Solar steam generation is used for the production of clean water through evaporation. However, during evaporation, high-boiling organic compounds tend to concentrate in the mother liquor, whereas low-boiling organic compounds evaporate with the steam. In this study, a strategy for full-spectrum solar utilization, in which solar steam generation is coupled with photo-Fenton catalysis, was demonstrated for the production of clean water while treating complex wastewater containing high concentrations of organic pollutants. A highly efficient Fenton catalyst, PB/rGO/PPy powder, was developed by integrating Prussian blue (PB), polypyrrole (PPy), and reduced graphene oxide (rGO). The catalyst offers functionality in Fenton catalysis, photothermal conversion, and photogenerated charge transfer channels. It can degrade 95.2% of methyl orange (MO) in 20 min, with a degradation rate constant of 0.251 min-1. Impressively, a PB/rGO/PPy/PVA composite aerogel was created using porous and water-absorbent polyvinyl alcohol (PVA) as a skeleton, where the degradation ability of MO in both deionized water and wastewater reached 100% under 1-sun irradiation, along with an evaporation rate of 1.62 kg m-2 h-1. This integrated aerogel evaporator can be utilized for producing clean water and treating wastewater containing organic pollutants, which may open new avenues for green technologies with high solar energy utilization efficiencies.

Solar-driven water evaporation, utilizing a combination of photothermal materials and hydrogels, represents a highly promising technology for the efficient collection of clean water. Clean water is typically collected through evaporation followed by condensation. However, due to the high evaporation enthalpy of water, this process requires significant energy input, and the subsequent condensation step is both complex and inefficient. Consequently, the efficient collection of fresh water under natural irradiation conditions continues to present a significant challenge. In this study, we designed a temperature-sensitive PPC-PNIPAm hydrogel for efficient water collection. The PPC-PNIPAm hydrogel is composed of temperature-sensitive poly(N-isopropylacrylamide) (PNIPAm), hydrophilic polyacrylamide (PAm), a multi-walled carbon nanotube (MWCNTs) layer, and a polyethylene glycol (PEG) network. The hydrophilic-hydrophobic transition within the gel is both versatile and reversible, enabling rapid access to liquid water and resulting in high water collection rates. The PPC-PNIPAm-16 hydrogel exhibits a water harvesting rate of 10.33 kg m-2 h-1 under 1 sun irradiation, demonstrating long-term cyclic stability. This study offers a relatively new approach to achieving efficient clean water harvesting.

Solar-driven water evaporation can generate clean steam through phase change and mass transfer processes. However, when dealing with volatile organic compounds (VOCs) contaminated water sources, VOCs tend to volatilize into the vapor during the evaporation process, making separation difficult. This issue can be effectively addressed by utilizing photo-Fenton technology to assist the solar-driven water evaporation process. A novel photothermal catalytic film was successfully prepared by incorporating Prussian blue (PB) and polypyrrole (PPy) onto a slow filter paper substrate. The photothermal conversion ability of PPy was further enhanced by PB, and the temperature increase induced by PPy accelerated the photo-Fenton catalysis process, indicating a synergistic action between photothermal evaporation and photo-Fenton catalysis. The film exhibited outstanding catalytic performances in degrading various VOCs in wastewater, including phenol, methyl orange, methylene blue, and rhodamine B. Notably, the film reached an impressive degradation rate of 99.5 % for methyl orange within 2 h. The assembled 2D interfacial evaporator achieved an evaporation rate of 1.58 kg m-2h- 1 under one sun irradiation (1 kW m- 2). After 40 cycles, the evaporation rate remained constant. This photothermal catalytic film effectively degrades VOCs while stably producing steam, demonstrating significant potential in the treatment of volatile organic wastewater.

Solar photothermal interfacial evaporation represents an approach for water purification and desalination, offering a solution to mitigate global water scarcity. However, the uncontrolled crystallization of NaCl on the evaporator surface during saline water evaporation can reduce evaporation efficiency, block water channels, and degrade the evaporator. In this study, we designed an evaporator that effectively suppresses the crystallization of NaCl (200), thereby regulating the crystal structure and shape of the precipitated NaCl. Besides, a Janus hemispherical evaporation interface was proposed, facilitating the self-shedding of NaCl under gravity. The collecting resistance (FCr) of dendritic NaCl is reduced by about two orders of magnitude than that of cubic NaCl. Under 1 kW m- 2 illumination, the evaporator simultaneously achieved a high NaCl salt collection efficiency of 54.30 % and the evaporation rate of 1.10 kg m- 2 h- 1 when treating 20 wt% saltwater. This work introduces a strategy for salt resource extraction and pure water production.

Adhesive hydrogel-based evaporative cooling, which necessitates no electricity input, holds promise for reducing energy consumption in thermal management. Herein, inspired by the surface attachment of mussel adhesive proteins via abundant dynamic covalent bonds and noncovalent interactions, we propose a facile strategy to fabricate a self-adhesive cooling hydrogel (Li-AA-TA-PAM) using a copolymer of acrylamide (AM) and acrylic acid (AA) as the primary framework. The monomers formed hydrogen bonds between their carboxyl and amide groups, while tannic acid (TA), rich in catechol groups, enhances the adhesion of the hydrogel through hydrogen bonding. The hydrogel demonstrated strong adhesion to various material surfaces, including plastic, ceramic, glass, and metal. Even under high-speed rotation, it still maintains robust adhesion. The adhesion strength of the Li-AA-TA-PAM hydrogel to aluminum foil reached an impressive value of 296.875 kPa. Interestingly, the excellent contact caused by robust adhesion accelerates heat transfer, resulting in a rapid cooling performance, which mimics the perspiration of mammals. Lithium bromide (LiBr) with hydroactively sorptive sites is introduced to enhance sorption kinetics, thereby extending the effective cooling period. Consequently, the operation temperature of commercial polycrystalline silicon solar cells was reduced by 16 degrees C under an illumination of 1 kW m(-2), and the corresponding efficiency of energy conversion was increased by 1.14%, thereby enhancing the output properties and life span of solar cells. The strategy demonstrates the potential for refrigeration applications using viscous gels.

Solar‐driven evaporation using hydrogels and photothermal materials is a promising freshwater harvesting technology. However, due to the difficulty of removing volatile pollutants through evaporation and the fact that the evaporation efficiency has reached its limit, further improving efficiency becomes challenging. Therefore, a material simultaneously possessing low water evaporation enthalpy as well as the ability to inhibit volatile pollutants is desired. In this work, a dense inhibitory layer on the hydrogel framework of polyacrylamide introduced into polyvinyl alcohol is designed to enhance its suppression of volatile pollutants and regulate the water state. This not only reduces the energy demand for evaporation but also makes it more effective in treating wastewater containing volatile pollutant ammonia nitrogen. Finally, a high evaporation rate of 3.0 kg m−2 h−1 and an excellent ammonium rejection rate of 90% for high concentration ammonia wastewater are obtained under 1 kW m−2 illumination. This work opens up new avenues of application for the use of photothermal materials in the use of clean solar energy for the separation of freshwater and volatile small molecules.

Silicon (Si) is considered as one of the most promising anodes for the next-generation lithium-ion batteries (LIBs) owing to its ultra-high specific capacity, low redox potential and the second abundance of elements in the earth's crust. However, drastic volume change will directly cause electrode pulverization, thus leading to low initial coulombic efficiency (ICE) and terrible cycling stability. In this work, a sodium alginate (SA)-carbon nanotube (CNT) derived double carbon-coated Si composite (SA-CNT@Si) was prepared through freeze-drying technique followed by high-temperature carbonization, where SA was utilized to encase Si nanospheres, with CNT serving as the conductive framework that interconnects Si spheres. These composites exhibit improved electrical conductivity and stability throughout the charge and discharge cycles when employed as the anodes in LIBs, demonstrating superior electrochemical properties. The SA-CNT@Si electrode with a mass ratio of Si: SA: CNT = 5: 1: 0.75, achieved a first discharge specific capacity of 2200.8 mAh g- 1 at a current density of 500 mA g- 1 (with the initial three cycles at 100 mA g-- 1 ), along with an ICE of 86.2%. Even after 500 cycles, it maintained a capacity of 607 mAh g- 1 . This study presents a novel approach to designing Si-based anode materials characterized by both high electrical conductivity and structural stability.

The highly efficient degradation and purification of organic pollutants in wastewater by photocatalysis is still challenging. In this study, a piezoelectric potential-activated interfacial electric field (IEF) was constructed to endow BiFeO3@BaTiO3 (BFO@BTO) heterojunction with the ability to serve as a round-the-clock photocatalyst for polluted water remediation. BFO@BTO heterojunction is composed of BiFeO3 nanoparticles decorated on the surface of BaTiO3 nanorods, which shortens the carrier migration path. More importantly, the IEF can be activated and reconstructed under ultrasonic wave irradiation, leading to a lower potential barrier and enhanced separation efficiency for photogenerated carriers. The degradation rate constant k value of BFO@BTO heterojunction reached 0.038 min−1, which was 1.9 and 7.0 times greater than that of piezocatalysis and photocatalysis alone, respectively. It also exhibited excellent stability in three light‒dark cycles for high concentrations (25 mg·L−1) of rhodamine B (RhB) and tetracycline hydrochloride (TC). This study provides a promising strategy for designing highly active photoassisted piezocatalysts for environmental energy utilization and round-the-clock catalysis.

Solar‐driven evaporation using hydrogels and photothermal materials is a promising freshwater harvesting technology. Clean water is generally collected through evaporation and subsequent condensation, which requires high energy input due to the inherent high vaporization enthalpy of water. Therefore, it is a great challenge to harvest fresh water efficiently under natural irradiation. Herein, a temperature‐sensitive polyacrylamide‐poly( N ‐isopropylacrylamide) (A‐PNIPAm) gel is designed to pursue a high water collection rate under low energy input conditions, where the facile and reversible hydrophilic/hydrophobic transition in gels enables the quick acquisition of liquid water. A multifunctional hydrogel (ADS‐PNIPAm) is prepared using polydopamine and sodium alginate with excellent adsorption/filtration properties, which can remove pollutants and generate fresh water rapidly. Consequently, the water collection rate of the ADS‐PNIPAm hydrogel reaches up to 5.89 and 9.8 kg m −2 h −1 under 0.6 and 1 sun irradiation, respectively, which are superior to the previously reported values. Furthermore, ADS‐PNIPAm displays an excellent effect on purifying sewage, such as oils, algae, and dyes pollutants. ADS‐PNIPAm is a promising material for a rapid freshwater generation with solar irradiation only, which provides a new avenue to alleviate water source scarcity.

Solar-driven water purification is considered as an efficient and green method to solve water scarcity. However, creating a hydrogel evaporator with both long-lasting evaporation performance and an efficient reduction in water vaporization enthalpy remains a significant challenge. Herein, a hydrogel with low water vaporization enthalpy was prepared by introducing (3-cyclodextrin ((3-CD) to polyacrylamide. The three-dimensional network structure was obtained via a simple freeze-drying process, and the addition of (3-CD enhanced its hydrophilicity. Due to the hydration of hydroxyl groups on (3-CD, the hydrogel facilitated the formation of intermediate water, substantially reducing the water vaporization enthalpy to 1428 J/g. It enabled the hydrogel to achieve a high evaporation rate of 2.65 kg/m2/h under 1 sun irradiation. Furthermore, the hydrogel demonstrated excellent hydration properties and abundant water transport channels for salt rejection in long-term desalination. After 50 cycles of testing in 3.5% brine, the evaporation rate remained high at 2.38 kg/m2/h. This work provides a sustainable way to develop a highly efficient solar evaporator for clean water production.& COPY; 2023 Elsevier Ltd. All rights reserved.

Hydrogels with soft, skin-friendly properties and high biocompatibility are promising alternatives to traditional sensors. However, balancing electrical conductivity and sensitivity remains a significant challenge. The sensitivity-improved strain sensor was designed by reduced graphene oxide (rGO) reinforced polydopamine (PDA)-glycerol (Gly)-polyvinyl alcohol composite hydrogels (PGPHs). The hydrogels exhibited excellent sensing sensitivity with a gauge factor of 2.78, conductivity of 2.2 S/m, tensile deformation of 200%, fast response time of 370 ms, and recovery time of 260 ms, surpassing those of most previously reported hydrogel-based strain sensors. This improvement can be attributed to the high electrical conductivity and uniform distribution of the rGO associated with Gly and PDA. PGPHs also exhibited an attractive monitoring effect for hand movements and precise detection feedback for the slight dynamics of the pharynx. Hydrogel-based strain sensors have been demonstrated as a potentially sustainable solution for dynamic detection and communication.

Phase change materials as a potential passive cooling solution is widely used to cool electronic devices, since the high temperature accompanied by the continuous operation of these electronic devices significantly affects their efficiencies and causes irreversible damage. However, there is a lack of the feedback on cooling potential and recessive failures such as ineffective cooling due to overuse. Here, we report a self-hygroscopic and smart color -changing Co@Li-PAM hydrogel, composed of polyacrylamide (PAM)-based polymer chains, H2O molecules, and functional ions including Li+, Co2+, [Co(H2O)]2+, Cl-, and Br-. It has been found that the hydrophilic porous PAM network acts as the main framework with excellent biocompatibility and reliable chemical stability, LiBr acts as the adsorbent in the PAM network to absorb water molecules in the air during electronic device downtime, and Co ions are introduced into hydrogels through coordination bonds formed with amide groups of polymer chains. The reversible transformation between [Co(H2O)6]2+ and Co2+ driven by the water content in Co@Li-PAM triggers color changes, which indicates the current heat dissipation potential of hydrogels. Applying the as -designed Co@Li-PAM hydrogel to cooling commercial polycrystalline silicon solar cells can increase its energy conversion efficiency by 1.26 % under the illumination of 1 kW m-2. This strategy is expected to provide exotic solutions for the development of electronic devices, carbon neutrality, and global sustainable development goals.

Silicon (Si) is believed to be a promising anode material for lithium-ion batteries (LIBs) and has been intensively studied recently due to its high specific capacity. However, its pulverization induced by the drastic volume change during the lithiation and delithiation processes leads to poor cyclic stability. Graphene has been used as a great potential candidate to solve this problem. Still, the properties of Si and graphene are so different that it is difficult to achieve high-quality contact, which seriously limits the electrochemical performance of Si/graphene composites. Here, we use N-rich gelatin as a carbon source of amorphous carbon to encapsulate Si nanoparticles, which are subsequently anchored and dispersed on graphene. The electrochemical measurements show that the introduction of graphene sheets with suitable size and N-rich amorphous carbon coating on Si nanoparticles could build a more effective charge transfer network compared to conventional carbon coating and simultaneously obtain enhanced mechanical stability, resulting in excellent electrochemical performance. Finally, the Si@AC/G-10 composite (the size of the graphene is ~ 10 μm) anode shows a significantly improved reversible specific capacity of 1192 mAh g-1 after 300 cycles compared to the Si@AC (432 mAh g-1) and bare Si (6 mAh g-1), delivering an effective strategy to enhance the electrochemical performance of anode for application in LIBs.

In energy storage devices, gel polymer electrolytes (GPE) are favorable choices of electrolytes due to the absence of leakage, interchangeability with separators and increased safety compared to liquid electrolytes, and their superior ionic conductivity compared to all-solid electrolytes. However, GPEs' scope of application can be restricted by metrics such as ionic conductivity and operating voltage, while the latter is positively correlated to energy density. Herein, different polymer backbones of GPE and the mechanism of ionic conduction are reviewed. Meanwhile, strategies for enhancing ionic conductivity and energy density of GPE are summarized and discussed through selective presentation of pioneering works. Finally, the current challenges and future directions of GPE research for practical application are encapsulated as an attempt to enlighten ensuing endeavors.

Hydrogel-based evaporators that incorporate photothermal materials with hydrophilic polymer networks have been intensively studied for the promising solar-driven seawater desalination and sewage treatment. However, how to achieve highly-efficient evaporation with both long-term stability and reversible water uptake has always been a significant challenge. Herein, a durable and rechargeable solar evaporator is demonstrated by integrating water-absorbing polyacrylamide hydrogels with light-harvesting carbon nanotubes through polymerization in freeze-drying process. The hydrogel can store water 6 times its own weight. Even after being stored for 150 days, it can also restore its original shape after recharge by swelling in water. The hydratable functional groups endow the hydrogel with the formation of intermediate water that has a weak hydrogen bond, leading to reduced evaporation enthalpy. Without additional water supply, 2D flat evaporator with the hydrogel shows an evaporation rate of 3.03 kg m(-2) h(-1) under one sun irradiation. Further benefiting from net energy gain from the environment, a high and stable evaporation rate of 4.85 kg m(-2) h(-1) under one sun irradiation can be realized using 3D cylindrical hydrogel. This rechargeable hydrogel can be easily recycled via swelling-evaporation, with outstanding evaporation rate that qualifies for long-term use, making it ideal for practical clean water production.

The thriving solar-driven water evaporation (SDWE) technology is considered the ideal candidate for next-generation water treatment because of its high efficiency, environment-friendliness, and low cost. The irresistible trend of diversified energy demand presents multi-functional requirements for a successful SWDE. However, the current SDWE technology rarely breaks through this technical dilemma. Here, we have designed a bifunctional polypyrrole-based capacitor to achieve water purification and energy storage. The hydrophilicity of the filter paper and the high light absorptance of polypyrrole (96.18%) promote the generation of solar steam. The evaporation rate of the PPy-200 (Polypyrrole-200) filter paper reached 1.54 kg m-2 h-1 under 1 kW m-2. Interestingly, the symmetric supercapacitor assembled with PPy-based filter paper electrodes could simultaneously realize efficient evaporation (1.94 kg m-2 h-1) and electrochemical energy storage. As a single electrode, the PPy-200 filter paper exhibited ultra-high specific capacitance (4129.50 mF cm-2) and favorable cycling stability (71.16% after 4000 cycles). More importantly, the capacitance of PP-PPy-200 (Polyvinyl alcohol/Polyethylene glycol-Polypyrrole-200) increased to 2.55 times under one sun illumination. This work not only points out a direction for solar thermal utilization, but also provides new design inspiration for high-efficiency flexible electrochemical energy storage devices.

Freshwater generation by solar distillation is a promising technology to relieve global water scarcity. However, the evaporation of water requires a lot of energy, and the fragile purifier is easily damaged, resulting in low water production in practical applications. Therefore, a material simultaneously possessing low water evaporation enthalpy and strong toughness is desired. Herein, the authors introduced agar into polyacrylamide (AP) to uniquely design hydroxyl group ramparts on the skeleton of hydrogel to uniquely design hydroxyl groups rampart on the skeleton of hydrogel to strengthen robustness of hydrogel and regulate water state, which not only reduces energy demand for evaporation but resists external disturbance. The tensile stress of CNT 100 ‐AP 1/9 hydrogel reaches the maximum value of 102 kPa while the tensile strain is 467%. Finally, a high evaporation rate of ≈3 kg m −2 h −1 with 86.2% photothermal conversion efficiency is obtained under 1 kW m −2 illumination. The ingenious structure to wear hydroxyl groups coat on the skeleton of PAM hydrogel opens a new avenue for building a new robust and efficient solar thermal desalination system.

An effective thermoelectricity–freshwater cogenerator using solar energy and scavenging energy has been proposed as a promising solution to water scarcity and electricity shortage.

Spinel ferrite, with the characteristics of multiple oxidation states, good electrochemical stability, and excellent light absorption properties, shows great potential as an energy storage electrode and photothermal conversion material. Thereby, bifunctional material based on NiFe2O4 spinel ferrite in supercapacitor and solar steam generation is proposed for the first time in this work. NiFe2O4-NiAl-LDH-ACC, the composite with hollow and layered nanosheet structures was prepared by hydrothermal growth of NiAl-layered double hydroxide (NiAl-LDH) on the surface of activated carbon cloth (ACC) as well as NiFe2O4. The uniform growth of NiAl-LDH on the surfaces of ACC and NiFe2O4 further improves the overall structural stability, and the synergy effect between different metal compounds enhances the electrochemical and conductivity performance of the composites. Furthermore, ACC, as a photothermal conversion material, shows benign light absorption and hydrophilicity, which further enables the composite material to obtain high solar vapor generation rate by combining with NiFe2O4. As a result, NiFe2O4-NiAl-LDH-ACC composite display an eminent specific capacitance (2015 F g-1 at 1 A g-1) and a favorable evaporation rate (1.73 kg m- 2 h-1 under 1 kW m-2). In addition, the asymmetric supercapacitor with NiFe2O4-NiAl-LDH-ACC as the positive electrode and activated carbon (AC) as the negative electrode present excellent energy density (72.2 Wh kg- 1 at 830.2 W kg -1) and outstanding cycling stability (85.5% retention after 10,000 cycles). In the era of energy scarcity when single functional materials cannot satisfy applications in multiple scenarios and development faces limitations, it is obvious that NiFe2O4-NiAl-LDH-ACC, as a bifunctional material, provides vital design inspiration and enlightenment for both energy storage and photothermal conversion.

Abstract In recent years, pursuing a high evaporation rate of solar steam generation (SSG) has been the focus of research for relieving the freshwater shortage. Scientists struggled to find perfect photothermal materials while the importance of substrate during the steam generation was often overlooked. Therefore, in this work, an aerogel substrate composed of polyvinyl alcohol (PVA) and chitosan (CS) has been designed for solar steam generation. The compounded aerogels synthesized via freeze‐drying method not only retain the inherent characteristics of lightweight, porosity, and high specific surface area, but also inherit the advantages of PVA in water lock effect as well as CS in moisture absorption. The obtained PVA/CS/CuO aerogel coupling with high light absorption of CuO exhibited excellent steam generation capabilities, largely benefited from the superiority of the aerogel substrate. Under 1 sun solar illumination (1 kW m–2), it realized an evaporation rate as high as 2.14 Kg m–2 h–1, which is superior to recently reported semiconductor solar evaporation system. The solar‐to‐vapor energy conversion efficiency of 87.1% is obtained. Due to the versatility of CuO, PVA/CS/CuO aerogel not only has excellent light‐to‐heat conversion performance, but also has good effects in antibacterial.