Efficient Solar Evaporation Research Articles

Sustainable MXene/PDA hydrogel with core-shell structure tailored for highly efficient solar evaporation and long-term desalination

Solar evaporation is an effective means to solve the scarce of fresh water resources. The developed solar evaporator has the disadvantages of low evaporation rate, poor mechanical performance, difficulty in long-term evaporation, and insufficient water purification capacity. Herein, we have developed a core-shell structure hydrogel solar evaporator taking MXene/PDA as the photothermal material. The hydrogel matrix possesses self-healing and remoldability, which is sustainable and in line with the theme of current material development. The prepared core-shell structure hydrogel showed excellent properties, with a compressive stress of 0.4 MPa and the evaporation rate is as high as 3.02 kg m−2 h−1, and the evaporation efficiency is 94.7 % under 1 sun illumination, which is better than most of the previously reported solar evaporators. Through the durability experiment in simulated seawater, the long-term desalination ability was verified. Simultaneously, the solar evaporator also exhibits various functions such as dye resistance, and heavy metal ion resistance. The core-shell structure solar evaporator shows great potential in long-term seawater desalination and water purification. Furthermore, it provides a promising strategy for the structural design of solar evaporators in the future.

Achieving steam and electrical power from solar energy by MoS2-based composites

Photothermal conversion has hold great promise for facing water scarcity by solar evaporation technology. However, the photothermal performance of the evaporators is limited by weather rhythm due to strong dependence on solar energy. Herein, MoS2-based composites are well-suited for maximize resource utilization by achieving steam and electrical power from solar energy. Under one sun radiation, the output voltage can be up to ~ 300 mV synchronously with efficient solar evaporation. The power output is ~ 3.35 mW m−2 with current of 6.7 µA after half an hour of one sun illumination. The power output of ~ 0.9 mW m−2 can be readily derived with voltage of ~ 200 mV and current of 2.7 µA under ambient conditions. Furthermore, the voltage output reveals a linear increase behavior through the series connection of energy generators. MoS2-based composites show the potential of simultaneous steam and energy generation under sunlight, and it realizes the value as energy generators on cloudy days or at night. The work demonstrates that MoS2-based composites are capable of full-time function only relying on solar energy and water.

3D Photothermal Cryogels for Solar-Driven Desalination.

This paper reports the fabrication of photothermal cryogels for freshwater production via the solar-driven evaporation of seawater. Photothermal cryogels were prepared viain situ oxidative polymerization of pyrrole with ammonium persulfate on preformed poly(sodium acrylate) (PSA) cryogels. We found that the pyrrole concentration used in the fabrication process has a significant effect on the final PSA/PPy cryogels (PPCs), causing the as-formed polypyrrole (PPy) layer on the PPC to evolve from nanoparticles to lamellar sheets and to consolidated thin films. PPC fabricated using the lowest pyrrole concentration (i.e., PPC10) displays the best solar-evaporation efficiency compared to the other samples, which is further improved by switching the operative mode from floating to standing. Specifically, in the latter case, the apparent solar evaporation rate and solar-to-vapor conversion efficiency reach 1.41 kg m–2 h–1 and 96.9%, respectively, due to the contribution of evaporation from the exposed lateral surfaces. The distillate obtained from the condensed vapor, generated via solar evaporation of a synthetic seawater through PPC10, shows an at least 99.99% reduction of Na while all the other elements are reduced to a subppm level. We attribute the superior solar evaporation and desalination performance of PPC10 to its (i) higher photoabsorption efficiency, (ii) higher heat localization effect, (iii) open porous structure that facilitates vapor removal, (iv) rough pore surface that increases the surface area for light absorption and water evaporation, and (v) higher water-absorption capacity to ensure efficient water replenishment to the evaporative sites. It is anticipated that the gained know-how from this study would offer insightful guidelines to better designs of polymer-based 3D photothermal materials for solar evaporation as well as for other emerging solar-related applications.

Biomimetic surface strategy of spectrum-tailored liquid metal via blackbody inspiration for highly efficient solar steam generation, desalination, and electricity generation

Solar steam generation as a promising strategy has attracted more and more attention owing to its applications of the water purification which meet the demand of clean water worldwide. Photothermal material, as the key component of solar evaporators, has aroused great interest in the design of extraordinary photothermal conversion efficiency. Herein, liquid metal was the first time used to develop a photothermal promotor with the tailored spectrum via the dipole layer strategy for highly efficient solar steam generation. As the proof-of-concept, cellulose nanocrystals were applied as bonding agent of matrix scaffold and photothermal layer for the successful preparation of the lignin-based aerogel evaporators. Inspired by the seedless sunflower, binary configurations of interior topology and surface topography was manipulated on the layer-doubled lignin-based aerogels with inverted pyramid veneer for the favorable multi-functionalities, which could hardly realize within the entirety before. The blackbody-inspired aerogel evaporators showed exceptional solar evaporation efficiency of 94% under 1 sun, and the depuration and desalination efficiency up to 99% in the sewage (water containing Zn2+, Ni2+, Cu2+, Fe3+) and seawater (Yellow sea, China). In addition, the resulted lignin-based aerogels also presented a promising application in the electricity generation field. This work opens a new avenue to design liquid metals with excellent light absorption ability for the effective solar steam generation, sewage depuration and desalination, with the application of liquid metals in the electricity generation field.

Two Birds One Stone: Facile and Controllable Synthesis of the Ag Quantum Dots/Reduced Graphene Oxide Composite with Significantly Improved Solar Evaporation Efficiency and Bactericidal Performance.

Interfacial solar evaporation (ISE) is an environmentally friendly and promising water treatment strategy. However, the bactericidal performance of an ISE system during the evaporation process is usually ignored, which may result in potential water safety hazards. In this study, a facile method is presented for the controllable synthesis of Ag quantum dots (QDs)/rGO to simultaneously achieve efficient solar evaporation and evaporated water disinfection. The size of the Ag nanoparticles (NPs) rather than the loading amount is the factor that considerably affects the solar evaporation efficiency and the bactericidal performance. Under 1 sun of irradiation (1 kW·m2), the evaporation rate and solar evaporation efficiency of Ag QDs/rGO are as high as 2.11 kg·m2·h-1 and 94.0%, respectively. Based on E. coli and S. aureus, the bactericidal activity of Ag QDs/rGO in the evaporation process is qualitatively and quantitatively characterized; no bacteria could be detected in the evaporated water. Furthermore, various water samples, including acidic water, alkaline water, dye water, and seawater, are selected to verify the solar evaporation performance of Ag QDs/rGO. When considering complex water samples, the as-prepared material maintains a high evaporation efficiency and an excellent purification effect, indicating attractive potential for various practical applications.

Boron nanosheets loaded with MoS2 porous sponges for water purification

Utilizing solar steam generation to treat seawater and sewage, as an emerging and effective technology, can obtain clean water. There is an abundance of water demand and a shortage of water supply in the world today. Herein, we demonstrate an integrated evaporator of boron nanosheets modified with molybdenum disulfide (MoS2) as a photothermal materials and a konjac glucomannan (KGM) sponge with excellent pore structure as a thermal insulator and water supplier for solar clean water generation. A rapid evaporation rate (1.538 kg m−2 h-1) and high solar evaporation efficiency (96.5 %) under 1-sun radiation (1 kW m−2) can be achieved in the two-dimensional structure system. This work provides a new way to design and manufacture renewable solar steam generation for water purification.

Carbon monoliths from PET wastes for interfacial solar evaporation

Solar water evaporation systems based on carbon are emerging technologies for water desalination. In this work, carbon monoliths were obtained from polyethylene terephthalate (PET) wastes. Two different carbon monolith samples were obtained by varying the carbonization parameters. The carbon monoliths have a high solar absorptance due to its porous structure and offers a vapor transport, which facilitate a fast evaporation. The carbon monoliths had different thickness, those ones with 8 mm in thickness presented an enhanced water evaporation rate of 0.99 kg/m2h with a solar evaporation efficiency of 63.5%. Here we show that carbon monoliths obtained from PET wastes are promising materials for interfacial solar evaporation systems.

Carbon nanomaterials treated by combination of oxidation and flash for highly efficient solar water evaporation

The high-efficiency solar evaporation is a potential technique to desalinate hypersaline wastewater and seawater to alleviate the global fresh water shortage. Photo-thermal agent and solar evaporator with low-cost raw materials, high photo-thermal conversion efficiency and simple-fast preparation methods is crucial to realize the industrial application of solar evaporation. Herein, carbon nanomaterial with higher light absorption and photo-thermal conversion efficiency than that of carbon black was obtained by combination treatment of carbon black with oxidation and flash illumination. In order to characterize the evaporation performance of the devices, a floating evaporator was fabricated with the carbon nanomaterial on the top of polyethylene foam wrapped with non-woven fabrics. The evaporation rate and photo-thermal conversion efficiency of evaporators were affected significantly by environmental temperature and humidity. At the environmental temperature of 19.5 °C, the evaporator fabricated with the combined treated carbon nanomaterial as photo-thermal agents presents a stable evaporation rate at 1.27 kg m−2 h−1 and solar evaporation efficiency at 78.7% under 1 kW m−2 simulated sun illumination, which are higher than those of evaporator with carbon black (1.13 kg m−2 h−1 and 68.1%). The distilled water obtained from the solar evaporator met the standards of drinkable water. Overall, the experimental result demonstrates a great promise application of treated carbon nanomaterial as a photo-thermal agent in the field of seawater desalination and solar-energy collector.

Solar Driven Interfacial Steam Generation Derived from Biodegradable Luffa Sponge

AbstractA chemically treated luffa sponge (LS) derived from the ripe fruit of the Luffa cylindrica (LC) plant is investigated as an efficient solar photothermal conversion material for water purification applications for the very first time. Hydrophilicity and solar absorbance of the LS are enhanced by dopamine treatment and candle soot surface coating. The fabricated surface modified LS (SM‐LS) leads to a superb solar evaporation rate of water as high as 1.30 kg m−2 h−1, which is five times higher than that of the freshwater under 1 sun illumination. The outdoor experiment shows an excellent solar evaporation efficiency of 79.98%, which is significantly higher than other low‐cost materials. Such SM‐LS can be further applied to desalinate seawater, where it is shown that 1 m2 of surface‐modified LS can produce 7.5–8 L of freshwater per day. Hence, the proposed system can be utilized in remote areas and refugee camps.

Sustainable self-cleaning evaporator for long-term solar desalination using gradient structure tailored hydrogel

Interfacial solar evaporation has been demonstrated as a promising strategy to mitigate water scarcity. However, for practical application in marine environment, the accumulation of salt and growth of microorganisms such as bacteria will cause scarring and fouling of the evaporators, depressing the potential for long-term sustainable use. Here, we report a hydrogel evaporator (chitosan/PAAm/PPy) with integrated three-layer structure containing individual functions for heat localization to improve solar evaporation efficiency, salt redissolution and antibacterial growth for sustainable long-term use, as well as management of thermal energy loss, respectively. The as-fabricated hydrogel evaporator presented a high-water evaporation rate of 2.41 kg m-2h−1 under 1-sun illumination, and excellent self-cleaning property against the salt accumulation and bacteria growth. During a two-week continuous evaporation experiment in simulated marine water with 3.5 wt% salinity and mixture of bacteria, the evaporator generated vapor stably in a range of 2.30 ~ 2.41 kg m-2h−1, without noticeable performance decay. Additionally, the hydrogel evaporator shows a stable vapor generation rate during cycled dehydration-hydration processes, as well as against repeated weight loading–unloading tests, indicating its convenience for long-term use and storage.

Polyacid doping-enabled efficient solar evaporation of polypyrrole hydrogel

Solar evaporation opens opportunities for solving the problem of global water scarcity. Polypyrrole (PPY) hydrogels are promising materials for solar steam generation, however, the improvement of steam generation ability remains a challenge. In this paper, we developed a “polyacid doping” strategy by introducing butane tetracarboxylic acid (BTA) to synthesize a novel BTA-doped PPY hydrogel referred to as PPY/BTA hydrogel, that is cross-linked by PPY ligaments with diameters of ~200 nm. Due to the successful doping with hydrophilic BTA, PPY/BTA hydrogel exhibits an enhanced solar energy conversion efficiency (ƞ = 89%) under simulated sunlight (1 kW m−2). Additionally, the evaporation rate (V) of water can reach 1.90 kg m−2 h−1 which is 1.55 times higher than the value (1.22 kg m−2 h−1) obtained using a common PPY product without BTA. This is the most prominent among the reported PPY hydrogels under 1 sun irradiation. Moreover, efficient solar evaporation is found in regenerating wastewater containing Ag nanoparticles and dye, as well as seawater desalination, displaying wide applications. The synthesis method represents a rational design of a high-performance PPY hydrogel for solar evaporation, and could also shed light on fabricating conducting polymer networks for other applications.

Forest waste to clean water: natural leaf-guar-derived solar desalinator.

Water scarcity and waste mismanagement are global crises that threaten the health of populations worldwide and a sustainable future. In order to help mitigate both these issues, a solar desalination device composed entirely of fallen leaves and guar - both natural materials - has been developed and demonstrated herein. This sustainable desalinator realizes an evaporation rate of 2.53 kg m-2 h-1 under 1 sun irradiance, and achieves consistent performance over an extended exposure period. Furthermore, it functions efficiently under a variety of solar intensities and in high salinity environments, and can produce water at salinities well within the acceptable levels for human consumption. Such strong performance in a large variety of environmental conditions is made possible by its excellent solar absorption, superb and rapid water absorption, low thermal conductivity, and considerable salt rejection abilities. Composed primarily of biowaste material and boasting a simple fabrication process, this leaf-guar desalinator provides a low-cost and sustainable avenue for alleviating water scarcity and supporting a green path forward.

Recent advances and rational design strategies of carbon dots towards highly efficient solar evaporation.

Solar evaporation using photothermal materials is an environmentally friendly and feasible solution to overcome the water scarcity issue by utilizing the abundant solar energy source. Some key points for efficient solar-to-thermal energy conversion have been extensively studied. Among them, the advancement of solar absorber materials has emerged as an attractive research topic, owing to their potential to enhance the efficiency of solar to thermal conversion significantly. Recently, carbon dots (CDs) have attracted great interest for their applications in this field. CDs have many desirable properties, such as broad light absorption (200-800 nm), high photothermal conversion efficiency (more than 90%), tunable structure and surface functionalization, easy to produce and abundant raw materials that meet the requirements for this application. In this review, the integration of CDs into solar evaporation systems and recent advances in CD-based solar absorbers will be summarized and discussed. Before that, brief knowledge of carbon-based solar thermal evaporation, including its mechanism and strategies to improve the efficiency, is provided, followed by CDs' synthesis and tunable properties that can be optimized for this application. Finally, the challenges and perspectives of research for CD-based solar evaporation are proposed, for example, optimizing solar absorbers by decorating hydroxyl-rich CDs in 2D or 3D structures.

Solar Evaporation: Bioinspired Fractal Design of Waste Biomass‐Derived Solar–Thermal Materials for Highly Efficient Solar Evaporation (Adv. Funct. Mater. 3/2021)

Solar Evaporation: Bioinspired Fractal Design of Waste Biomass‐Derived Solar–Thermal Materials for Highly Efficient Solar Evaporation (Adv. Funct. Mater. 3/2021)

Evaporation efficiency monitoring device based on biomass photothermal material for salt-resistant solar-driven interfacial evaporation

Solar-driven interface evaporation has received much attention due to its high-efficiency photothermal conversion efficiency. However, in practical application, it is difficult to monitor whether the evaporation efficiency of photothermal conversion materials can maintain high efficiency and stability for a long time. In this paper, taking surface modified coconut fiber (SCF) as photothermal material, we designed a set of evaporation efficiency monitoring device (EEMD) and demonstrated the strategy of building a solar evaporation efficiency monitoring system. The SCF shows superhydrophilic wettability, and its vertical multi-stage open-framework structure is benefit to the rapid transport of water. Under 1 kW m−2 illumination, evaporation rate of SCF is 1.5 kg m−2 h−1, evaporation efficiency is 90.2%. In 20% NaCl, evaporation rate of SCF is 1.37 kg m−2 h−1, and energy conversion efficiency is 85.3%. In order to monitor the stability of evaporator efficiency, we designed a simple EEMD which applied platinum wire electrode to monitor the change of electric potential in the evaporator. The results show that the electric potential is positively correlated with the evaporation efficiency. EEMD provides a new monitoring method for the efficient and stable operation of solar evaporator.

Continuous solar desalination based on restricted salt crystallization zone

Salt crystallization is a key factor restricting the long-term application of solar desalination. In this study, a new type of solar evaporator with loose lateral channels was successfully prepared to control the salt crystallization phenomenon during solar evaporation process. The evaporation rate and solar evaporation efficiency of the prepared evaporator increased to 1.32 kg/m2 h and 88%, respectively. The evaporation rate was maintained above 1.2 kg/m2 h when the high concentration brine was used for evaporation treatment for a long time, and the salt crystallization zone was limited to the edge of the photothermal layer. The re-dissolved polyethylene glycol (PEG) constructed the smooth lateral channels for salt solution transport in the graphene oxide (GO) photothermal layer, and the concentrated salt solution was more likely to be transported laterally to the edge of GO layer due to the resistance of upward transport during solar evaporation. Because the formation area of crystalline salt was limited to the edge of the photothermal layer, the effective evaporation area of the photothermal layer was maintained, thereby ensuring continuous solar desalination.

Polymeric Membranes with Selective Solution-Diffusion for Intercepting Volatile Organic Compounds during Solar-Driven Water Remediation.

Solar evaporation through a photothermal porous material provides a feasible and sustainable method for water remediation. Several photothermal materials have been developed to enhance solar evaporation efficiency. However, a critical limitation of current photothermal materials is their inability to separate water from the volatile organic compounds (VOCs) present in wastewater. Here, a microstructured ultrathin polymeric membrane that enables freshwater separation from VOC pollutants by solar evaporation with a VOC removal rate of 90%, is reported. The different solution-diffusion behaviors of water and VOCs with polymeric membranes facilitate their separation. Moreover, owing to increased light absorption, enlarged liquid-air interface, and shortened mass transfer distance, the microstructured and ultrathin configuration of the membrane helps to balance the tradeoff between permeation selectivity and water production capacity. The membrane is not only effective for evaporation of simulated volatile pollutants in a prototype, but can also intercept complex volatile organic contaminants in natural water sources and produce water that meets drinking-water standards. With practical demonstration and satisfactory purification performance, this work paves the way for practical application of solar evaporation for effective water remediation.

Bioinspired Fractal Design of Waste Biomass‐Derived Solar–Thermal Materials for Highly Efficient Solar Evaporation

AbstractSolar evaporation is considered a promising technology to address the issue of fresh water scarcity. Although many efforts have been directed towards increasing the solar–thermal conversion efficiency, there remain challenges to develop efficient and cost‐effective solar–thermal materials from readily available raw materials. Furthermore, further structural modification of the original biomass structure, particularly at multiple length scales, are seldom reported, which may further improve the solar–thermal performance of these material systems. Herein, a novel low‐cost system is developed based on a common bio‐waste, pomelo peels (PPs), through a bioinspired fractal structural design strategy, fractal carbonized pomelo peels (FCPP). This FCPP system shows an extremely high solar spectrum absorption of ≈98%, and marvelous evaporation rate of 1.95 kg m−2 h−1 with a solar–thermal efficiency of 92.4%. In addition, the mechanisms of the evaporation enhancement by fractal structural design are identified by numerical and experimental methods. Moreover, using FCPP in solar desalination shows great superiority in terms of cost and its potential in sewage treatment is also studied. The present work is an insightful attempt on providing a novel proposal to develop bio‐waste‐derived solar–thermal materials and construct biomimetic structures for efficient solar evaporation and applications.

Highly efficient solar water evaporation of TiO2@TiN hyperbranched nanowires-carbonized wood hierarchical photothermal conversion material

Solar water evaporation is a significant technique for water purification, desalination, and distillation. The approaches to obtain low-cost, low toxic and reusable material with high solar water evaporation efficiency are essential to solve the problem of drinking water shortage. Herein, we first synthesize TiO2@TiN hyperbranched nanowires on carbonized wood (CW) for solar water evaporation with a high solar water evaporation rate of 1.5252 kg m−2 h−1 and a solar thermal conversion efficiency about 94.01% under 1 kW m−2 simulated solar irradiation. The outstanding solar water evaporation performance can be contributed to the unique design of combining TiO2@TiN hyperbranched nanowires with CW. TiO2@TiN hyperbranched nanowires have better solar light absorption and higher specific area to evaporate water than TiN nanoparticles and nanotubes. At the same time, the evaporation enthalpy of water in the hyperbranched nanowires deceases obviously compared with that of normal bulk water. Besides, the hierarchical material possesses good stability and high solar evaporation efficiency both in seawater and in deionized water.

Dual-functional CuO/CN for highly efficient solar evaporation and water purification

Sunlight-clean water production from industrial wastewater, domestic sewage, and seawater is a sustainable water purification technology with the potential to solve environmental and energy problems. Semiconductor has good application prospects for photothermal conversion due to its advantages of earth-abundance, nontoxicity, and stability. While, most of its energy is released in the form of radiative relaxation, which leads to a low light-to-heat conversion efficiency. Enhancing its non-radiative relaxation is an effective way to improve light-to-heat conversion efficiency. In this work, heterostructured copper oxide/carbon nitride (CuO/CN) was designed to enhance non-radiative relaxation and thus improve the solar energy-to-thermal energy performance by constructing heterogeneous electric field. Electron paramagnetic resonance spectroscopy, X-ray photoelectron spectroscopy and differential charge density analyses proved the formation of heterogeneous electric fields between CuO and CN. Under the enhanced non-radiative relaxation, CuO/CN has an excellent light absorption range and carrier separation efficiency. The water evaporation rate under sunlight increased from 0.31 to 1.14 kg·m−2·h−1 and photothermal conversion efficiency increased from 19% to 72%. Simultaneously, CuO/CN can remove nearly 100% of the ions in seawater and Chemical Oxygen Demand (COD), Ammonia Nitrogen (NH3-N), Nitrate Nitrogen (NO3-N), and Total Phosphorus (TP) in industrial wastewater to produce clean water. Combined with photo-Fenton-like technology, it can effectively remove organic pollutants and volatile organic compounds (VOCs) from water. This work provides an efficient solar-clean water production technology with excellent pollution decontamination ability, which will be extremely attractive for future life.