Efficient Solar Steam Generation Research Articles

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

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

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

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

Photothermal graphite phase carbon nitride membrane intercalated with polyoxovanadate for efficient solar steam generation

Graphite phase carbon nitride (GCN) has shown promising prospects in diverse fields due to its exfoliating two-dimensional (2D) layered structure, adjustable electronic properties, wide absorption of visible light, and excellent chemical stability. It is crucial to accurately regulate and functionalize the intercalation space of 2D membrane materials for specific functions. Herein, we demonstrate the first GCN-based photothermal membrane for efficient solar steam generation. The polyoxovanadate anion was intercalated in between protonated GCN layers via an electrostatic interaction strategy, which enlarged the layer spacing up to ∼12.4 Å and increased the water and salt ions transport capability. Owing to the excellent photothermal conversion efficiency of polyoxovanadate, the polyoxovanadate-intercalated GCN membrane fabricated by suction filtration exhibited effective absorbance in full solar spectrum (>95.5 %) and achieved efficient solar steam generation (2.62 kg m−2 h−1 under 1 sun) when floating on water. The long-term durability test showed that the evaporation performance is stable and no salt precipitation observed. These findings not only expand the functional applications of carbon nitride materials, but also provide a new strategy for solar desalination.

Enhanced near-infrared absorption of Cs0.32WO3 nanoparticles for efficient interfacial solar steam generation

Solar steam generation has gained significant attention as a promising method for clean and sustainable water purification and desalination. The spectral absorption performance of the photothermal conversion material directly affects its thermal conversion efficiency. This research investigates the enhanced near-infrared absorption of Cs0.32WO3 nanoparticles for efficient interfacial solar steam generation. In this study, Cs0.32WO3 nanoparticles were synthesized using a simple co-precipitation and heat treatment method. The synthetic nanoparticles were then incorporated into a porous membrane to create a photothermal conversion material for solar steam generation and their near-infrared absorption properties were characterized. The experimental results demonstrated that the Cs0.32WO3 nanoparticles effectively converted solar energy into heat, resulting in efficient interfacial steam generation. The membrane showed a high evaporation rate of of ∼ 3.15 kg·m−2·h−1 under one sun illumination. The findings of this study provide valuable insights into the design and development of efficient solar steam generation systems using near-infrared absorption nanomaterials.

A bioinspired hollow fiber-based evaporator with hybrid photothermal enhancement for efficient solar steam generation

Harvesting sustainable solar energy for interface steam generation is an appealing technological approach to address current water shortages. However, practical implementation has been hindered by suboptimal steam generation rates and significant heat losses. This study proposed a pioneering approach by designing and validating a cost-effective and scalable carbonized kapok fiber-based aerogel (Ni-NCNTs/KF), drawing inspiration from the structural characteristics of penguin feathers. The vertically-aligned Ni-NCNTs array on the surface of the hollow KF achieves exceptional sunlight absorption exceeding 96 %, attributed to a hybrid enhancement mechanism and effective light trapping. Furthermore, the distinctive core–shell architecture of Ni-NCNTs facilitates surface plasmon resonance and fosters efficient electron transfer at the interfaces, resulting in heightened light-to-heat conversion efficiency. The strategic configuration comprising a hydrophobic KF and a hydrophilic Ni-NCNTs effectively regulates water evaporation by spontaneously restricting water transport. Notably, the inherent macroporous nature of kapok fibers (KF) significantly mitigates thermal conductivity, thereby minimizing heat conduction losses. Consequently, Ni-NCNTs/KF exhibits a remarkable water evaporation rate of 3.22 kg m−2h−1 in seawater and an efficiency of 90.5 % under 1 sun. This innovative research not only furnishes a robust design paradigm for the advancement of efficacious photothermal materials but also presents a promising solution for desalination.

Thermoresponsive Janus hybrid hydrogel for efficient solar steam generation

Solar-driven interfacial evaporation technology stands out as a promising solution for sustainable freshwater production. To achieve sustained and efficient water evaporation, it is crucial to carefully modulate the distribution of water content within the solar evaporator. In this study, a novel light-temperature responsive composite hydrogel-based solar evaporator was successful constructed. This involved the incorporation of a hydrophilic backbone (polyacrylamide) and a highly efficient solar absorber (multi-walled carbon nanotubes) into a temperature-sensitive hydrogel polymer backbone (poly (N, N-diethylacrylamide)). Due to its low critical solution temperature, the evaporator can undergo a hydrophilic/hydrophobic phase transition alternating day and night conditions. In natural sunlight, the upper hydrogel evaporation region is rendered hydrophobic, minimizing heat loss and preventing salt crystallization. Simultaneously, the bottom water delivery region is hydrophilic to ensure sufficient water supply. At night, the evaporator absorbs water and dissolves, thereby facilitating the rapid return of highly concentrated brine. Leveraging the spontaneously formed Janus structure, the photo-hydrothermal hydrogel achieves an impressive evaporation rate of 2.74 kg m−2 h−1 and exhibits excellent salt resistance. The notable water evaporation performance and robust salt resistance provide exciting possibilities for achieving ultrafast solar water purification.

Bacterial cellulose-based porous Janus aerogels for efficient interfacial solar steam generation

Interfacial solar steam generation (ISSG) is considered a green and inexpensive technology to solve water scarcity problems. Currently, it still needs to pursue a fast evaporation rate, high-quality fresh water production, and excellent mechanical properties. Herein, Janus aerogels with hydrophilic and hydrophobic structures were prepared by effective spraying of polydimethylsiloxane (PD on the upper surface of bacterial cellulose (BC) /carbon black (CB) /agar powder composites (named JBCA). After a series of experiments, the results showed that the obtained JBCA evaporator had a water evaporation rate of 1.83 kg m−2 h−1 under 1000 W m−2 solar radiation. Meanwhile, the same high evaporation rate (1.63 kg m−2 h−1) was obtained in high salinity (20 wt%) solution. More importantly, the ion removal rate for real seawater was more than 99 %. The results of outdoor evaporation experiments and sustainability analyses indicated that this low-cost material with Janus structure had great potential for practical applications.

Biomass-Based Antibacterial Hybrid Engineering Hydrogel for Efficient Solar Steam Generation

Biomass-Based Antibacterial Hybrid Engineering Hydrogel for Efficient Solar Steam Generation

Ultralight anisotropic Ti3C2Tx MXene/Carbon nanotube hybrid aerogel for highly efficient solar steam generation

Solar steam generation (SSG) has been considered as a promising method to produce fresh water from seawater. Due to high light absorption and excellent chemical stability, carbon nanotube (CNT) has been widely used for SSG. However, it is still challenge to simultaneously realize high water evaporation rate and energy efficiency for CNT based solar steam generator. Herein, ultralight anisotropic Ti3C2Tx MXene/carbon nanotube (A-Ti3C2Tx/CNT) aerogels are designed and fabricated for highly efficient SSG. The combination of CNT and Ti3C2Tx MXene endows the hybrid aerogel with high light absorption and effective localized surface plasmon resonance (LSPR), resuting in enhanced light-to-heat conversion efficiency. The porous structure of aerogel leads to multiple scattering and absorption, further contributing to the photothermal conversion process. Moreover, the low thermal conductivity of aerogel structure effectively reduces the heat loss to environment. Through tailoring the anisotropic channel, the A-Ti3C2Tx/CNT hybrid aerogel with average channel size of 80 μm possesses most efficient water transport due to the capillary effect and formation of intermediate water. Therefore, the A-Ti3C2Tx/CNT hybrid aerogel exhibits high average light absorption of 95.68% in the wavelength range of 200–2500 nm, excellent water evaporation rate of 2.10 kg m−2 h−1 under 1 sun irradiation (1 kW m−2) with a high energy efficiency of 93.4%, and remarkable durability with 7 days continuous water evaporation. The A-Ti3C2Tx/CNT hybrid aerogel also shows high resistance to salt crystallization due to its high salt transport flux of 1.90 kg m−2 h−1. This work offers a prospective strategy for constructing highly efficient solar steam generator with stable performance for practical application in seawater desalination.

Cost-Effective and Scalable Solar Interface Evaporators Derived from Industry Waste for Efficient Solar Steam Generation.

Interfacial solar steam generation for sustainable and eco-friendly desalination and wastewater treatment has attracted much attention. However, costly raw materials and complex preparation processes pose constant challenges to its wide promotion. Herein, a novel, cost-effective, and scalable strategy is presented for preparing solar interface evaporators using industrial waste as a raw material. Modified polyethylene foam evaporators (M-EPEs) are simply prepared by drilling and then hydrophilic modification of industrial waste (EPE-1). M-EPEs not only retain the strong mechanical properties and thermal insulating properties (0.047 W·m-1·K-1) of EPE-1 but also exhibit superhydrophilicity and strong light absorption (over 90%). M-EPEs achieve a high evaporation rate of 1.497 kg·m-2·h-1 and photothermal efficiency of up to 93.8% under 1 kW·m-2 solar illumination. Moreover, it has excellent stability and salt tolerance. Our work addresses the environmental issues of recycling polyethylene waste and provides a facile and efficient strategy for designing low-cost, large-scale solar interface evaporators for desalination.

Unique photothermal material: Copper phosphate (Cu3P2O8) with broadband visible-to-near-infrared absorption properties for efficient solar steam generation

Effective harnessing of renewable solar energy in interfacial solar steam generation (ISSG) is a promising solution for addressing freshwater scarcity worldwide. Therefore, the development of photothermal materials plays a pivotal role in achieving efficient ISSG performance. This paper reports on an innovative photothermal material, copper phosphate (Cu3P2O8; CuPO), with broadband visible-to-near-infrared (Vis-to-NIR) absorption for ISSG. CuPO exhibited favorable characteristics, including extensive light absorption across the Vis to NIR spectrum (500–2200 nm), low thermal conductivity (0.64 W/m·K), high photon-to-heat conversion efficiency (87.9 %), and inherent hydrophilicity. When subjected to simulated sunlight (AM1.5G, 100 mW/cm2), the CuPO-coated polyurethane membrane demonstrated remarkable water evaporation performance (2.05 kg/m2·h) and ISSG efficiency (95.0 %). Notably, employing an ultraviolet cutoff filter (< 450 nm) revealed a substantial NIR absorption contribution of CuPO, surpassing 80 % of its overall performance. Moreover, the CuPO photothermal membrane exhibited durable ISSG performance over 25 cycles, underscoring the structural robustness and resilience of CuPO. Our findings offer a promising foundation for designing cost-effective, high-performance ISSG systems utilizing copper-based complex oxides.

Full-spectrum-responsive Ti4O7-PVA nanocomposite hydrogel with ultrahigh evaporation rate for efficient solar steam generation

Solar steam generation (SSG) via interfacial photothermal conversion has emerged in sustainable seawater desalination and sewage purification. One of the grand challenges is that low light absorption generally limits photothermal materials on water evaporation rates and insufficient on-board performance for real practice. Herein, we propose a “molecular/phase dual-locking” strategy to homogeneously composite Magnéli phases like Ti4O7 nanoparticles and poly(vinyl alcohol) (PVA) by chemical-physical bi-crosslinking. As-obtained Ti4O7-PVA nanocomposite hydrogels (TPNHs) exhibit a narrow bandgap (~0.81 eV) for highly efficient sunlight absorption all through UV–vis–NIR full-spectrum wavelengths (up to ~99.56 %) and enable a record high evaporation rate of ∼4.45 kg m−2 h−1 with outstanding energy efficiency (~90.69 %) under one sun irradiation. A 20−day continuous test in real seawater manifests excellent long-term performance stability of TPNHs without salt accumulation. We further demonstrate the SSG efficacy of such hydrogels by applying them for efficient desalination/purification of varying seawater and sewage samples with low-to-high salinity, strong acids/bases, heavy metal ions, and organic dyes. This “molecular/phase dual-locking” design strategy and resultant Ti4O7-PVA nanocomposite hydrogels present a promising methodology to boost practical applications for seawater desalination and sewage purification.

Highly Efficient Solar Steam Generation and Desalination through Gourd‐Flesh Templated Polypyrrole Composite

Solar steam generation (SSG) is regarded as a promising technique due to its potential in seawater desalination. Photothermal conversion materials derived from biomass are good evaporators for SSG because of their sustainability and high efficiency. Herein, 3D‐cylindrical‐structured composite materials based on gourd flesh and polypyrrole (GPPY) are designed and used for high efficient SSG. The polypyrrole layer is deposited on the gourd flesh to provide broad optical absorption ability and high photothermal conversion efficiency. In addition, gourd flesh with porous structure can act as thermal insulators, confine the generated heat within the evaporative surface, and facilitate the efficient transport of water to the photothermally active area. Based on these characteristics of the composite, the evaporator made of GPPY can achieve a high evaporation rate of (1.63 kg m−2 h−1), and a superior photothermal conversion efficiency 95.8% under 1 solar irradiation (1 kW m−2). The GPPY can be expected to be a practical photothermal conversion material for commercial SSG based on its high efficiency and sustainability.

Multifunctional aerogel with antibiofouling properties for efficient solar steam generation and seawater desalination

Water purification through solar steam generation is an emerging renewable technology with a massive capacity for freshwater generation. However, designing a multifunctional evaporating system with efficient solar-driven steam conversion along with seawater desalination is still a challenge for large scale freshwater generation. Herein, we propose a design for multifunctional photothermal aerogel containing Ag3VO4 nanoparticles incorporated in reduced graphene oxide with prominent characteristics of large surface area, higher porosity, and surface roughness. The proposed aerogel is fabricated via a facile method and can be used as an all-in-one system for water decontamination via solar steam generation, photocatalytic degradation/disinfection of organic pollutants and desalination of seawater simultaneously. The photothermal aerogel simply floats on air-water interface, with a higher flux of localized heat at the surface that efficiently promotes water evaporation at a rate of 2.1 kg/(m2 h). Moreover, the aerogel can denaturalize microorganism and desalinate seawater even under saline conditions. We anticipate that such an efficient and stable photothermal aerogel will offer a sustainable strategy for water purification via desalination, decomposition, and solar steam generation allowing us to address the current clean water crisis on a large scale.

Harvesting solar energy with a Ni-MOF-based evaporator for efficient solar thermal storage and steam generation

A hybrid solar evaporator comprising a Ni-based metal–organic framework material and a phase change material composite was fabricated for high performance solar-thermal energy storage and continuous solar vapor generation.

Cuttlefish ink nanoparticles-integrated aerogel membranes for efficient solar steam generation

Cuttlefish inks offer nano-solar-absorbers for obtaining freshwater through interfacial evaporation.

Vertical porous aerogel based on polypyrrole and bimetallic modified β-cyclodextrin polymer-chitosan for efficient solar evaporation

Solar-driven interfacial evaporation (SDIE) stands out as a prospective technology for freshwater production, playing a significant role in mitigating global water scarcity. Herein, a cyclodextrin polymer/chitosan composite aerogel (PPy-La/Al@CDP-CS) with vertically aligned channels was prepared as a solar evaporator for efficient solar steam generation. The vertically aligned pore structure, achieved through directional freezing assisted by liquid nitrogen, not only improves water transport during evaporation but also enhances light absorption through multiple reflections of sunlight within the pores. The polypyrrole particles sprayed on the surface of the aerogel acted as a light-absorbing layer, resulting in an impressive absorbance of 98.15 % under wetting conditions. The aerogel has an evaporation rate of 1.85 kg m−2 h−1 under 1 kW m−2 irradiation. Notably, the vertical pore structure of the aerogel allows it to exhibit excellent evaporation performance and salt resistance even in highly concentrated salt solutions. Furthermore, this aerogel is an excellent solar-driven interfacial evaporator for purifying seawater and fluoride-containing wastewater. This photothermal aerogel has the advantages of excellent performance, low cost, and environmental friendliness, and thus this work provides a new approach to the design and fabrication of solar photothermal materials for water treatment.

Natural down fiber-reinforced and polypyrrole-modified silk fibroin composite aerogel for efficient solar steam generation toward seawater desalination and wastewater treatment

Poor mechanical properties and low photothermal efficiency of silk fibroin (SF)-based aerogels are current challenges that need to be addressed. Herein, SF composite aerogel was developed to enhance the mechanical properties through physical interpenetration of natural down fiber (Df) and hydrogen bonds formed among SF, Df, and polypyrrole (PPy) and to improve the evaporation performance via in-situ polymerization of PPy. The resultant Df/PPy@SF aerogel showed significant improvement of compressive stress (194.29 kPa), which was 6.96 times than that of SF aerogel (27.91 kPa), and also good compression resiliency. Furthermore, due to uniform distribution of PPy and high porosity of 95.27 %, Df/PPy@SF aerogel possessed high light absorbance of 99.87 % and low thermal conductivity (0.043 W·m−1·K−1). Thus, the Df/PPy@SF aerogel evaporator demonstrated high evaporation rates of 2.12 kg·m−2·h−1 for 3.5 wt% saline water, 2.04–2.15 kg·m−2·h−1 for various dye water, and 2.10 kg·m−2·h−1 for actual dye wastewater. Moreover, the developed aerogel exhibited evaporation stability and outstanding salt-resistance when treating seawater due to continuous water supply by superhydrophilic porous aerogel. Therefore, these findings demonstrate the excellent performance of Df/PPy@SF aerogel and will inspire further research on developing natural fiber-reinforced aerogels for use in the fields of solar water evaporation, energy, and other related applications.

A Fe-Ni-MOF-74@bamboo photothermal evaporator for efficient solar steam generation

Solar-driven interfacial steam generation is considered as a promising technology to solve the shortage of fresh water resources by using inexhaustible solar energy. In this field, the challenge comes from the design of an interfacial evaporator with high performance in photothermal conversion, water activation (low evaporation enthalpy) and water delivery ability. Herein, a composite evaporator was prepared by in-situ composition of bamboo and Fe-Ni-MOF-74 and subsequently simple carbonization. In this evaporator, bamboo ensures that water quickly reaches the evaporation interface, and rich hydrophilic groups have the function of activating water molecules. Fe-Ni-MOF-74 enhances photothermal effect due to bimetallic coordination. In addition, the hydrophilic feature and the pore structure strengthen the water activation and water absorption capacity. Meanwhile, carbonization under mild conditions compensates for the light absorption. As an outcome, the evaporator achieves high evaporation rate (3.61 kg m−2 h−1), high solar-vapor conversion efficiency (153 %), low evaporation enthalpy (1.517 kJ g−1), good stability in saline water and antibacterial function. Furthermore, both seawater and wastewater purified by the evaporator comply with drinking water standards. In the outdoor experiment, the evaporator can collect water of 4.01 kg m−2 during one daylight. The result highlights great potential of bamboo and MOF composite evaporator for producing fresh water using solar energy.

Peak-like three-dimensional CoFe2O4/carbon nanotube decorated bamboo fabrics for simultaneous solar-thermal evaporation of water and photocatalytic degradation of bisphenol A

Catalytic CoFe2O4 and solar-thermal carbon nanotube decorated bamboo fabrics (CCBF) are fabricated for integrating efficient solar steam generation from wastewater with catalytic degradation of its organic contaminants. Thanks to the numerous porous channels and polar groups of bamboo fabric and the efficient solar-thermal energy conversion of black carbon nanotubes, the porous and hydrophilic CCBF exhibits fast upward transport of water, efficient solar light absorption, and high solar-thermal energy conversion efficiency. The decorated CoFe2O4 not only enhances the solar-thermal energy conversion efficiency of CCBF but also activates potassium peroxymonosulfate to generate abundant highly active species for catalytic degradation of bisphenol A (BPA). Furthermore, folding the CCBF into a peak-like 3D evaporator can enhance solar energy utilization, and gain environmental energy for promoting solar-thermal water evaporation and catalytic degradation performances. The 3D CCBF evaporator achieves a water evaporation rate of 2.72 kg m–2 h–1 under 1-sun irradiation. Meanwhile, 100% of the BPA in the seawater can be degraded within 10 min. An exceptional high purification efficiency of 27.72 kg m–2 h–1 is achieved with the 3D evaporator during a long-term treatment of BPA-containing seawater under 1-sun irradiation. This work demonstrates efficient purification of seawater/wastewater with both metal ions and organic pollutants by simultaneous solar-thermal evaporation of water and catalytic degradation of organic pollutants.