Solar-driven Interfacial Water Evaporation Research Articles

Three-dimensional NiO/Ni self-floating porous composite materials for efficient solar interfacial evaporation

The scarcity of freshwater resources and energy crisis are major challenges to the progress of human society. Recently, solar-driven interfacial water evaporation utilizes photothermal conversion materials to convert solar energy into thermal energy, which possesses great application potential in seawater desalination and sewage treatment. Here, we fabricated porous nickel sponge (NSP) composite photothermal material (NiO-NSP) containing abundant NiO nanoneedles array. This in situ-grown NiO with enhanced bonding between photothermal material and substrate can be used as a solar absorber directly without consuming additional photothermal material compared to conventional coating and cladding on the carrier surface. Due to the multi-scattering induced light trapping effect of the semiconductor NiO nanoneedles array on the surface of nickel fibers, resulting in light absorption up to 96.5 %. NiO-NSP evaporators have an abundance of interconnected porous channels for water supply, which results in strong capillary action to pump water to the evaporation interface efficiently. Moreover, the highly dispersed nanoneedles array expand the evaporation surface area. Consequently, the NiO-NSP evaporator delivers an excellent evaporation rate of 1.78 kg m−2 h−1 and a photothermal conversion efficiency of 84.7 % at one sun radiation. In addition, the micron-sized porous mesh structure of NiO-NSP dissolve salt crystals and diffuse them downward into the bulk brine, exhibiting excellent salt resistance and remarkable seawater desalination stability. Moreover, NiO-NSP solar evaporators has been demonstrated to possess excellent ability to purify dye and heavy metal ion wastewater. Therefore, the NiO-NSP high-performance evaporator produced by straightforward process proved to be suitable for solar seawater desalination and wastewater purification.

Preparation of nanoporous TiOx powder and its enhanced photocatalytic N2 to NH3 conversion by solar-driven interfacial water evaporation

At present, the limited efficiency in ammonia generation poses significant challenge to the widespread practical implementation of photocatalytic nitrogen reduction to ammonia (PNRN). In this study, we synthesized a nanoporous TiOx powder (Alloy-RTO) by rapid breakdown anodization of TA13 alloy and subsequent magnesiothermic reduction. The Alloy-RTO exhibited superior photothermal and photocatalytic properties owing to its multicomponent and interconnective nanoporous structure, and the electronic band structure is suitable for efficient PNRN. Notably, through synergistic integration of PNRN with solar-driven interfacial water evaporation technology (SDIWE), the ammonia production rate was further enhanced, and a multifaceted role of SDIWE in enhancing PNRN was proposed: (1) increasing temperature of Alloy-RTO to promote PNRN; (2) raising temperature to accelerate ammonia water decomposition and facilitate PNRN; and (3) generating plenty of gaseous water to accelerate PNRN. This study presents an effective strategy for preparing nanoporous TiOx and highlights the pivotal role of SDIWE in promoting PNRN.

Harnessing overlapped temperature-salinity gradient in solar-driven interfacial seawater evaporation for efficient steam and electricity generation

Solar-driven interfacial water evaporation (SIWE) offers a superb way to leverage concentrated solar heat to minimize energy dissipation during seawater desalination. It also engenders overlapped temperature-salinity gradient (TSG) between water-air interface and adjacent seawater, affording opportunities of harnessing electricity. However, the efficiency of conventional SIWE technologies is limited by significant challenges, including salt passivation to hinder evaporation and difficulties in exploiting overlapped TSG simultaneously. Herein, we report self-sustaining hybrid SIWE for not only sustainable seawater desalination but also efficient electricity generation from TSG. It enables spontaneous circulation of salt flux upon seawater evaporation, inducing a self-cleaning evaporative interface without salt passivation for stable steam generation. Meanwhile, this design enables spatial separation and simultaneous utilization of overlapped TSG to enhance electricity generation. These benefits render a remarkable efficiency of 90.8% in solar energy utilization, manifesting in co-generation of solar steam at a fast rate of 2.01 kg m−2 h−1 and electricity power of 1.91 W m−2 with high voltage. Directly interfacing the hybrid SIWE with seawater electrolyzer constructs a system for water-electricity-hydrogen co-generation without external electricity supply. It produces hydrogen at a rapid rate of 1.29 L h−1 m−2 and freshwater with 22 times lower Na+ concentration than the World Health Organization (WHO) threshold.

Enhanced interfacial evaporation of CF@NC fabric via coupled photo-thermal and Joule-heating effect

To address the challenges of global water pollution and scarcity, solar-driven interfacial water evaporation has emerged as a viable method for producing clean water. Nevertheless, the efficacy of most extant interfacial evaporation systems were contingent upon abundant sunlight, thereby constraining their utility. To surmount the limitation, this study introduced a coupled tunable photo-thermal and Joule-heating process for interfacial evaporation utilizing carbon fiber (CF) modified by N-doped carbon nanotubes (NC). The CF@NC had highly graphitized structure, excellent light-absorbing ability and hydrophilicity, which made it suitable for photo-thermal and Joule-heating conversion. Under the coupled effect of photo-thermal and Joule-heating, the evaporation rate reached 10.37 kg·m−2·h−1 with 1 sun and 2.5 V, while the rate was 1.81 kg·m−2·h−1 under only 1 sun and 7.63 kg·m−2·h−1 with 2.5 V. Meanwhile, the CF@NC fabric evaporator also showed promising potential in salt tolerance and dye wastewater treatment. Under continuous all-day operation, a superior purification performance was achieved, which realized long periods of no salt operation and effectively remove the Rhodamine B and methyl orange in the water. Considering the high evaporation rate and reliable water yields obtained from simulated seawater and dye wastewater, the CF@NC fabric evaporator hold great promise for highly efficient purification.

Green and efficient electrolysis of seawater using carbon nanotube-based hybrid films

Producing hydrogen by splitting seawater using renewable energy is a promising way to obtain a clean energy carrier. However, neither direct electrolysis nor post-desalination electrolysis techniques work well due to the complex composition of seawater and the large amount of energy needed. We report a solar-driven continuous seawater electrolysis system (CSES) by which seawater could be first distilled into pure water and then electrolyzed to obtain green hydrogen. The CSES is based on a multi-functional single-wall carbon nanotube (SWCNT)-based hybrid film, which is composed of a partially oxidized SWCNT layer and a high-entropy alloy nanowires/SWCNT layer. The SWCNT-based hybrid film functions as both a solar-driven interfacial water evaporation membrane and a water-splitting electrode. A high seawater evaporation efficiency of 1.22 kg m−2 h−1 under 1 sun irradiation and a low overpotential of 119 mV and 220 mV for hydrogen evolution reaction along with 330 mV and 356 mV for OER at current densities of 100 and 300 mA cm−2, respectively, are demonstrated. The CSES has a hydrogen productivity of 1.04 × 104 L day−1 m−2 (under a constant current of ∼1.4 A) and works continuously for 100 h without any external energy consumption.

Fe-based metal organic frameworks decorated wood for efficient solar-driven interfacial water evaporation

The shortage of water resources in today's society requires humans to produce freshwater resources under harsh conditions (seawater desalination or sewage purification). Using solar energy as a heat source for water evaporation is the most environmentally friendly and sustainable way to produce fresh water. Traditional solar evaporation systems have large heat losses and low evaporation efficiency. Solar-driven interface evaporators can concentrate heat at the water–air interface, thus greatly improving the efficiency of water evaporation. The development of photothermal materials with excellent light-to-heat conversion ability is of great significance for the development of solar-driven interfacial evaporators. Herein, we introduce an evaporator based on wood, which is obtained through delignification, followed by freeze-drying treatment, then surface carbonization, and finally Fe-based metal organic frameworks loading, for effective solar-interfacial evaporation. The outstanding feature of the developed evaporator is that it exhibits excellent ultraviolet to near-infrared light absorbing capacity and high heat conversion efficiency, which can realize the rapid increase of the evaporator’s surface temperature within 10 min. On the other hand, the high hydrophilicity of the evaporator ensures rapid water transportation. Therefore, the evaporation rate of metal organic frameworks decorated wood reaches a value up to 1.81 kg m−2 h−1 and exhibits an evaporation efficiency of 89 % under the irradiation of one solar intensity (1 sun-illumination or 1 kW m−2). In the self-desalination capacity test, the composite evaporator with geometric dimensions of 4 cm2 achieved an efficient removal of 1 g of NaCl in one hour. In the simulated sewage purification experiment, the purification rate of tetracycline, methyl orange, and rhodamine B solutions reaches 93.2 %, 100 %, and 99.3 %, respectively, indicating that the developed evaporator can be considered as potential candidate for environmental safety applications.

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.

All-in-one chitosan-based aerogel with a semi-clad structure for solar-driven interfacial evaporation

Solar-driven interfacial water evaporation is a promising technique for recovering clean fresh water and alleviating water scarcity. In this work, an all-in-one chitosan-based composite aerogel with a highly porous semi-clad structure was fabricated. In the process of interfacial water evaporation, the hydrophilic outer layer of the aerogel efficiently transported water to the upper surface through two-dimensional transport channels. Simultaneously, it rapidly converted absorbed sunlight into heat, demonstrating excellent photothermal conversion capabilities for efficient water evaporation. The hydrophobic inner core enabled the aerogel to float stably on the water surface, and had a low thermal conductivity to reduce heat dissipation into the water body. Under 1 sun illumination (1 kW m−2), the composite aerogel showed an evaporation rate of up to 1.547 kg m−2 h−1, corresponding to an evaporation efficiency of 91.47 %. Notably, the composite aerogel demonstrated high stability and recyclability in desalination and heavy metal wastewater treatment, which had great potential in recovering both clean water and heavy metal salts. The evaporator with a semi-clad structure had practical applications in solar desalination and sewage treatment due to its stable and efficient evaporation performance and simple preparation method.

Trapping waste metal ions in a hydrogel/coal powder composite for boosting sewage purification via solar-driven interfacial water evaporation with long-term durability

The improper disposal of effluents contaminated with waste metal ions poses significant threats to clean water resources. Recently, solar-driven interfacial water evaporation has gained increasing interests for sustainable water purification, nevertheless, the presence of various hydrated metal ions from industrial effluents makes it challenging for conventional distillers to achieve efficient purification performances. Herein, a waste metal ion trapping strategy based on a novel solar vapor generator (SVG) toward highly efficient solar-driven sewage purification with prolonged durability is reported. This SVG is constructed based on a polyion complex (PIC) hydrogel/coal powder composite (PCC), where the PIC skeleton provides metal ion entrapment capabilities, and the low-cost coal powders act as solar absorbents. PCC enables improved solar-driven sewage purification from two aspects: first, the entrapped multivalent ions help to activate the water molecules inside PCC and lower water evaporation enthalpy, leading to enlarged evaporation rate; second, the strong interactions between the multivalent metal ions and polyelectrolyte chains aid in stabilizing their porous structure and maintaining continuous water transport capabilities. The resultant PCC-based SVG demonstrated high evaporation rate up to 3.6 kg · m−2· h−1 in simulated industrial sewage under one sun illumination, as well as stable and efficient clean water generation in actual coal washery wastewater even for three weeks. We envision that the rational design of SVG with ions trapping capabilities and cost-effective solar absorbers should broaden the practical applications of SVG for harsh wastewater treatment.

Flexible hierarchical polypyrrole-coated Cu-BTC MOFs photothermal textile for efficiently solar water evaporation and wastewater purification

Solar-driven interfacial water evaporation (SDIWE) endures a significant potential for producing clean water from seawater and wastewater because it requires no additional energy source. Photothermal materials with efficient solar absorption and pollutant removal capabilities are critical for SDIWE. However, an efficient and facile strategy to prepare a high-performance and flexible photothermal material and simultaneously prevent the salt accumulation for efficient and long-term steady evaporation to produce potable water from seawater and wastewater is still a challenge. Herein, based on the MS and ALD processes, two novel flexible photothermal materials are synthesized using the flexible polyester fabric substrate, hierarchical metal–organic framework Cu-BTC MOFs, and polypyrrole (PPy) as a light-absorption layer. In particular, under the synergistic effect of the hierarchical porous Cu-BTC MOFs and PPy with excellent solar absorption, the flexible photothermal material possesses excellent light absorption (92.58 % ∼ 93.98 %), super hydrophilicity, low thermal conductivity, high evaporation rate (1.53 ∼ 1.56 kg m-2h−1 for 15 days), outstanding salt resistance (1.42 kg m-2h−1 at a salinity of 15 wt%), and excellent metal ions and organic pollutants removal capacity after solar evaporation. These multifunctional properties ensure its great application prospect for future freshwater production while also providing a new reference for other applications.

Economic and environmental protection high efficiency solar steam generator: Carbonized starch with porous structure

Solar-driven interfacial water evaporation is an emerging water purification technology. However, the high cost and low evaporation efficiency limit the wide application of solar-driven interfacial water evaporation technology. In this work, we use the dough fermented flour and yeast powder production, and then after fermentation of dough to produce high temperature carbonization of carbon materials, the preparation of the sample surface formed a large number of pits, increased specific surface area and the absorbance of the sample, and increased the solar-thermal conversion efficiency of the sample. It is found that the evaporation rate and evaporation efficiency of the sample made in this work is 1.5 kg m−2h−1 and 94.2 % respectively under one solar irradiation intensity. The maximum surface temperature of the sample can reach 43.3℃ during the experimental test, which has good evaporation performance. It provides a new idea for making economical and environmentally friendly materials in the field of solar-driven water evaporation.

Preparation of polypropylene with photothermal conversion and hydrophilicity by one-step impregnation for efficient interfacial water evaporation

Solar-driven interfacial water evaporation is a technology that is currently attracting significant interest for tackling freshwater scarcity. However, the creation of porous membranes with photothermal conversion and hydrophilicity remains a challenging task. This study utilizes melt-blown polypropylene nonwoven (PP), a substrate with high porosity, low cost and high yield, to prepare evaporation membranes exhibiting photothermal conversion properties. The PP surface was treated with a one-step impregnation method to produce both shell and nanoparticles containing MnO2−x. The addition of MnO2−x grants the PP membranes both photothermal conversion and hydrophilicity simultaneously. Sunlight absorption efficiency of PP membranes covered with MnO2−x (M-PP) is 85.83%, and its hydrophilicity and porosity enable it to form an ultra-thin layer of water during evaporation, promoting rapid escape of vapors. Evaporation rate of M-PP membranes reach 1.02 kg m−2 h−1, much higher than that of PP and bulk water. In addition, M-PP membranes have excellent corrosion resistance, which is potentially valuable in treating wastewater and desalinating seawater.

Hierarchical Cu dendrites@ CuO multifunctional nanowire mesh for solar-thermal clean water production

Solar-driven interfacial evaporation is recognized as an energy-efficient and sustainable approach to combat the global freshwater crisis, particularly in rural areas where continuous energy inputs are limited. Additionally, these regions often lack effective sterilization methods for their water sources. By incorporating photothermal materials with inherent antibacterial properties, water purification can be enhanced without relying on external sterilization steps. Herein, we designed a multi-functional photothermal (MFP) evaporator based on a Cu dendrite@ CuO with abundant nanowires via a template-free method for solar-thermal clean water production. Compared to flat-type structures, the MPF evaporator with its dendritic architecture not only exhibits efficient photon absorption but also expands the evaporation area by over sevenfold, facilitating enhanced water evaporation with an efficient pathway for water transfer. Under 1 kW m−2, the MFP evaporator achieves an impressive evaporation rate of 1.40 kg m−2 h−1 and an efficiency of 87.8 %. Furthermore, the MFP evaporator demonstrates remarkable antibacterial capabilities, effectively inhibiting bacterial growth in raw water by damaging bacterial cell walls. Hence, the as-prepared MFP evaporator exhibits tremendous potential as an innovative system for solar-driven interfacial water evaporation and purification.

A low-cost carbonized Enteromorpha–coated wood for highly efficient solar-driven interfacial water evaporation

A low-cost carbonized Enteromorpha–coated wood for highly efficient solar-driven interfacial water evaporation

Effective solar-driven interfacial water evaporation-assisted adsorption of organic pollutants by a activated porous carbon material

Recently, solar-driven interfacial water evaporation (SDIWE) has attracted worldwide attention owing to its potential use in seawater desalination and wastewater purification. Nevertheless, how to effectively use the inevitable conduction heat loss and eliminate organic pollutants are still challenging. We report the SDIWE- assisted adsorption of organic pollutants by using the conduction heat loss to improve the total energy efficiency of the SDIWE system. Porous carbon (PC) and activated PC were prepared by a simple recrystallizing salt template-assisted carbonization and KOH activation method. After activation, the activated PC sample with a PC : KOH mass ratio of 1 : 4 (PC-A4) has a hierarchical porous structure, a better absorption capacity in the spectral region of 200-2500 nm, a high specific surface area of 1 867.71 m2 g−1 and a large pore volume of 1.04 cm3 g−1. Based on this, PC-A4 has a high evaporation rate and energy efficiency, which can be further increased by regulating the mass of the water body. Subsequently, the conduction heat generated by the SDIWE system was used for SDIWE-assisted adsorption. Notably, the maximum amount of rhodamine B adsorbed by PC-A4 is 1 610 mg g−1 at a conduction temperature of 309 K, which is higher than that of the same sample at 298 K. Consequently, this work offers a promising approach for effectively using the conduction heat loss of the SDIWE system and developing it for water purification.

Construction of a biomimetic wood structure with cellulose nanofiber/molybdenum disulfide hybrid aerogel for highly-efficient solar-driven interfacial evaporation

Solar-driven interfacial water evaporation is a promising solution to water scarcity and pollution problems because it can efficiently convert solar energy into thermal energy and produce sustainable clean water. In this work, inspired by the multi-channel structure in the xylem of plants, cellulose nanofibers (CNF) and molybdenum disulfide (MoS2) nanosheets were selected to construct CNF/MoS2 nanosheets aerogel (CMoA) with vertical pores by directional freeze-drying method. Then we utilized the aerogel as an interfacial solar evaporator. The super-hydrophilic and internal vertical pore structure of this evaporator gives CMoA a high capacity to store and transport water, with a water evaporation rate of 1.81 ± 0.06 kg·m−2·h−1 under 1 sun. The vertical pore structure and the strong ability to transport water of the evaporator also enable the salt on the evaporator surface to diffuse into the bulk water in time, without causing salt deposition. Therefore, CMoA has high salt resistance and stability and can achieve fast evaporation even in high-concentration salt water. In addition, CMoA can also produce water at a rate of up to 10.3 kg·m−2 per day in the outdoor environment. By combining the natural bio-based material CNF with the biomimetic wood structure of aerogel, CMoA has a facile water transport process similar to that of plants. Moreover, our CMoA is a monolayer structure, which makes the preparation process simple and less costly. These multiple advantages make CMoA a promising application for future practical desalination work.

Phonon-Engineered Hard-Carbon Nanoflorets Achieving Rapid and Efficient Solar-Thermal Based Water Evaporation and Space-Heating.

Generation and utilization of green heat produced from solar energy demand broadband absorbers with the elusive combination of strong phonon-driven photon thermalization and, contrastingly, weak phonon-lattice thermal conductivity. Here, we report a new class of porous, nanostructured hard-carbon florets (NCFs) consisting of isotropically assembled conical microcavities for greater light entrapment and efficient broad-band absorption (95% over 250-2500 nm). Resembling marigolds, the NCF exhibits short-range graphitic order that promotes instantaneous and efficient solar-thermal conversion (ηSTC = 87%) while exhibiting long-range intrinsic disorder providing low thermal conductivity (1.5 W m-1 K-1) to minimize thermal loss (13%). Solution processable NCF coatings on arbitrarily substrates (filter paper, terracotta, Cu and Al tubes) generate surface temperature of 400 ± 2 K and exhibit high thermal effusance (519 W s0.5 m-2 K-1) to achieve highest combination of (a) rate of solar-driven interfacial water evaporation (Rw = 5.4 kg m-2 h-1, 2 sun), (b) solar-vapor conversion efficiency (ηSVC = 186%), and (c) ηSTC (87%) among known materials. Such robust performance is retained for beyond 30 days of continuous operation and under different solar power (1 sun to 5 sun). Furthermore, active space heating (outlet air temperature = 346 ± 3 K) using NCF coatings is demonstrated.

Interfacial engineering of MXene-based composite aerogel for high-performance, multifunctional solar steam generator

MXene, an emerging two-dimensional material, has shown its evident application prospects in solar-driven interfacial water evaporation due to excellent photothermal conversion capability. However, MXene still suffers from a few undesirable characteristics in this scenario, including weak stability, self-stacking, and suboptimal optical absorption. To address these issues, in this paper, we fabricated a MXene-based composite aerogel, featuring with interconnected porous structure, broad and high solar absorption, good wettability and photothermal capacity. As our judicious structural and compositional design for the aerogel decreased the evaporation enthalpy of water, the solar steam generator based on the aerogel exhibited an outstanding water evaporation rate as high as 2.31 kg m−2 h−1 under one sun irradiation (and the corresponding solar-to-vapor conversion efficiency reached 90.8 %). Additionally, the aerogel was also designed with an excellent adsorption capacity for removal of heavy metal ions from water as well as a good antibacterial ability, which should be helpful in dealing with the complex working environments for solar steam generators. This work may shed light on the design and development of multifunctional solar steam generators toward practical and sustainable applications.

Transferring heat downward from the evaporation interface to accelerate solar vapor generation

Solar-driven interfacial water evaporation (SIWE) is an important strategy for addressing the world's freshwater shortage. However, the traditional evaporator typically localizes the heat to the evaporation interface. This would increase the radiative heat loss between the evaporator and the environment, resulting in a reduction in the evaporation rate. Herein, a water-energy-balanced evaporator (WEBE) is proposed by accurately adjusting the thickness of the solar absorber. The excess energy is transferred downward to preheat the water, which will be transported to the evaporation interface, instead of being dissipated to the environment. In addition, a unique T-shaped water path is introduced to reduce the contact area between the evaporation interface and the bulk water. These allow the WEBE to decrease the conductive and radiative heat losses by 16.4% in total. Importantly, the WEBE demonstrates a superior evaporation rate due to efficient thermal management and water-energy balance. Under 1 sun (at a solar flux of q = 1 kW m−2) illumination, the evaporation rate reaches 2.02 kg m−2 h−1, which is 1.21 times of the traditional evaporator. This work provides a novel and accessible approach to further increase direct solar vapor productivity for solar desalination.

Hydrogel-based photothermal evaporator for efficient solar desalination and synergistic removal of volatile organic compounds

Solar-driven interfacial water evaporation for freshwater production is deemed as a crucial strategy to solve water resources scarcity. However, when the temperature at the air-water interface reaches 40 °C or higher, distilled water obtained by evaporation becomes contaminated for the complex water source rich in volatile organic compounds (VOCs), and the degree of water purification will be greatly reduced. Therefore, this study reports a carbonized carboxymethyl chitosan (C-CMCS)/sodium alginate (SA) hydrogel solar evaporator (CSE) for the synergistic desalination and removal of VOCs from water in the solar-driven vapor generating process. The CSE not only serves as an elegant photothermal absorber to promote water evaporation, but also continuously intercept VOCs with its super adsorption-photocatalysis ability, realizing the magical effect of evaporation-adsorption-degradation. The results indicated that the removal rate of phenol as the probe pollutant molecule was 95.37 % and the rate of solar water evaporation was 2.24 kg m−2 h−1, which may establish a potential tactics for purification from polluted water existing various VOCs by solar evaporation.