High Evaporation Rates Research Articles

Ultra-high solar steam generation based on regulated water management strategy in 3D biomass hydrogels inspired by the “binding effect” of cell walls

Facing the global challenge of water scarcity, solar-driven seawater desalination has been emerged as a green, non-polluting and sustainable technology, but the practical application of existing solar evaporators was hindered by their low evaporation efficiency and poor mechanical property. Inspired by the binding effect of cell walls, a novel and high-efficiency three-dimensional (3D) evaporator (CDs/CF/CS-LF) was constructed, in which loofah (LF) served as a natural 3D skeleton to support the hydrogel evaporator, resisted deformation, and created an efficient dual water supply mode with the chitosan (CS) hydrogel ensuring that the evaporator maintains high evaporation rate even under high salt environment. Additionally, the cellulose nanofibers (CF) filler enhanced the mechanical property of the hydrogel, ensuring shape stability under pressure impact, and carbon dots (CDs) facilitated the aggregation and cross-linking of chitosan chains through hydrogen bonds, further improving the mechanical property of the evaporator, while also enhancing the photothermal conversion capability of the 3D-CDs/CF/CS-LF evaporator as a photothermal material. The experimental results indicated that the 3D-CDs/CF/CS-LF evaporator could achieve an ultra-high solar vapor production rate of 8.08 kg m−2 h−1 under 1 sunlight intensity in 3.5 wt% NaCl solution. Outdoor seawater desalination experiments demonstrated the utility of 3D-CDs/CF/CS-LF evaporator for practical applications. This work provided a new approach for the improvement of CS-based evaporators and demonstrated their potential application in seawater desalination and purification.

Carbon black and polyetherimide modified ES nonwovens for low-cost and continuous seawater desalination

Solar-powered desalination is considered a promising and sustainable method for producing clean water to alleviate freshwater shortages. However, most solar evaporators have drawbacks such as high costs, complicated processes and lack of durability. Here, we present solar evaporators modified with polyethyleneimine and gallic acid, decorated with carbon black nonwovens, for desalination to produce clean water. The carbon black photothermal nonwovens were produced by treating ES hot air nonwovens with a spray of carbon black solution. Utilizing the light-absorbing heat generation of carbon black and the skin-core structural characteristics of ES(PE/PET) nonwoven, the carbon black is firmly embedded in the PE skin layer of the nonwoven fabric. Subsequently, mussel chemistry inspired the formation of polyethyleneimine and gallic acid coatings on the surface of the carbon black-loaded nonwoven. By combining carbon black with mussel coatings, the photothermal nonwovens demonstrated improved hydrophilicity, excellent photothermal water evaporation performance, and enhanced light conversion efficiency. The modified interfacial evaporator exhibited a high evaporation rate of 1.22 kg m−2·h−1 and had high cost-effectiveness of 332.4 g·h−1·$−1. In addition, reusing, desalination, and outdoor experiments were conducted to showcase the potential of the evaporator for practical desalination. This work demonstrates the significant potential of photothermal ES nonwovens for efficient solar-driven clean water production to tackle global freshwater shortages.

High-Efficiency Photothermal Water Evaporation under Low-Intensity Sunlight Using Wood Biochar Monolith.

Utilizing energy directly from the sun, solar water evaporation drives the global hydrological cycle and produces freshwater from saline water in the oceans and on land. As water is a poor solar absorber, a photothermal material is needed to facilitate the conversion of photons to thermal energy and increase the efficiency of solar desalination. However, the current photothermal materials are less efficient and expensive to be manufactured. Inspired by nature, we created a new photothermal material called a wood biochar monolith (WBM) by carbonizing wood using the pyrolysis process at 1000 °C and subsequently steaming at high pressure. Under low light intensity (193 W/m2), the light to vapor efficiency of maple WBM is more than 100%. The outstanding performance of WBM is attributed to (1) the facilitated water transport in the hierarchical, open-pore network preserved from the wood precursor in WBM and (2) the reduced evaporation enthalpy of confined water in WBM and the high broadband sunlight absorptivity of WBM. Moreover, the high evaporation rate causes the temperature of WBM to be lower than that of the surrounding water, enabling thermal energy harvesting by WBM from water and making a light-to-vapor efficiency of >100% feasible. This discovery offers opportunities for developing low-cost, high-performance water desalination or humidification devices deployable in remote areas with nonconcentrated natural sunlight.

3D printing of bio-inspired porous polymeric solar steam generators for efficient and sustainable desalination

Freshwater scarcity is a pressing issue worldwide, and solar steam generators (SSGs) have emerged as a promising device for seawater desalination, harnessing renewable solar energy to facilitate sustainable water evaporation. The facile fabrication approach for SSG with complex topologies to achieve high water evaporation efficiency remains a challenge. Herein, a MIL-101 (Fe)-derived C@Fe3O4 ink was employed to multi-jet fusion (MJF) printing of polymeric porous SSGs with specific topologies. The optimized porous structure endows the printed SSGs with capillary force, greatly promoting water transport. The tree-like topology enables high water evaporation rates under various simulated solar radiation conditions. A finite element model was built to fully understand the light-to-thermal energy conversion and water evaporation processes. Moreover, the MJF-printed SSGs exhibit self-cleaning properties and can automatically remove accumulated salt on their surfaces, enabling sustainable desalination. During prolonged testing, the water evaporation rate of the SSGs remained relatively stable and reached as high as 1.55 kg m−2 h−1. Additionally, the desalinated water met the standards for direct drinking water. This study presents a state-of-the-art technology for producing efficient SSGs for desalination and introduces a novel method for MJF printing of functional nanocomposites.

One-Step Electrochemically Prepared Bionic Hierarchical Nickel Black@Graphene Composite Membrane for Desalination by Solar-Thermal Energy Conversion.

Ingenious microstructure construction and appropriate composition selection are effective strategies for achieving enhanced performance of photothermal materials. Herein, a broccoli-like hierarchical nickel black@graphene (Ni@Gr) membrane for solar-driven desalination was prepared by a one-step electrochemical method, which was carried out simultaneously with the electrochemical exfoliation of graphene and the co-deposition of Ni@Gr material. The bionic hierarchical structure and the chemical composition of the Ni@Gr membrane increased the sunlight absorption (90.36%) by the light-trapping effect and the introduction of graphene. The Ni@Gr membrane achieved high evaporation rates of 2.05 and 1.16 kg m-2 h-1 under simulated (1 sun) and outdoor sunlight conditions, respectively. The superhydrophilicity and the hierarchical structure of the Ni@Gr membrane jointly reduced the evaporation enthalpy (1343.6 kJ/kg), which was beneficial to break the theoretical limit of the evaporation rate (1.47 kg m-2 h-1). This work encourages the application of bionic metal-carbon composite photothermal materials in solar water evaporation.

Thermo-adaptive interfacial solar evaporation enhanced by dynamic water gating

Solar-driven evaporation offers a sustainable solution for water purification, but efficiency losses due to heat dissipation and fouling limit its scalability. Herein, we present a bilayer-structured solar evaporator (SDWE) with dynamic fluidic flow mechanism, designed to ensure a thin water supply and self-cleaning capability. The porous polydopamine (PDA) layer on a nickel skeleton provides photothermal functionality and water microchannels, while the thermo-responsive sporopollenin layer on the bottom acts as a switchable water gate. Using confocal laser microscopy and micro-CT, we demonstrate that this unique structure ensures a steady supply of thin water layers, enhancing evaporation by minimizing latent heat at high temperatures. Additionally, the system initiates a self-cleaning process through bulk water convection when temperature drops due to salt accumulation, thus maintaining increased evaporation efficiency. Therefore, the optimized p-SDWE sample achieved a high evaporation rate of 3.58 kg m−2 h−1 using 93.9% solar energy from 1 sun irradiation, and produces 18–22 liters of purified water per square meter of SDWE per day from brine water. This dynamic water transport mechanism surpasses traditional day-night cycles, offering inherent thermal adaptability for continuous, high-efficiency evaporation.

Synthesis and characterization of hierarchical Ti3C2Tx MXene/graphitic-carbon nitride/activated carbon@luffa sponge composite for enhanced water desalination

In this study, advanced solar steam technologies are explored for their potential applications in seawater desalination and wastewater purification. We have developed a three-dimensional photothermal evaporator using MXene, luffa sponge (LS), graphitic-carbon nitride (GCN) and activated carbon (AC). The hierarchical Ti3C2Tx MXene/GCN/AC@LS composite photothermal evaporator exhibits superior thermostability, pH stability, and mechanical durability. The Ti3C2Tx MXene/GCN/AC@LS composite evaporator having a dimension of 1.25 cm displays excellent performance, leading to a high evaporation rate of 2.6 kg m−2h−1 and a high solar-thermal conversion efficiency of 96 % under 1 sun illumination. This high efficiency is attributed to the good light absorption by the Ti3C2Tx MXene/GCN/AC@LS composite coupled with a better wetting through the internal microchannels of the LS, which envisages a faster water delivery and evaporation of water. The Ti3C2Tx MXene/GCN/AC@LS composite captures the residual heat from the sidewall surface as an additional source of energy.

Facile dual-functionalization of PEN nanofibrous membranes with solar evaporation and photocatalysis for efficient dye wastewater purification

Purification of dye wastewater by combining photocatalytic degradation with solar energy-driven interfacial water evaporation has emerged as a promising approach to address water pollution in recent years. In this work, a high-performance polymer, polyarylene ether nitrile (PEN), was electrostatically spun to construct a robust nanofibrous substrate, then dual-functionalized using polyaniline (PANI) and titanium dioxide (TiO2) via a facile polydopamine (PDA)-assisted vacuum self-assembly method. Moreover, the CA of the PEN membrane after PDA and PANI@TiO2 treatment changes from 20° to 0° within 0.4 s, showing superhydrophilic properties and providing rapid water supply for water evaporation. PANI and TiO2 were employed as the photo-thermal conversion component and photocatalytic component, respectively. The fabricated dual-functionalized PANI@TiO2/PEN composite nanofibrous membrane exhibited a high water evaporation rate of up to 3.23 kg m−2 h−1 under a simulated solar illumination of 1 KW m−2. Owing to the reduction in the photoelectron-hole recombination rate promoted by PANI, the composite nanofibrous membrane demonstrated a favorable dye removal rate of 92.18% in 6 h for methylene blue (MB). Furthermore, the robust PEN nanofibrous skeleton conferred the composite membrane with thermal resistance and corrosion resistance properties, ensuring long-term performance in harsh environments. The facile fabricated PANI@TiO2/PEN membrane achieved comprehensive performance, offering a promising strategy by combining solar-driven interfacial water evaporation and photocatalytic degradation for water purification.

Design of MOF-Based Solar Evaporators with Hierarchical Microporous/Nanobridged/Nanogranular Structures for Rapid Interfacial Solar Evaporation and Fresh Water Collection.

Interfacial solar evaporation (ISE) holds considerable promise to solve fresh water shortage, but it is challenging to achieve high evaporation rate (Reva) and fresh water yield in close system. Here, we report design and preparation of MOF-based solar evaporators with hierarchical microporous/nanobridged/nanogranular structures for rapid ISE and fresh water collection in close system. The evaporators are fabricated by growing silicone nanofilaments with variable length as nanobridges on a microporous silicone sponge followed by grafting with polydopamine nanoparticles and Cu-MOF nanocrystals. Integration of the unique structure and excellent photothermal composites endows the evaporators with high Reva of 3.5-20 wt% brines (3.60-2.90 kg m-2 h-1 in open system and 2.38-1.44 kg m-2 h-1 in close system) under simulated 1 sun, high Reva under natural sunlight, excellent salt resistance and high fresh water yield, which surpass most state-of-the-art evaporators. Moreover, when combined with a superhydrophilic cover, the evaporators show much higher average Reva of real seawater, remarkable fresh water yield and excellent long-term stability over one month continuous ISE under natural sunlight. The findings here will promote the development of advanced evaporators via microstructure engineering and their real-world ISE applications.

Antibacterial Janus cellulose/MXene paper with exceptional salt rejection for sustainable and durable solar-driven desalination

The scarcity of freshwater resources and increasing demand for drinking water have driven the development of durable and sustainable desalination technologies. Although MXene composites have shown promise due to their excellent photothermal conversion and high thermal conductivity, their high hydrophilicity often leads to salt precipitation and low durability. In this study, we present a novel Cellulose (CF)/MXene paper with a Janus hydrophobic/hydrophilic configuration for long-term and efficient solar-driven desalination. The paper features a dual-layer structure, with the upper hydrophobic layer composed of CF/MXene paper exhibiting convexness to serve as a photothermal layer with exceptional salt rejection properties. Simultaneously, the bottom porous layer made of CF acts as an efficient thermal insulation. This unique design effectively minimizes heat loss and facilitates efficient water transportation. The Janus CF/MXene paper demonstrates a high evaporation rate of 1.11 kg m−2h−1 and solar thermal conversion efficiency of 82.52 % under 1 sun irradiation. Importantly, even after 2500 h of operation in a simulated seawater environment, the paper maintains a stable evaporation rate without significant salt deposition and biodegradation due to an antibacterial rate exceeding 90 %. These findings highlight the potential of the Janus CF/MXene paper for scalable manufacturing and practical applications in solar-driven desalination.

Glass capillary array supported membrane evaporator balancing heat and water management for double-side solar-driven interfacial evaporation

Efficient heat and water management are two important aspects for boosting solar-driven interfacial evaporation. Here, we develop a glass capillary array supported membrane evaporator (GCSE) to simultaneously achieve heat and water management. In the GCSE, a membrane at top regions enables photothermal conversion, and a glass capillary array at bottom regions serves as both water and heat management. The balance of heat and water management can be readily controlled by adjusting the number and height of glass capillary array. Moreover, the exposed bottom surface of GCSE further utilizes extra evaporation surface to boost evaporation. As a result, a high evaporation rate of 2.06 kg m−2 h−1 with an efficiency of 98.6% under 1 sun is achieved. Furthermore, the GCSE also exhibits potential applications in oil/water emulsion purification and seawater desalination.

High-performance Chinese ink flower-shaped evaporator: Intensified heat through light concentration to achieve water-energy balance

Maintaining a water-energy balance is crucial for maximizing efficiency in 3D interfacial solar-driven evaporation. Regrettably, the inherent flaw of 3D evaporators results in insufficient water supply capacity. Herein, taking inspiration from metals that can reflect light, aluminum foil (AF) was utilized to create a light-collecting device with internal reflection capabilities. A 3D sola flower (SF) evaporator with Chinese ink absorption coating and PDA surface hydrophilic treatment (IPSF) was designed. The experimental and simulated results show that by applying surface hydrophilic treatment and using a light-collecting device, a notable increase in temperature on the side of the 3D evaporator is visible, indicating the successful implementation of the spotlight effect. Therefore, it is possible to achieve a water-energy balance and attain a high evaporation rate. The evaporation rate of IPSF was 2.31 kg m−2 h−1 before concentrating light under one sun and 3.5 wt% brine. Comparably, it rose to 3.95 kg m−2 h−1 after concentrating (IPSFCL), marking a 71 % enhancement. This innovative light-collecting device and water-energy balance engineering provides a novel strategy and technique for designing 3D evaporators and can be applied in different environmental conditions.

Solar-driven salt-free deposition evaporation for simultaneous desalination and electricity generation based on tip-effect and siphon-effect

Solar-driven desalination is a promising way to alleviate the freshwater shortage, while is facing challenges posed by low evaporation rates and severe salt accumulation. Herein, a high-performance two-dimensional (2D) solar absorber with Co3O4 nanoneedle arrays (Co3O4-NN) grown on the surface of reduced graphene oxide-coated pyrolyzed silk cloth (Co3O4-NN/rGO/PSC) was prepared, and a salt-free evaporator system was assembled based on the composite material and siphonage-the flowing water delivery. It is revealed that the evaporation enthalpy of water can be reduced over the 2D solar absorber grown with Co3O4-NN, enabling an evaporation rate of up to 2.35 kg m−2 h−1 in DI water under one solar irradiation. The desalination process can be carried out continuously even with salt concentration up to 20 wt%, due to the timely removal of concentrated brine from the interface with the assistance of directed flowing water. Moreover, the 2D structure and the flowing water also provide an opportunity to convert waste solar heat into electricity in the evaporator based on the seebeck effect, ensuring simultaneous freshwater production and power generation. It is believed that this work provides insights into designing hybrid systems with high evaporation rate, salt resistance, and electricity generation.

Superhydrophilic hollow-copper sulfide/polyvinyl alcohol-coated waste masks upcycling for photothermal water evaporation

This study focused on transforming waste face masks into superhydrophilic hollow copper sulfide (CuS)/polyvinyl alcohol (PVA)-coated masks to significantly improve photothermal water evaporation, providing a novel approach to environmental sustainability and water scarcity challenges. The as-made hollow CuS nanoparticles were effectively coated on the fibers of waste masks and then treated with PVA to improve their hydrophilicity. This modification aimed to leverage solar energy for efficient water evaporation. Experimental results under different light irradiation conditions showed that the CuS/PVA-masks achieved a high water evaporation rate of 2.533 kg/m²h, which is a 1.82-fold increase over pure water and a remarkable improvement over untreated masks. By using cutoff filters that selectively allow certain wavelengths of a xenon lamp, it was found that the presence of ultraviolet (UV) light significantly increases the evaporation rate, whereas the exclusion of UV and visible light, leaving only infrared (IR) light, results in a lower efficiency. This research highlights the potential of repurposing waste masks as functional materials for solar-driven water evaporation applications such as water treatment and desalination.

Weather-related changes in the dehydration of respiratory droplets on surfaces bolster bacterial endurance

HypothesisThe study shows for the first time a fivefold difference in the survivability of the bacterium Pseudomonas Aeruginosa (PA) in a realistic respiratory fluid droplet on fomites undergoing drying at different environmental conditions. For instance, in 2023, the annual average outdoor relative humidity (RH) and temperature in London (UK) is 71 % and 11 °C, whereas in New Delhi (India), it is 45 % and 26 °C, showing that disease spread from fomites could have a demographic dependence. Respiratory fluid droplet ejections containing pathogens on inanimate surfaces are crucial in disease spread, especially in nosocomial settings. However, the interplay between evaporation dynamics, internal fluid flow and precipitation and their collective influence on the distribution and survivability of pathogens at different environmental conditions are less known. ExperimentsShadowgraphy imaging is employed to study evaporation, and optical microscopy imaging is used for precipitation dynamics. Micro-particle image velocimetry (MicroPIV) measurements reveal the internal flow dynamics. Confocal imaging of fluorescently labelled PA elucidates the bacterial distribution within the deposits. FindingsThe study finds that the evaporation rate is drastically impeded during drying at elevated solutal concentrations, particularly at high RH and low temperature conditions. MicroPIV shows reduced internal flow under high RH and low temperature (low evaporation rate) conditions. Evaporation rate influences crystal growth, with delayed efflorescence and extending crystallization times. PA forms denser peripheral arrangements under high evaporation rates and shows a fivefold increase in survivability under low evaporation rates. These findings highlight the critical impact of environmental conditions on pathogen persistence and disease spread from inanimate surfaces.

The Impact of Land Use on Water Resources in the Gulf Cooperation Council Region

The Gulf Cooperation Council (GCC) countries experience a harsh environment with low precipitation and high evaporation rates. This presents a significant challenge of water scarcity and water quality degradation which is exacerbated by land use practices. Agriculture, urbanization, and industrialization are impacting the management of water resources. This paper examines the state of water resources in the GCC countries and presents the impact of land use practices. A detailed analysis of the relationship between land use and groundwater is conducted with a focus on the Kingdom of Saudi Arabia (KSA), the Sultanate of Oman, and the United Arab Emirates (UAE). The results indicate a drop in agricultural activities, an increase in bare land and urban areas, depletion of groundwater, and water quality degradation. These changes were attributed to excessive agricultural and industrial uses, climate change, and rapid urbanization. The findings show the need for sustainable land use practices and water resources management. Further research addressing the impact of land use on water in Kuwait, Qatar, and Bahrain, and evaluating the effectiveness of policy, is essential.

MoS2 supported hydrophilic porous membrane for solar water evaporation

Solar powered interfacial water evaporation has become one of the most direct and sustainable technologies for seawater desalination. However, developing an efficient, stable evaporator with good salt resistance is a critical and challenging. In this work, MoS2-CNT@C membranes synthesized by loading 1T/2H MoS2 flower spheres on the CNT@C hierarchically porous membrane by hydrothermal method are used as solar water evaporators. MoS2-CNT@C membranes, as photothermal conversion materials, have broadband solar absorption capacity and good hydrophilicity. The porous structure of CNT@C membrane can provide great water transport channels, and the decoration of flower spheres MoS2 enhances the internal reflection which can increase the sunlight absorption capacity, resulting in a jump in water evaporation properties. The membrane has a high evaporation rate of 2.53 kg m−2h−1 under one sun illumination. In addition, the evaporation rate of the sample in seawater reaches 2.51 kg m−2h−1, similar to that in the pure water, and remains stable after several evaporation cycles, ensuring that high quality fresh water can be produced during the desalination.

Vertically aligned sheet-like structural aerogel incorporated with expanded graphite for efficient solar desalination and atmospheric water harvesting

Solar desalination and atmospheric water harvesting are economically friendly techniques for obtaining freshwater. However, developing aerogels capable of simultaneously achieving long-term stable operation of efficient solar desalination and atmospheric water harvesting remains challenging. The aramid fiber (AF)-reinforced vertically aligned sheet-like structural aerogel incorporated with expanded graphite was prepared through a sequential process involving freeze-drying, carbonization, and tannin surface modification. The aerogel can serve directly as a seawater desalination evaporator and function as an atmospheric water harvester through LiCl loading. The vertical sheet-like structure of the aerogel enables the evaporator to exhibit a high evaporation rate, reaching 2.4 kg m-2h-1 under 1 kW m-2 simulated solar radiation. The high specific surface area allows the aerogel to load a large amount of LiCl, resulting in a water absorption capacity as high as 3.29 g g-1 (90 % RH), and it can release 80 % of the adsorbed water within 120 min under only 0.5 kW m-2 simulated solar radiation. The laminar void structure of EG can restrict the movement of LiCl, preventing its leakage and ensuring stable water harvesting performance. The water evaporator and harvester both demonstrated excellent stability during cycling tests. Additionally, due to the reinforcing effect of AF, the compression strength of the aerogel reaches as high as 110.9 kPa. The prepared aerogel has promising prospects for freshwater acquisition.

Hofmeister Effect-Assisted Facile Fabrication of Self-Assembled Poly(Vinyl Alcohol)/Graphite Composite Sponge-Like Hydrogel for Solar Steam Generation.

The use of hydrogel-based interfacial solar evaporators for desalination is a green, sustainable, and extremely concerned freshwater acquisition strategy. However, developing evaporators that are easy to manufacture, cheap, and have excellent porous structures still remains a considerable challenge. This work proposes a novel strategy for preparing a self-assembling sponge-like poly(vinyl alcohol)/graphite composite hydrogel based on the Hofmeister effect for the first time. The sponge-like hydrogel interfacial solar evaporator (PGCNG) is successfully obtained after combining with graphite. The whole process is environmental-friendly and of low-carbon free of freezing process. The PGCNG can be conventionally dried and stored. PGCNG shows impressive water storage performance and water transmission capacity, excellent steam generation performance and salt resistance. PGCNG has a high evaporation rate of 3.5kg m-2 h-1 under 1kW m-2 h-1 solar irradiation and PGCNG demonstrates stable evaporation performance over both 10h of continuous brine evaporation and 30 cycles of brine evaporation. Its excellent performance and simple, scalable preparation strategy make it a valuable material for practical interface solar seawater desalination devices.

Polar bear hair inspired 3D photothermal evaporator for efficient solar steam desalination and electricity generation

While solar steam generation for desalination and electricity production is a burgeoning field, traditional systems often face challenges with rapid heat loss and salt buildup. To address these issues, we introduce a biomimetic approach, inspired by the unique thermal properties of polar bear hair. Our study presents a photothermal 3D hierarchical hollow Ppy@CuO nanorod array system, featuring a dual-structured design: a cone-shaped 3D topological structure for improved light absorption and a hollow structure for enhanced thermal insulation. This innovative approach effectively maximizes solar energy capture and reduces thermal losses, particularly in marine environments. Our system exhibits outstanding performance in solar steam generation, achieving high water evaporation rates and maintaining stability and efficiency in high-salinity settings. Under one solar illumination at a 75° tilt angle, the Ppy@CuO-3 NAs demonstrated an evaporation rate of 3.3 kg m−2 h−1 and an energy efficiency of 97.5 %. Additionally, the synergistic effect of released Cu2+ and Ppy resulted in a 99.9 % antibacterial rate against E. coli and S. aureus. This significant advancement in simultaneous, effective seawater desalination and efficient evaporation-driven electricity generation marks a crucial step toward future sustainable resource utilization.