt crystallization on evaporators reduces solar absorption and obstructs water supply. To address it, a waffle-shaped solar evaporator (WSE) has been designed. WSE is fabricated via a zinc-assisted pyrolysis route, combining low-cost biomass carbon sources, recyclable zinc, and die-stamping process. This route enables cost-effective production without the need of sophisticated processing. As compared to conventional plane-shaped evaporators, WSE is featured by extra sidewalls for triggering the convection with the synergistic solute and thermal Marangoni effects. Consequently, WSE achieves spontaneous salt rejection and durable evaporation stability. It has demonstrated continuous operation for more than 60 days in brine without fouling.

Hydrogel-Based Interfacial Solar-Driven Evaporation: Essentials and Trails

Hydrogel-based interfacial solar-driven evaporation (ISDE) gives full play to the highly adjustable physical and chemical properties of hydrogel, which endows ISDE systems with excellent evaporation performance, anti-pollution properties, and mechanical behavior, making it more promising for applications in seawater desalination and wastewater treatment. This review systematically introduces the latest advances in hydrogel-based ISDE systems from three aspects: the required properties, the preparation methods, and the role played in application scenarios of hydrogels used in ISDE. Additionally, we also discuss the remaining challenges and potential opportunities in hydrogel-based ISDE systems. By summarizing the latest research progress, we hope that researchers in related fields have some insight into the unique advantages of hydrogels in the ISDE field and contribute our efforts so that ISDE technology reaches the finishing line of practical application on the hydrogel track.

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.

Anisotropic MXene/Poly(vinyl alcohol) Composite Hydrogels with Vertically Oriented Channels and Modulated Surface Topography for Efficient Solar-Driven Water Evaporation and Purification

Hierarchical structure and surface topography play pivotal roles in developing high-performance solar-driven evaporators for clean water production; however, there exists a notable gap in research addressing simultaneous modulation of internal microstructure and surface topography in hydrogels to enhance both solar steam generation performance and desalination efficiency. Herein, anisotropic poly(vinyl alcohol)/MXene composite hydrogels for efficient solar-driven water evaporation and wastewater purification are fabricated using a template-assisted directional freezing approach followed by precise surface wettability modulation. The resultant composite hydrogels exhibit vertically oriented channels that ensure fast water supply during evaporation, and their poly(vinyl alcohol) skeletons can reduce the vaporization enthalpy of the water in the hydrogels. The incorporation of MXene sheets enables efficient solar light absorption and solar-thermal conversion while providing structural reinforcement to the hydrogels. More importantly, the as-created undulating solar-thermal surface, featuring modulated hydrophilic troughs and hydrophobic crests, significantly enhances solar-thermal conversion efficiency, thereby boosting solar evaporation performances. As a result, the fabricated hydrogel-based evaporator exhibits an impressive evaporation rate of 2.55 kg m-2 h-1 under 1 sun irradiation, coupled with long-term durability and desalination stability. Notably, the outstanding mechanical robustness of the hydrogel further enables high portability through a readily achievable process of reversible dehydration/hydration.

Anion-Counterion Strategy toward Organic Cocrystal Engineering for Near-Infrared Photothermal Conversion and Solar-Driven Water Evaporation

An anion-counterion strategy is proposed to construct organic mono-radical charge-transfer cocrystals for near-infrared photothermal conversion and solar-driven water evaporation. Ionic compounds with halogen anions as the counterions serve as electron donors, providing the necessary electrons for efficient charge transfer with unchanged skeleton atoms and structures as well as the broad red-shifted absorption (200-2000 nm) and unprecedented photothermal conversion efficiency (~90.5 %@808 nm) for the cocrystals. Based on these cocrystals, an excellent solar-driven interfacial water evaporation rate up to 6.1±1.1 kg ⋅ m-2  ⋅ h-1 under 1 sun is recorded due to the comprehensive evaporation effect from the cocrystal loading in polyurethane foams and chimney addition, such performance is superior to the reported results on charge-transfer cocrystals or other materials for solar-driven interfacial evaporation. This prototype exhibits the great potential of cocrystals prepared by the one-step mechanochemistry method in practical large-scale seawater desalination applications.

Boron nanosheets boosting solar thermal water evaporation

Hydrogel-based solar vapour generators (SVGs) are promising for wastewater treatment and desalination. The performance of SVG systems is governed by solar thermal conversion and water management. Progress has been made in achieving high energy conversion efficiency, but the water evaporation rates are still unsatisfactory under 1 sun irradiation. This study introduced novel two-dimensional (2D) boron nanosheets as additives into hydrogel-based SVGs. The resulting SVGs exhibit an outstanding evaporation rate of 4.03 kg m-2 h-1 under 1 sun irradiation. This significant improvement is attributed to the 2D boron nanosheets, which leads to the formation of a higher content of intermediate water and reduced water evaporation enthalpy to 845.11 kJ kg-1. The SVGs into which boron nanosheets were incorporated also showed high salt resistance and durability, demonstrating their great potential for desalination applications.

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.

Functional MXenes: Progress and Perspectives on Synthetic Strategies and Structure-Property Interplay for Next-Generation Technologies

MXenes are a class of 2D materials that include layered transition metal carbides, nitrides, and carbonitrides. Since their inception in 2011, they have garnered significant attention due to their diverse compositions, unique structures, and extraordinary properties, such as high specific surface areas and excellent electrical conductivity. This versatility has opened up immense potential in various fields, catalyzing a surge in MXene research and leading to note worthy advancements. This review offers an in-depth overview of the evolution of MXenes over the past 5 years, with an emphasis on synthetic strategies, structure-property relationships, and technological prospects. A classification scheme for MXene structures based on entropy is presented and an updated summary of the elemental constituents of the MXene family is provided, as documented in recent literature. Delving into the microscopic structure and synthesis routes, the intricate structure-property relationships are explored at the nano/micro level that dictate the macroscopic applications of MXenes. Through an extensive review of the latest representative works, the utilization of MXenes in energy, environmental, electronic, and biomedical fields is showcased, offering a glimpse into the current technological bottlenecks, such asstability, scalability, and device integration. Moreover, potential pathways for advancing MXenes toward next-generation technologies are highlighted.

Boosting interfacial solar steam generation by three-dimensional bilayer cellulose aerogels

Interfacial solar steam generation (ISSG) provides a sustainable approach of clean water production through desalination and water purification. It is still needed to pursue a fast evaporation rate, high-quality freshwater production, and low-cost evaporators. Herein, a three-dimensional (3D) bilayer aerogel was fabricated using cellulose nanofiber (CNF) as a skeleton filled with polyvinyl alcohol phosphate ester (PVAP), and carbon nanotubes (CNT) as a light absorbing material in the top layer. The CNF/PVAP/CNT aerogel (CPC) had broadband light absorption ability and exhibited an ultrafast water transfer rate. The lower thermal conductivity of CPC effectively confined the convert heat in the top surface and minimized heat loss. Additionally, a large amount of intermediate water caused by water activation decreased the evaporation enthalpy. Under 1 sun irradiation, the CPC-3 (3.0 cm height of CPC) achieved a high evaporation rate of 4.02 kg m-2 h-1 with an energy conversion efficiency of 125.1%. The additional convective flow and environmental energy made CPC achieve an ultrahigh evaporation rate of 11.37 kg m-2 h-1, surpassing 673% of the solar input energy. More importantly, the continuous solar desalination and higher evaporation rate (10.70 kg m-2 h-1) in seawater revealed that CPC was a promising candidate for practical desalination. Outdoor cumulative evaporation was up to 73.2 kg m-2 d-1 in weak sunlight and lower temperature, which would meet the daily drinking water demands of 20 people. The excellent cost-effectiveness of 1.085 L h-1 $-1 presented its potential for a wide range of practical applications, such as solar desalination, wastewater treatment, and metal extractions.

Simultaneous photothermal and photocatalytic MOF- derived C/TiO2 composites for high-efficiency solar driven purification of sewage

Solar-driven water evaporation is a promising technology of freshwater production to address the water scarcity. However, the photothermal material and the distilled water would be contaminated in the evaporation of wastewater including organic pollutants. In this work, MOF-derived C/TiO2 composites (carbonized UiO-66-NH2 (Ti)) with simultaneous photothermal and photocatalytic functions are designed for producing freshwater from sewage. With advantageous features of porous structure with large specific area, excellent sunlight absorption and super-hydrophilicity, the carbonized UiO-66-NH2 (Ti) layer exhibits high water evaporation efficiency of 94% under 1.0 sun irradiation. Meanwhile, the layer can simultaneously decompose the organic pollutants with degradation efficiency of 92.7% in the underlying water during solar-driven water evaporation. This bifunctional material will provide a new approach for solar-driven water evaporation and photocatalytic degradation of organic pollutant synergistically.

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

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

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.

Water Activation in Solar-Powered Vapor Generation

Solar-powered vapor evaporation (SVG), based on the liquid-gas phase conversion concept using solar energy, has been given close attention as a promising technology to address the global water shortage. At molecular level, water molecules escaping from liquid water should overcome the attraction of the molecules on the liquid surface layer to evaporate. For this reason, it is better to reduce the energy required for evaporation by breaking a smaller number of hydrogen bonds or forming weak hydrogen bonds to ensure efficient and convenient vapor production. Many novel evaporator materials and effective water activation strategies have been proposed to stimulate rapid steam production and surpass the theoretical thermal limit. However, an in-depth understanding of the phase/enthalpy change process of water evaporation is unclear. In this review, a summary of theoretical analyses of vaporization enthalpy, general calculations, and characterization methods is provided. Various water activation mechanisms are also outlined to reduce evaporation enthalpy in evaporators. Moreover, unsolved issues associated with water activation are critically discussed to provide a direction for future research. Meanwhile, significant pioneering developments made in SVG are highlighted, hoping to provide a relatively entire chain for more scholars who are just stepping into this field.

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

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

Flatband λ-Ti3O5 towards extraordinary solar steam generation

Solar steam interfacial evaporation represents a promising strategy for seawater desalination and wastewater purification owing to its environmentally friendly character1-3. To improve the solar-to-steam generation, most previous efforts have focused on effectively harvesting solar energy over the full solar spectrum4-7. However, the importance of tuning joint densities of states in enhancing solar absorption of photothermal materials is less emphasized. Here we propose a route to greatly elevate joint densities of states by introducing a flat-band electronic structure. Our study reveals that metallic λ-Ti3O5 powders show a high solar absorptivity of 96.4% due to Ti-Ti dimer-induced flat bands around the Fermi level. By incorporating them into three-dimensional porous hydrogel-based evaporators with a conical cavity, an unprecedentedly high evaporation rate of roughly 6.09 kilograms per square metre per hour is achieved for 3.5 weight percent saline water under 1 sun of irradiation without salt precipitation. Fundamentally, the Ti-Ti dimers and U-shaped groove structure exposed on the λ-Ti3O5 surface facilitate the dissociation of adsorbed water molecules and benefit the interfacial water evaporation in the form of small clusters. The present work highlights the crucial roles of Ti-Ti dimer-induced flat bands in enchaining solar absorption and peculiar U-shaped grooves in promoting water dissociation, offering insights into access to cost-effective solar-to-steam generation.

Synergistic Dual-Mechanism Localized Heat Channeling and Spectrum-Tailored Liquid Metal Hydrogels for Efficient Solar Water Evaporation and Desalination

Photothermal hydrogels featuring broadband light absorption abilities and highly hydrated networks provide an appealing mass-energy transfer platform for water evaporation by using solar energy. However, the targeted delivery of solar heat energy to power the water evaporation process remains challenging. Herein, enlightened by metal-phenolic coordination chemistry and camouflaged architecture, photothermal hydrogels with dual-mechanism vaporization structure are tactfully designed via a rational interfacial engineering and integration strategy to enable near-µm heat confinement and highly efficient light-to-heat conversion ability. The spectrum-tailored liquid metal droplet (LMGAs-FeIII ) and optimized carbon-wrapped silver nanowire sponge (Ag@C750 ) are integrally built as photothermal promotors/channels and jointly embedded into a highly hydratable poly(vinyl alcohol) hydrogel, denoted as PALGH, to synergistically boost water molecule activation and interfacial vaporization behavior by triggering robust photothermal performance. As a result, under one sun irradiation, the all-embracing PALGH hydrogel evaporation system achieves a brine evaporation rate to a high level of 3.47 kg m-2 h-1 , and >19 L m-2 clean water of PALGH is ideally delivered daily when purifying natural seawater. This work offers not only a rational design principle to create sophisticated photothermal materials but also replenishes insight into solar heat generation and water transportation in a cross-media system.

Environmental energy enhanced solar-driven evaporator with spontaneous internal convection for highly efficient water purification

Solar-driven interfacial evaporation for water purification is limited by the structural design of the solar evaporator and, more importantly, by the inability to separate the water from volatile organic compounds (VOCs) present in the water source. Here, we report a three-dimensional (3D) bifunctional evaporator based on N-doped carbon (CoNC/CF), which enables the separation of fresh water from VOCs by activating PMS during the evaporation process with a VOC removal rate of 99%. There is abundant van der Waals interaction between peroxymonosulfate (PMS) and CoNC/CF, and pyrrolic N is confirmed as the active site for binding phenol, thus contributing to the separation of phenol from water. With the advantageous features of sufficient light absorption, adequate water storage capacity, and spontaneous internal convection flow on its top surface, the 3D evaporator achieves a high evaporation rate under one sun (1 kW/m2) at 3.16 kg/m2/h. More notably, through careful structural design, additional energy from the environment and water can be utilized. With such a high evaporation rate and satisfactory purification performance, this work is expected to provide a promising platform for wastewater treatment.

Ultrathin Water Layer Conservation by "Nano-forest" in a Three-Dimensional Interface Regulates Energy Flow to Boost Solar Evaporation

Solar-driven interfacial evaporation technology utilizes materials to form a thin layer on the water's surface, absorbs sunlight on this layer, completes the light-to-heat conversion, heats up the water, and vaporizes it. This greatly reduces energy loss to bulk water and greatly improves the evaporation rate for producing clean water. Additionally, three-dimensional (3D) evaporators are increasingly being applied in this field, and the cold surface generated by the rapid evaporation in the 3D evaporator can utilize environmental heat to achieve a net energy gain for the system. Both strategies improve the evaporation rate of the system, but 3D materials typically have high water contents and cannot avoid energy flow into non-evaporated water. To address this, we introduce the advantages of interfacial evaporation into 3D evaporation by constructing an evaporator with a highly conductive copper core skeleton and an outer layer of ultrathin water and by reasonably constructing interconnected evaporation frameworks. Investigating and optimizing the mutual influence of the ultrathin water layer on the framework, an evaporator with 40 pores per inch (ppi) can reach a maximum of 24.4 kg·m-2 h-1, indicating that 3D interfacial evaporators with ultrathin water layers concentrate energy flow to stimulate high evaporation rates. This strategy will promote the development of photothermal evaporation technology.

Mechanochemistry toward Organic "Salt" via Integer-Charge-Transfer Cocrystal Strategy for Rapid, Efficient, and Scalable Near-Infrared Photothermal Conversion

Inspired by the concept of ionic charge-transfer complexes for the Mott insulator, integer-charge-transfer (integer-CT) cocrystals are designed for NIR photo-thermal conversion (PTC). With amino-styryl-pyridinium dyes and F4TCNQ (7,7',8,8'-Tetracyano-2,3,5,6-tetrafluoroquinodimethane) serving as donor/acceptor (D/A) units, integer-CT cocrystals, including amorphous stacking "salt" and segregated stacking "ionic crystal", are synthesized by mechanochemistry and solution method, respectively. Surprisingly, the integer-CT cocrystals are self-assembled only through multiple D-A hydrogen bonds (C-H⋅⋅⋅X (X=N, F)). Strong charge-transfer interactions in cocrystals contribute to the strong light-harvesting ability at 200-1500 nm. Under 808 nm laser illumination, both the "salt" and "ionic crystal" display excellent PTC efficiency beneficial from ultrafast (∼2 ps) nonradiative decay of excited states. Thus integer-CT cocrystals are potential candidates for rapid, efficient, and scalable PTC platforms. Especially amorphous "salt" with good photo/thermal stability is highly desirable in practical large-scale solar-harvesting/conversion applications in water environment. This work verifies the validity of the integer-CT cocrystal strategy, and charts a promising path to synthesize amorphous PTC materials by mechanochemical method in one-step.

Overview of Solar Steam Devices from Materials and Structures

The global shortage of freshwater supply has become an imminent problem. The high energy consumption of traditional desalination technology cannot meet the demand for sustainable energy development. Therefore, exploring new energy sources to obtain pure water has become one of the effective ways to solve the freshwater resource crisis. In recent years, solar steam technology which utilizes solar energy as the sole input source for photothermal conversion has shown to be sustainable, low-cost, and environmentally friendly, providing a viable low-carbon solution for freshwater supply. This review summarizes the latest developments in solar steam generators. The working principle of steam technology and the types of heating systems are described. The photothermal conversion mechanisms of different materials are illustrated. Emphasis is placed on describing strategies to optimize light absorption and improve steam efficiency from material properties to structural design. Finally, challenges in the development of solar steam devices are pointed out, aiming to provide new ideas for the development of solar steam devices and alleviate the shortage of freshwater resources.

A decellularized lung extracellular matrix/chondroitin sulfate/gelatin/chitosan-based 3D culture system shapes breast cancer lung metastasis

Distal metastasis of breast cancer is a primary cause of death, and the lung is a common metastatic target of breast cancer. However, the role of the lung niche in promoting breast cancer progression is not well understood. Engineered three-dimensional (3D) in vitro models capable of bridging this knowledge gap can be specifically designed to mimic crucial characteristics of the lung niche in a more physiologically relevant context than conventional two-dimensional systems. In this study, two 3D culture systems were developed to mimic the late stage of breast cancer progression at a lung metastatic site. These 3D models were created based on a novel decellularized lung extracellular matrix/chondroitin sulfate/gelatin/chitosan composite material and on a porcine decellularized lung matrix (PDLM), with the former tailored with comparable properties (stiffness, pore size, biochemical composition, and microstructure) to that of the in vivo lung matrix. The different microstructure and stiffness of the two types of scaffolds yielded diverse presentations of MCF-7 cells in terms of cell distribution, cell morphology, and migration. Cells showed better extensions with apparent pseudopods and more homogeneous and reduced migration activity on the composite scaffold compared to those on the PDLM scaffold. Furthermore, alveolar-like structures with superior porous connectivity in the composite scaffold remarkably promoted aggressive cell proliferation and viability. In conclusion, a novel lung matrix-mimetic 3D in vitro breast cancer lung metastasis model was developed to clarify the underlying correlativity between lung ECM and breast cancer cells after lung colonization. A better understanding of the effects of biochemical and biophysical environments of the lung matrix on cell behaviors can help elucidate the potential mechanisms of breast cancer progression and further improve target discovery of therapeutic strategies.

Insight into the Charge-Ratio-Tuned Solar Vapor Generation of Polyion Complex Hydrogel/Coal Powder Composites

Solar-driven water purification has been deemed a promising technology to address the issue of clean water scarcity. However, traditional solar distillers often suffer from low evaporation rates under natural sunlight irradiation, while the high costs of the fabrication of photothermal materials further hinders their practical applications. Here, through the harnessing of the complexation process of oppositely charged polyelectrolyte solutions, a polyion complex hydrogel/coal powder composite (HCC)-based highly efficient solar distiller is reported. In particular, the influence of the charge ratio of polyanion-to-polycation on the solar vapor generation performance of HCC has been systematically investigated. Together with a scanning electron microscope (SEM) and the Raman spectrum method, it is found that a deviation from the charge balance point not only alters the microporous structure of HCC and weakens its water transporting capabilities, but also leads to a decreased content of activated water molecules and enlarges the energy barrier of water evaporation. As a result, HCC prepared at the charge balance point exhibits the highest evaporation rate of 3.12 kg m^-2 h^-1 under one sun irradiation, with a solar-vapor conversion efficiency as high as 88.83%. HCC also exhibits remarkable solar vapor generation (SVG) performance for the purification of various water bodies. In simulated seawater (3.5 wt% NaCl solutions), the evaporation rate can be as high as 3.22 kg m^-2 h^-1. In acid and alkaline solutions, HCCs are capable of maintaining high evaporation rates of 2.98 and 2.85 kg m^-2 h^-1, respectively. It is anticipated that this study may provide insights for the design of low-cost next-generation solar evaporators, and broaden the practical applications of SVG for seawater desalination and industrial wastewater purification.

Eco-friendly photothermal hydrogel evaporator for efficient solar-driven water purification

The field of solar vapor generation has developed rapidly in recent years, but achieving the goals of a high evaporation rate, eco-friendliness and rapid preparation with low-cost raw materials is still a challenge. In this work, a type of photothermal hydrogel evaporator was prepared by blending eco-friendly poly(vinyl alcohol), agarose, Fe³⁺ and tannic acid (TA) together, in which the tannic acid-ferric ion (TA*Fe³⁺) complexes served as photothermal materials and effective gelators. The results indicate that the TA*Fe³⁺ complex exhibits excellent gelatinization ability and light-absorption performance, which leads to a compressive stress of 0.98 MPa at 80% strain and up to 85% light absorption ratio in the photothermal hydrogel. For interfacial evaporation, a high rate of 1.897 ± 0.11 kg·m^-2·h^-1 corresponding to an energy efficiency of 89.7 ± 2.73% under 1 sun irradiation is achieved. Moreover, the hydrogel evaporator exhibits high stability in a 12-hour test and a 20-cycle test without a decline in evaporation performance. The outdoor testing results show that the hydrogel evaporator can achieve an evaporation rate of > 0.70 kg/m² and effectively purify wastewater treatment and seawater desalination.

Photothermal Nanomaterials: A Powerful Light-to-Heat Converter

All forms of energy follow the law of conservation of energy, by which they can be neither created nor destroyed. Light-to-heat conversion as a traditional yet constantly evolving means of converting light into thermal energy has been of enduring appeal to researchers and the public. With the continuous development of advanced nanotechnologies, a variety of photothermal nanomaterials have been endowed with excellent light harvesting and photothermal conversion capabilities for exploring fascinating and prospective applications. Herein we review the latest progresses on photothermal nanomaterials, with a focus on their underlying mechanisms as powerful light-to-heat converters. We present an extensive catalogue of nanostructured photothermal materials, including metallic/semiconductor structures, carbon materials, organic polymers, and two-dimensional materials. The proper material selection and rational structural design for improving the photothermal performance are then discussed. We also provide a representative overview of the latest techniques for probing photothermally generated heat at the nanoscale. We finally review the recent significant developments of photothermal applications and give a brief outlook on the current challenges and future directions of photothermal nanomaterials.

Improved Photo-Excited Carriers Transportation of WS2 -O-Doped-Graphene Heterostructures for Solar Steam Generation

Two-dimensional (2D) transition metal dichalcogenides and graphene have revealed promising applications in optoelectronic and energy storage and conversion. However, there are rare reports of modifying the light-to-heat transformation via preparing their heterostructures for solar steam generation. In this work, commercial WS₂ and sucrose are utilized as precursors to produce 2D WS₂ -O-doped-graphene heterostructures (WS₂ -O-graphene) for solar water evaporation. The WS₂ -O-graphene evaporators demonstrate excellent average water evaporation rate (2.11 kg m^-2  h^-1 ) and energy efficiency (82.2%), which are 1.3- and 1.2-fold higher than WS₂ and O-doped graphene-based evaporators, respectively. Furthermore, for the real seawater with different pH values (pH 1 and 12) and rhodamine B pollutants, the WS₂ -O-graphene evaporators show great average evaporation rates (≈2.08 and 2.09 kg m^-2  h^-1 , respectively) for producing freshwater with an extremely low-grade of dye residual and nearly neutral pH values. More interestingly, due to the self-storage water ability of WS₂ -O-graphene evaporators, water evaporation can be implemented without the presence of bulk water. As a result, the evaporation rate reaches 3.23 kg m^-2  h^-1 , which is ≈1.5 times higher than the regular solar water evaporation system. This work provides a new approach for preparing 2D transition metal dichalcogenides and graphene heterostructures for efficient solar water evaporation.

Sulfonated PAM/PPy Cryogels with Lowered Evaporation Enthalpy for Highly Efficient Photothermal Water Evaporation

Because of the increasing scarcity of water resources, the desalination of seawater by photothermal evaporation with harvested solar energy has gradually become a popular research topic. The interconnected macroporous cryogel prepared from polymerization and crosslinking below the freezing temperature of the reactant solution has an excellent performance in photothermal water evaporation after loading photothermal materials. In this study, polyacrylamide (PAM) cryogels were prepared by cryo-polymerization and sulfonated in an alkaline solution containing formaldehyde and Na₂SO₃. Importantly, the evaporation enthalpy of water in sulfonated PAM cryogel was reduced to 1187 J·g^-1 due to the introduction of sulfonate groups into PAM, which was beneficial to increase the photothermal evaporation rate and efficiency. The sulfonated PAM cryogels loaded with polypyrrole and the umbrella-shaped melamine foam substrate were combined to form a photothermal evaporation device, and the evaporation rate was as high as 2.50 kg·m^-2·h^-1 under one-sun radiation. Meanwhile, the evaporation rate reached 2.09 kg·m^-2·h^-1 in the 14 wt% high-concentration saline solution, and no salt crystals appeared on the surface of the cryogel after 5 h of photothermal evaporation. Therefore, it was evidenced that the presence of sulfonate groups not only reduced the evaporation enthalpy of water but also prevented salting-out from blocking the water delivery channel during photothermal evaporation, with a sufficiently high evaporation rate, providing a reliable idea of matrix modification for the design of high-efficiency photothermal evaporation materials.

Efficient Fabrication of Micro/Nanostructured Polyethylene/Carbon Nanotubes Foam with Robust Superhydrophobicity, Excellent Photothermality, and Sufficient Adaptability for All-Weather Freshwater Harvesting

The integration of fog collection and solar-driven evaporation has great significance in addressing the challenge of the global freshwater crisis. Herein, a micro/nanostructured polyethylene/carbon nanotubes foam with interconnected open-cell structure (MN-PCG) is fabricated using an industrialized micro extrusion compression molding technology. The 3D surface micro/nanostructure provides sufficient nucleation points for tiny water droplets to harvest moisture from humid air and a fog harvesting efficiency of 1451 mg cm^-2 h^-1 is achieved at night. The homogeneously dispersed carbon nanotubes and the graphite oxide@carbon nanotubes coating endow the MN-PCG foam with excellent photothermal properties. Benefitting from the excellent photothermal property and sufficient steam escape channels, the MN-PCG foam attains a superior evaporation rate of 2.42 kg m^-2 h^-1 under 1 Sun illumination. Consequently, a daily yield of ≈35 kg m^-2 is realized by the integration of fog collection and solar-driven evaporation. Moreover, the robust superhydrophobicity, acid/alkali tolerance, thermal resistance, and passive/active de-icing properties provide a guarantee for the long-term work of the MN-PCG foam during practical outdoor applications. The large-scale fabrication method for an all-weather freshwater harvester offers an excellent solution to address the global water scarcity.

Facile fabrication of Ni5P4-NiMoOx nanorod arrays with synergistic thermal management for efficient interfacial solar steam generation and water purification

Interfacial steam generation by harnessing renewable solar energy has been recognized as a sustainable solution to global freshwater crisis. A promising evaporator with key components of high spectral absorption, efficient thermal management and adequate water transport is highly desired. In the present study, an integrated design for three-in-one functionality is achieved by simply loading Ni₅P₄-NiMoO_x (P-NMO) on a macroporous nickel foam (NF) carrier. In situ embedding broadband Ni₅P₄ absorber into insulating NiMoO_x enables efficient photothermal conversion and heat localization. Benefiting from proper thermal management and abundant water transmission, P-NMO/NF exhibits the excellent performance for interfacial steam generation with a high evaporation rate of 1.49 kg m^-2h^-1 and evaporation efficiency of 93.0 % under one sun irradiation. Furthermore, the obtained P-NMO/NF is proven to be applicable for high-efficiency freshwater production in seawater desalination and wastewater purification, showing great potential for practical solar evaporator under natural environmental conditions.

Multifunctional Ti3C2 decorated perovskite La1-xSrxCoO3 nanorods for efficient energy conversion

The exploitation of functional materials is paramount for the development of renewable energy to alleviate the storage of freshwater and energy. Herein, a series of perovskites, La_1-xSr_xCoO₃ (LSC), were prepared by a facile hydrothermal and calcination method, in which the oxygen evolution reaction (OER) activity was facilitated with the composition of x = 0.1. Moreover, the two-dimensional (2D) Ti₃C₂ MXene dopant was introduced to boost the functions of electrocatalytic oxygen evolution capability and solar thermal evaporation performance. Strong interfacial interaction and prominent charge-transfer between the La_1-xSr_xCoO₃ and Ti₃C₂ MXene accelerate the redox process of perovskite La_1-xSr_xCoO₃. The obtained La_0.9Sr_0.1CoO₃/Ti₃C₂ MXene (LSM) composite acquired an overpotential of 330 mV at 10 mA cm^-2 in 1 M KOH electrolyte while maintaining remarkable durability. The lower Tafel slope of 83.9 mV per decade for the OER was also achieved, comparable to that of the commercial RuO₂ catalyst. In addition, the LSM exhibited a high solar-evaporation conversion efficiency of 96.8% under 1 sun irradiation, which demonstrated the multi-functionality of this composite. Hence, by presenting high performance in energy conversion of perovskite-derived materials, this work demonstrates their great potential in practical applications for solar driven desalination and highly active electrocatalysis technologies.

Fabrication and Application of Ag, Black TiO2 and Nitrogen-Doped 3D Reduced Graphene Oxide (3D Black TiO2/Ag/N@rGO) Evaporator for Efficient Steam Generation

The scarcity of fresh water, which is aggravated by rapid economic development and population growth, is a major threat to the modern world. Solar-driven interfacial desalination and steam generation is a promising strategy that localizes heat at the air-water interface through appropriate thermal management and demonstrates efficient photothermal performance. In the current study, Ag, black TiO2, and nitrogen-doped 3D reduced graphene oxide (3D black TiO2/Ag/N@rGO) hierarchical evaporator was fabricated, and its morphology, elemental composition, porosity, broadband solar absorption potential, photothermal performance, and interfacial desalination potential were assessed. The 3D solar evaporator showed efficient solar absorption over the entire broadband UV-visible near-infrared (UV-Vis NIR) region and demonstrated 99% photothermal conversion efficiency and potential freshwater generation of 1.43 kg·m−2 h−1. The specific surface area and porosity analyses demonstrated an ultrahigh specific surface area, high pore volume, and a mesoporous structure, with a predominant pore diameter of 4 nm. The strong photothermal performance can be attributed to the nitrogen doping of the rGO, which boosted the electrocatalytic and photothermal activity of the graphene through the activation of the excess free-flowing π electrons of the sp2 configuration of the graphene; the broadband solar absorption potential of the black TiO2; and the localized surface plasmon resonance effect of the AgNPs, which induced hot electron generation and enhanced photothermal conversion. Hence, the high photothermal conversion efficiency attained can be attributed to the synergistic photothermal performances of the individual components and the high interfacial surface area, abundant heat, and mass transfer microcavities of the 3D hierarchical porous solar absorber, offering multiple reflections of light and enhanced solar absorption. The study highlights the promising potential of the 3D evaporator for real-word interfacial desalination of seawater, helping to solve the water shortage problem sustainably.

Wooden Solar Evaporator Design Based on the Water Transpiration Principle of Trees

The double-sided carbonization of poplar with different sections forms a three-layer structure inspired by tree water transpiration. A photothermal evaporation comparison experiment was conducted to simulate the influence of solar radiation intensity (1 kW·m^-2) on uncarbonized and single- and double-sided carbonized poplar specimens. The tissue structure, chemical functional group changes, and profile density of the specimens were analyzed using scanning electron microscopy, Fourier transform infrared spectrometry, and X-ray profile density testing, respectively. The results showed that the tissue structure of the specimen changed after treatment, and the relationship of water evaporation was shown as follows: cross-section (C) > Radial section (R) > Tangential section (T), and Double-sided carbonized poplar (DCP) > Single-sided carbonized poplar (SCP) > Non-carbonized poplar (NCP). Of these, the maximum photothermal evaporation was from the cross-section of the double-sided carbonized poplar (NCPC) with a value of 1.32 kg·m^-2·h^-1, which was 21.97% higher than single-sided carbonized poplar (SCPC) and 37.88% higher than non-carbonized poplar (NCPC). Based on the results, double-sided carbonization three-layer structure treatment can improve the evaporation force of the poplar interface, thereby improving the moisture migration ability of wood, and can be applied to solar interface absorber materials.

3D carbonized grooved straw with efficient evaporation and salt resistance for solar steam generation

Solar steam generation (SSG) is considered an effective solution to the global shortage of freshwater resources. To solve the practical application challenges of SSG in remote outdoor environments where electricity is scarce, it is of great importance to developing new solar evaporators. In this study, a three-dimensional (3D) biochar solar evaporator based on carbonized grooved straw was prepared from agricultural waste corn straw, which had high solar energy conversion efficiency and excellent salt resistance. The existence of grooves increases the surface area to absorb more sunlight and makes the light multilevel reflection improve the evaporation rate. The excellent light absorption, super hydrophilic, and heat shielding properties of 3D carbonized grooved straw resulted in a good evaporation rate (1.57 kg⋅m^-2·h^-1) and energy efficiency (85.9%) under 1 sun irradiation. The 3D grooved biochar solar distiller also demonstrated efficient formation evaporation performance and excellent salt resistance in practical applications in seawater desalination and surface water purification. The 3D grooved biochar solar distiller prepared from agricultural waste has the advantages of being economical and environmentally friendly, with good application prospects.

Hofmeister Effect-Enhanced Hydration Chemistry of Hydrogel for High-Efficiency Solar-Driven Interfacial Desalination

Solar-driven water evaporation technology holds great potential for mitigating the global water scarcity due to its high energy conversion efficiency. Lowering the vaporization enthalpy of water is key to boost the performance of solar-driven desalination. Herein, a highly hydratable hydrogel (PMH) network, consisting of modified needle coke as photothermal material and polyvinyl alcohol (PVA) as hydratable matrix, is crafted via simple physical cross-linking method. When capitalizing on the PMH as evaporator for 3.5 wt% NaCl solution, a high evaporation rate of 3.18 kg m^-2  h^-1  under one sun illumination is deliver ed, unexpectedly outperforming that in pure water (2.53 kg m^-2  h^-1 ). More importantly, the PMH shows a robust desalination durability, thus enabling a self-cleaning system. Further investigations reveal that the outstanding evaporation performance of PMH in brine roots in its hydrability tuned by chaotropic Cl^- , wherein the Cl^- can mediate the hydration chemistry of PVA in PMH and suppress related crystallinity, thus contributing to the increased content of intermediate water and the lowered vaporization enthalpy of brine. This work first scrutinizes the Hofmeister effect on the evaporation behavior of PMH evaporator in brine and provides insights for high-efficiency solar-driven interfacial desalination.