Solar-driven Steam Generation Research Articles

Advanced bionic inverted coral solar evaporator: Enhancing sustainable water utilization with efficient and salt-resistant evaporation

Interfacial solar-driven steam generation technology shows great potential in addressing desalination and wastewater purification. However, there is a lack of advanced evaporators with high evaporation efficiency and salt tolerance, which is an obstacle to its widespread application. Drawing inspiration from marine coral structures, we develop a bionic inverted coral-type 3D solar evaporator with an array structure using structural engineering design. The microscopically porous vertical channel structure within the overall skeleton enhances the longitudinal reflux of salt ions and water evaporation, while macroscopic gaps in the bionic coral branching facilitate lateral advection–diffusion of salt ions. Numerical simulations confirm that this bionic coral structure design improves the diffusion rate of concentrated brine. Due to the localized surface plasma resonance and the Marangoni effect, the evaporator achieves remarkable water evaporation performance (evaporation rate: 2.72 kg m−2h−1, energy efficiency: 95.8 %) and operates reliably even under 20 % brine concentration (evaporation rate: 2.65 kg m−2h−1) without significant salt crystallization. Furthermore, it exhibits good wettability and robust mechanical properties, capable of withstanding a wide range of temperatures. The efficient and salt-resistant evaporation makes it valuable for applications including desalination, various wastewater treatments, and agricultural irrigation, thereby promoting the sustainable utilization of water resources.

Enhanced solar-driven steam generation and water purification using 3D arch solar evaporators

Steam generation strategy through solar-driven evaporators has now been widely recognized as one of the effective means to relieve the global fresh water crisis. Reducing heat loss has shown to be an effective way to improve the evaporation efficiency which has been overlooked in three-dimensional (3D) evaporators in the past. Herein, a superhydrophilic photothermal fabric was developed by the layer-by-layer assembly of carbon nanotubes followed by dip-coating with polyvinyl alcohol. The as-obtained photothermal fabric was designed as a 3D arch solar evaporator (ASE). The arch structure allowed the photothermal fabric to achieve double-sided water evaporation and a well-balanced saline water supply by controlling the height of the ASE. The ASE effectively captured the incident sunlight and demonstrated extraordinary thermal management performance, resulting in a saline water evaporation flux of 1.015–3.400 kg m−2 h−1 under 1 sun irradiation for 6 h. In addition, the proposed ASE exhibited excellent water purification for high salinity saline water, colored wastewater, and heavy metal wastewater. This work provides new insights into emerging solar steam generation systems by regulating the saline water supply balance.

Biomimic Design of Solar Steam Generation Devices Enabled by the Tannin-Iron Complex.

Solar-powered steam generation equipment has experienced considerable advancement in recent years as it offers a cleaner and greener method for freshwater production. However, the devices always suffer from a complicated process, high cost, and salt accumulation, which hinder their further application. Here, inspired by the water lily, a highly efficient and antisalt accumulation interfacial solar-driven steam generation device was designed by using the tannic acid-Fe3+ complex as photothermal material. The designed evaporator could be quickly unfolded within 24 s after being irradiated with light and then produce fresh water. It folded within 10 s and then sank into water for removing the accumulated salt after removing the irradiation sources. In addition, the tannic acid-Fe3+ complex on the evaporator surface and the angle of the evaporator allowed light to be reflected several times within the evaporator, effectively increasing the solar energy conversion efficient (2.22 kg/(m2·h)), and apparently, the overall evaporation efficiency of 139.18% was achieved under 1 sun illumination. Moreover, it exhibited an extraordinary antisalt accumulation capacity (by working continuously for 7 days in 10 wt % saline water and 80% reduction in salt accumulation) as well as a low price ($ 1.11/m2). This design would provide a strategy to prepare an antisalt accumulation solar steam devices.

Manipulating 2D Membrane Interlayer Channels with Accelerated Mass-Transfer Behavior to Boost Solar Desalination.

The scarcity of fresh water necessitates sustainable and efficient water desalination strategies. Solar-driven steam generation (SSG), which employs solar energy for water evaporation, has emerged as a promising approach. Graphene oxide (GO)-based membranes possess advantages like capillary action and Marangoni effect, but their stacking defects and dead zones of flexible flakes hinders efficient water transportation, thus the evaporation rate lag behind unobstructed-porous 3D evaporators. Therefore, fundamental mass-transfer approach for optimizing SSG evaporators offers new horizons. Herein, a universal multi-force-fields-based method is presented to regularize membrane channels, which can mechanically eliminate inherent interlayer stackings and defects. Both characterization and simulation demonstrate the effectiveness of this approach across different scales and explain the intrinsic mechanism of mass-transfer enhancement. When combined with a structurally optimized substrate, the 4Laponite@GO-1 achieves evaporation rate of 2.782kg m-2 h-1 with 94.48% evaporation efficiency, which is comparable with most 3D evaporators. Moreover, the optimized membrane exhibits excellent cycling stability (10 days) and tolerance to extreme conditions (pH 1-14, salinity 1%-15%), verifies the robust structural stability of regularized channels. This optimization strategy provides simple but efficient way to enhance the SSG performance of GO-based membranes, facilitating their extensive application in sustainable water purification technologies.

Remote-controlled saline tolerant tough-yet-strong solar vapor evaporator based on multifunctional Fe3O4 nanoparticles reinforced gel-nacre

Solar vapor evaporators in saline hold enormous potentials in resource sustainability, seawater desalination, as well as renewable energy harvesting. Nanocomposite hydrogels with the property of photothermal conversion have emerged as candidates for solar-driven steam generation devices, but are limited by remote control and low mechanical properties in a saline environment. Here, we developed a remote-controlled, saline tolerant, and tough-yet-strong solar vapor evaporator based on multifunctional Fe3O4 nanoparticles reinforced gel-nacre. The Fe3O4 nanoparticles play triple roles of acting as nano-crosslinks, photothermal converters, and untethered manipulation, coupling gel-nacre matrix with a shrinking tendency in saline that contributes to synergistic mechanical reinforcement. Such integrated magnetic nanocomposite hydrogel exhibits tough-yet-strong mechanical properties (19.58 MPa ultimate strength, 300 % failure strain, self-recoverability under 500 %, and fatigue-resistance), addressing the challenges of remote operation system and high strength requirement for practical applications. Moreover, good photothermal conversion performances (1.26 kg m−2 h−1 evaporation rate and 92.84 % evaporation efficiency) could be achieved with remotely controlled motion or adjustable position simultaneously under an external magnetic field. The intelligent solar vapor evaporation system based on multifunctional magnetic Fe3O4@gel-nacre nanocomposite provides new opportunities for flexible energy-transducing devices with untethered manipulation in saline environment.

SiO2@MXene-based fabric featuring low heat loss for high-efficiency solar-driven freshwater production

Interfacial solar-driven steam generation is a promising approach for addressing the global freshwater crisis. However, the lower evaporation rate owing to high heat-loss is still a primary obstacle to commercialization. Given the high transmittance to solar radiation and superior isolation to thermal radiation of SiO2 aerogel, herein we design a hanging SiO2@MXene-based fabric (SMF) evaporator for high-efficiency solar-driven freshwater production. Under light irradiation, the internal MXene-based fabric with high solar absorption can rapidly convert solar radiation into heat-energy, while the outermost transparent SiO2 aerogel with excellent thermal insulation performance can efficiently prevent the internal heat-quantity from escaping outward. As such, the solar-to-thermal is well confined within the MXene-based fabric, endowing SMF with low heat loss towards surroundings. An evaporation rate as high as 1.87 kg•m−2•h−1 along with heat-loss as low as 5.9% is achieved under 1-sun, superior to other prior evaporators. Better yet, neither a decrease in evaporation rate nor fouling on SMF is observed even when treating high-salinity brine. This work provides new insights into reducing heat loss to enhance evaporation rate during solar desalination.

A Sandwich Structure Ag/MgFe2O4-Deposited Surface Carbonized Wood for Integrated Solar Steam Generation and Photoreduction of Cr(VI).

The severe deterioration of the marine ecosystem significantly negatively impacts the performance of solar-driven steam generation (SSG) and the quality of the obtained freshwater. Herein, a bifunctional Ag/MgFe2O4@SCW reactor with a sandwich structure is designed for efficient SSG and Cr(VI) reduction, which is constructed via in situ deposit Ag nanoparticles (NPs) and MgFe2O4 onto surface carbonized wood (SCW). Owing to the advanced sandwich structure and strong interfacial interactions between each component, an ultra-high evaporation rate of 1.55kg m-2 h-1 and the efficiency of 88.6% are achieved using Ag/MgFe2O4@SCW under 1 sun. The system exhibits the long-term evaporation performance in the simulated sewage and strong acid/base solutions along with water-harvesting capacity in outdoor solar desalination. The quality of distilled water after desalination of actual seawater and NaCl solutions with different concentrations meets the WHO-recommended drinkable water standards. Furthermore, Ag/MgFe2O4@SCW shows outstanding antibacterial property, self-desalting capacity, as well as reusability and structure stability. Most importantly, the fast carrier separation endows Ag/MgFe2O4@SCW with superior photocatalytic activity and Cr(VI) photoreduction of up to 96.1% after 180min of illumination. The bifunctional Ag/MgFe2O4@SCW reactor provides an advanced synergistic mechanism for improving SSG and photocatalytic performance, while being promising for solar-powered production of clean water.

3D inverted cone hydrogels derived by MXene-TiOX nanocomposite for sequential regulation of enhanced solar-driven steam generation

Solar-driven steam generation technology is an environmentally friendly, cost-effective means of sewage treatment and seawater desalination. A significant challenge in the development of this technology is improving the evaporation performance of evaporation devices. Herein, we report an innovative three-dimensional (3D) solar evaporator constructed with MXene-TiOX nanocomposite as the photothermal layer and polyvinyl alcohol hydrogel as the water-transport medium. An inverted cone-concave structure of 30° on the photothermal layer can absorb more sunlight through diffuse light reflection. The 3D solar evaporator demonstrates a notable evaporation rate of 2.09 kg m⁻² h⁻¹ , surpassing the efficacy of alternative evaporative systems. In the seawater desalination experiment, the condensed water had salinity levels that were considerably lower than the established threshold for drinking water. The ion rejection ratios for the four primary ions demonstrate a high level of efficacy, with values approaching 99.91%. In addition, the 3D solar evaporator exhibits robust performance in the context of wastewater treatment. This study provides significant contributions to the understanding of the efficiency of solar evaporators based on structural design principles, offering approaches to mitigate the challenges posed by limited freshwater availability.

Efficient solar-driven steam generation for clean water production using a low-cost and scalable natural rubber composite sponge

Utilizing well-established foam production technology facilitates the scalability of the methodology described in this study, allowing SSG materials to rapidly transition from the laboratory to commercial and real-world applications.

Functional upcycling of waste polyester into Cr-MOF towards synergistic interfacial solar evaporation and organic pollutant degradation

The development of hybrid photothermal materials coupling interfacial solar-driven water evaporation with advanced oxidation process has recently aroused extensive attention to simultaneously realize freshwater production and wastewater purification. However, designing advanced hybrid photothermal materials with high specific surface areas and robust active sites remains challenging to meet the distinct requirements of photothermal conversion and photocatalysis. Herein, we report the waste-to-metal-organic framework (MOF) strategy for converting waste poly(ethylene terephthalate) [PET] into Cr-MOF hexahedron with abundant active sites and large specific surface area (896.1 m2/g), and subsequently fabricate multifunctional chromium-based metal-organic frameworks (Cr-MOF)/carbon nanotube (CNT) composite solar evaporators in a cost-effective, scalable manner towards simultaneous interfacial solar-driven steam generation and stubborn contaminant removal. First, the composite evaporator presents high light absorption (98%), high photothermal conversion efficiency, super-hydrophilicity, low thermal coefficient (0.087 W/(m/K)) and low vaporization enthalpy. Accordingly, the composite evaporator not only holds a high evaporation rate (2.46 kg/(m2/h)), superior to most of advanced solar evaporators, but also owns good flexibility and long-term stability. Subsequently, according to density functional theory (DFT) calculation and COMSOL results, chromium sites of Cr-MOF and local solar heat contribute to the peroxymonosulfate (PMS) activation to produce various reactive species. Thereupon, the composite evaporator exhibits good tetracycline (TC) degradation activity. Finally, in the practical freshwater production and photocatalytic degradation, the freshwater production amount is 7.3 kg/m2 per day, along with the tetracycline degradation efficiency of 92.4%. This work provides an ingenious strategy to massively synthesize hybrid evaporators and concurrently advances freshwater production and pollutant elimination.

Exploring perovskite oxide for advancing salt-resistant photothermal membranes and reliable thermoelectric generators

Solar-driven water purification is a promising technology that efficiently exploits solar energy for water purification, desalination, and energy generation. However, poor material compliance requires intensive energy to generate vapors under natural sunlight with real-time practical implications. Therefore, advanced functional nanomaterials are highly desirable for reducing energy demand for water evaporation. Herein, we report bifunctional La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) perovskite oxide for solar-driven steam and thermoelectric generation. The hydrophilic/hydrophobic structure endows excellent salt-rejection, thermal management, and hydrophilic water channels for an efficient solar evaporation rate (2.36 kg m−2 h−1) using seawater (3.5 wt%) under 1 kW m−2 irradiation. More importantly, the salt-resistant and thermally insulated evaporation structure drives brine through milli-drilled water channels and re-dissolves back into the water body without impeding evaporation efficiency (16.83 kg m−2 mass change during 8 h under 1 sun irradiation). Besides, the LSCF-based photo-thermoelectric generator harvests solar energy into an electric output (Vout ∼ 292.2 mV, and Iout ∼ 52.5 mA). The state-of-the-art investigations and heat transfer simulations portray the device's functionality and its optimization toward long-term durability, thermoelectricity, and a suitable option for remote sensing areas.

Banana pseudostem-inspired fluidic photothermal structure towards efficient solar steam generation and continuous salt rejecting

Solar-driven steam generation (SSG) is emerging as a promising off-grid strategy to relieve freshwater shortage. In recent years, extensive research works have been conducted to develop full biomass-based SSGs due to their unique hierarchical structural features. However, the long-term durability of biomass-based SSGs remains a concern. Herein, the discarded banana pseudostems have been demonstrated as an excellent potential SSG through a simple surface flame treatment. Firstly, the well-developed pore structure, superior light absorbance, extremely low thermal conductivity and superhydrophilic properties of the surface carbonized banana pseudostem (SCBP) have been well revealed respectively. In addition, it is also demonstrated that the SCBP evaporator can achieve an impressive evaporation rate of up to 2.548 kg·m−2·h−1 with a 91.96 % solar-thermal conversion efficiency superior to most reported biomass based SSGs. Furthermore, a SCBP inspired one-way fluidic photothermal structure is dedicatedly constructed. It is found that the salinity on the top surface of the SCBP evaporator remains far below 26 wt% and the evaporation rate is maintained at 2.384 kg·m−2·h−1 in a 15 wt% NaCl solution even after 200 h. Finally, from a proof-of-concept demonstration, the SCBP evaporator also shows an excellent water purification and seawater desalination performance in a real ocean situation.

Nb2CTX/graphene aerogels for efficient solar-driven steam generation

The development of high-efficiency photothermal conversion materials for seawater desalination is crucial to mitigating the global freshwater shortage crisis. The present investigation is aimed to prepare three-dimensional cylinder Nb2CTX/graphene aerogels (Nb2CTX/GAs) by a combined hydrothermal and freeze-drying process as a photothermal conversion material for solar-driven steam generation. The broad adsorption spectrum, porous microstructure, and excellent hydrophilicity account for the superior photothermal conversion performance of Nb2CTX/GAs. A high evaporation rate of 1.423 kg·m2h−1 was achieved as well as an exceptional solar steam conversion efficiency of 89.6% under one sun irradiation. Furthermore, Nb2CTX/GAs exhibited excellent cyclic stability of photothermal conversion. This work attempts to reveal the great prospect of Nb2CTX/GAs in seawater desalination applications.

Asymmetric solar evaporator with salt-resistance capability for freshwater and energy generation

Solar-driven steam generation is a promising solution for addressing the pressing challenges of freshwater and energy scarcity, but the accumulation of salt on the evaporator surface hinders performance by reducing sunlight absorption and blocking water transport. To overcome this limitation, we developed an innovative Janus solar evaporator with asymmetric surface wettability that simultaneously generates energy and clean water. The solar evaporator-based niobium nitride (Nb4N5) nanosheets with broadband absorption and high light-to-thermal conversion capability displayed an excellent high evaporation rate of 2.30 kg m−2 h−1 under 1 kW m−2 irradiation, which was 4.8-fold higher than that of melamine foam evaporator. Notably, the Janus evaporators displayed an excellent evaporation rate of up to 2.10 kg m−2 h−1 in 20wt.% NaCl solution. Furthermore, during steam generation, the hybrid evaporator with a thermo-electricity module produced an open-circuit voltage of 135 mV and a short-circuit current of 14.6 mA under two sun irradiation. Our findings demonstrated that the Janus evaporator with salt-resistance property has significant potential for simultaneous steam and electricity production, offering a promising solution to simultaneously address the water and energy crisis.

Multifunctional fabrics embedded with polypyrrole-silver/silver chloride nanocomposites for solar-driven steam generation and photocatalytic decontamination

Solar-driven water evaporation is considered as promising and eco-friendly technology for freshwater acquisition. Yet, hazardous substances such as organic pollutants and bacteria present in wastewater can adversely deteriorate the quality of clean water and consequently take a toll on human health. Herein, multifunctional fabrics were fabricated by embedding polypyrrole-silver/silver chloride (PPy-Ag/AgCl) nanocomposites in situ on the surface of cotton fabric, thus integrating photothermal effect, photodegradation of organic contaminants and antibacterial activity. The surface plasmon resonance (SPR) effect of Ag nanoparticles and π-electron delocalization structures of PPy not only enhanced the light absorbance and photothermal performances, but also promoted the generation and separation of photogenerated charge-carriers of the multifunctional fabrics. Therefore, the multifunctional fabrics demonstrated a notable solar evaporation rate of 1.73 kg m−2h−1 for freshwater production and high photodegradation efficiency for typical organic pollutants such as rhodamine B (RhB), methylene blue (MB) and methyl orange (MO). Meanwhile, multifunctional fabrics showed good antibacterial activities (100% against E. coli and 99.76 ± 0.4% against S. aureus). When treating compound wastewater, the multifunctional fabric could remain efficient rejection rate of organic and inorganic pollutants and showed reliable stability. The multifunctional fabric shows great advantages for comprehensive wastewater purification.

Biomass-based high-efficiency solar-driven interface evaporator based on natural pomelo peel with multi-curvature gradient structure

Interfacial solar-driven steam generation (ISSG) applied to desalination is considered as a promising technology to solve freshwater crisis. However, challenges remain in the high cost of raw materials, complex manufacturing and the inability to scale. In this paper, a novel interfacial solar-driven evaporator based on ultra-black carbon black-coated pomelo peel (UB-PP) is proposed for high-efficiency desalination, the synergistic effect of natural PP with unique structural properties and the surface high absorption rate photothermal material endows the UB-PP evaporator with high evaporation efficiency, in which the unique multi-curvature gradient and interconnected porous structure is the key to achieving superior solar water evaporation. Under the local high photothermal conversion heat on the surface, the ubiquitous structure provides timely self-water supply, fast water transport, water activation and multi-channel steam release, resulting in the UB-PP evaporator with excellent water evaporation rate of 1.81 kg·m−2·h−1 under 1 sun. Benefiting from the "Turning waste into treasure" strategy and simple preparation method, the overall material cost is as low as $2.7 m−2, enabling the practical large-scale application of UB-PP in desalination and providing a cost-effective management strategy for biowaste.

Sugarcane inspired polydopamine @ attapulgite-based aerogels with vertical pore structure for solar-driven steam generation

Desalination using solar-driven photothermal evaporators (SPEs) is of great significance for solving mankind's current shortage of fresh water. Herein, inspired by the vascular bundles for the directed and rapid transport of water and organic pollution such as inorganic salts in the vascular system of sugarcane, a polydopamine (PDA) @ attapulgite (ATP) based biomimetic aerogel (named as PAS aerogels) was prepared for efficient desalination. In PAS aerogels, the ATP gives the aerogel excellent mechanical properties, whereas the PDA gives the aerogel excellent light absorption properties. In the wet state, PAS aerogels have low thermal conductivity (0.24 W ∙ m−1∙ K−1) and low apparent density (0.13 g ∙ cm−3). Indicating that the photothermal evaporation rate of PAS-1.5 aerogel is 1.71 kg ∙ m−2∙ h−1 in pure water under 1 sun irradiation. Meanwhile, it can maintain excellent evaporation performance even in high salt solution with 20% concentration (about 1.50 kg ∙ m−2∙ h−1). Owing to the vertical pore structure of the aerogel, which is similar to that of sugarcane transport tissues, the aerogel has both an adequate supply of water and excellent salt tolerance. Furthermore, outdoor experiment of Yellow Sea water evaporation demonstrates its feasibility in the actual production of desalination.

3D wood-based evaporator for highly efficient solar steam generation

Abstract Interfacial solar-driven steam generation is one of the most promising techniques used to produce clean water. However, achieving rapid water evaporation using solar steam generation devices is challenging because of their two-dimensional (2D) planar structures and confined evaporation areas. The three-dimensional (3D) structural design of evaporation devices improves water evaporation rates, thereby enhancing solar-driven steam generation. This study developed a 3D wood-based evaporator through 3D structure shaping and the flexible treatment of wood that involved coating photothermal materials with tannic acid. Because of the ampliative evaporation area and outstanding absorption, the water evaporation rate of the prepared 3D wood-based evaporator was as high as 2.5 kg m−2 h−1, and the efficiency of energy transformation was up to 101 % under simulated 1-sun irradiation; the evaporation rate and efficiency of energy transformation were considerably higher than those of 2D planar wood evaporators. Furthermore, the effective seawater desalination performance and good durability of the 3D wood-based evaporator were demonstrated. This study provides different insights into the fabrication of high-efficiency wood-based solar steam generators with high prospects for application in seawater desalination.

Hierarchical structure design of sea urchin Shell-Based evaporator for efficient omnidirectional Solar-Driven steam generation

Solar-driven steam generation (SSG) is regarded as a feasible solution to the problem of fresh water scarcity. Although several attempts have been devoted to increase the efficiency of solar-to-steam conversion, it remains difficult to fabricate cost-effective, steady, and multi-angle sunlight-absorbing evaporators from readily available biomass materials. Herein, a novel hierarchical structured SSG evaporator (PDA@Shell-NaClO) is developed through a simple, low-cost, and scalable etching treatment on discarded sea urchin (SU) shells. Attributing to the dedicatedly designed microneedles array structure and porous skeleton structure of the SU shell, this PDA@Shell-NaClO evaporator shows an outstanding average light absorption performance (>90%) in a broad range of angles from 0° to 60° and exceedingly high evaporation rate of 2.81 kg m-2 h−1 under one sun condition. Furthermore, the prepared evaporator also maintains an overall stable evaporation performance and exhibits an excellent durability for a long time of up to two weeks in actual seawater. This full-ocean biomass-based SSG evaporator with plentiful raw material availability offers innovative opportunities for large-scale fresh water production.

Janus biomass aerogel for Highly-Efficient steam Generation, Desalination, degradation of organics and water disinfection

Solar-driven water purification has been deemed as a cheap, green and renewable technology to mitigate water shortage and pollution. Herein, a biomass aerogel with hydrophilic-hydrophobic Janus structure has been prepared as solar water evaporator, which is achieved by partially modifying hydrothermal-treated loofah sponge (HLS) with reduced graphene oxide (rGO). It's a rare design philosophy that HLS serves as a substrate with large pores and hydrophilic properties to ensure continuous and effective water transport, and the hydrophobic layer with rGO modification guarantees good salt resistance in seawater desalination with high photothermal conversion efficiency. As a result, the obtained Janus aerogel, p-HLS@rGO-12, exhibits impressive solar-driven evaporation rates of 1.75 kg m-2h−1 and 1.54 kg m-2h−1 for pure water and seawater respectively, with good cycling stability in the evaporation process. Furthermore, p-HLS@rGO-12 also demonstrates outstanding photothermal degradation of rhodamine B (greater than98.8 % in 2 h) and sterilization of E. coli (nearly 100 % in 2 h). This work offers an unusual approach to achieve highly efficient solar-driven steam generation, seawater desalination, organic pollutant degradation, and water disinfection simultaneously. The prepared Janus biomass aerogel holds great potential application in the field of seawater desalination and wastewater purification.