Underwater Self‐Cleaning PEDOT‐PSS Hydrogel Mesh for Effective Separation of Corrosive and Hot Oil/Water Mixtures

Oil‐polluted water is a worldwide problem due to the increasing industry oily wastewater and the frequent oil‐spill pollution. Here, PEDOT‐PSS hydrogel meshes are successfully prepared by using in‐situ chemical polymerization on Ti mesh substrate, which are composed of hierarchical porous structures and present superhydrophilicity in air and superoleophobicity underwater. And PEDOT‐PSS hydrogel meshes exhibit excellent environmental stability under a series of harsh conditions, which are used for the separation of the mixtures of oil and various corrosive and active aqueous solutions, including strong acidic, alkaline, or salt aqueous solutions, even hot‐water. The hydrogel meshes offer high separation efficiency of up to 99.9%. Importantly, the mesh still reveals 99.5% separation efficiency even after 50 times separation operation, demonstrating its excellent durability that shows attractive potential for practical oil‐water separation in industry and everyday life.     

Facile Fabrication of Eco‐Friendly Durable Superhydrophobic Material from Eggshell with Oil/Water Separation Property

Most superhydrophobic surfaces are fragile and even lose their functions under harsh conditions especially in outdoor applications. In this study, we have demonstrated a facile strategy for fabricating eco‐friendly and mechanical durable superhydrophobic material from eggshell. The as‐prepared superhydrophobic materials possess not only excellent self‐cleaning property and under oil superhydrophobicity, but also high‐efficient oil/water separation capability. More importantly, the obtained materials show outstanding and mechanical durable water repellency, which can maintain superhydrophobicity after 360 cm abrasion length of sandpaper. In addition, the materials also show durable superhydrophobic toward strong acidic/alkali solutions, UV irradiation, and water droplet impact, which demonstrates the outstanding chemical and environmental stability. This facile fabrication of the mechanical durable superhydrophobic materials and the utilization of daily garbage will provide the new ideas for engineering materials and accelerate the real application of the super‐repellent materials.

     

Barrel‐Shaped Oil Skimmer Designed for Collection of Oil from Spills

Superhydrophobic–superoleophilic (SS) materials have the prospect to be used in oil‐spill cleanup as treated felts because of their complete oil‐absorbing and water‐repelling properties. The main issues affecting the practical application of the SS materials are the low volume‐based absorption capacity (resulting in a high cost), the requirement for mechanical handling (squeeze out the oil) for recycling, and low storage stability of the collected oil. In this study, a barrel‐shaped oil skimmer mainly composed of an SS Cu foam and a glass barrel is developed as a potential step‐change device to enable separation of oil and water. The SS Cu active component is fabricated by chemical etching and stearic acid modification. The demonstrator oil skimmer quickly and selectively absorbs and collects a variety of oils from a polluted water surface, showing a high separation efficiency and volume‐based absorption capacity. The device can be easily scaled up. In addition to the high absorption capacity, the as‐prepared oil skimmer filters and collects the floating oil into the barrel, removing the traditional mechanical handling. Moreover, the as‐prepared oil skimmer also shows good storage stability; no oil escapes from the skimmer under harsh conditions. The findings presented in this study facilitate a novel, simple, and low‐cost approach for oil‐spill cleanup.     

Facile preparation of super-hydrophobic nanofibrous membrane for oil/water separation in a harsh environment

Oil removal or oil/water separation from the industrial waste water especially under harsh environment such as acid and alkali solutions have now been becoming an urgent task for human being. Here, flexible nanofibrous membrane with super-hydrophobicity/super-oleophilicity was prepared through a facile one-step solution-immersion approach, i.e., the poly(vinylidene fluoride) nanofiber mat modified with methyltrichlorosilane (MTS). The nanostructured polysiloxane with different morphologies including the ultrathin cylindrical wires and particles, were present on the nanofiber surface after MTS hydrolysis and subsequent condensation, which significantly enhanced the surface roughness and hence the hydrophobicity of the membrane. The influence of MTS concentration in the n-hexane solution and the hydrolysis time of MTS on the morphology of polysiloxane decorated nanofiber and hence the super-hydrophobicity was investigated in detail. The super-hydrophobic nanofibrous membrane could repel hot water and corrosive solutions, and the contact angle maintained around 150° with a pH ranging from 1 to 13. It was found that the oil/water separation with a high flux and efficiency was achieved by using the nanofibrous membrane that could not only separate the oil with the pure water and hot water but also the corrosive solution including the salt, acid and alkali solution. The organic/inorganic hybrid nanofibrous membrane may have find its potential applications in oil/water separation under a harsh environment.     

Robust Flower‐Like TiO2@Cotton Fabrics with Special Wettability for Effective Self‐Cleaning and Versatile Oil/Water Separation

Inspired by the hierarchical structure of the mastoid on the micrometer and nanometer scale and the waxy crystals of the mastoid on natural lotus surfaces, a facile one‐step hydrothermal strategy is developed to coat flower‐like hierarchical TiO₂ micro/nanoparticles onto cotton fabric substrates (TiO₂@Cotton). Furthermore, robust superhydrophobic TiO₂@Cotton surfaces are constructed by the combination of hierarchical structure creation and low surface energy material modification, which allows versatility for self‐cleaning, laundering durability, and oil/water separation. Compared with hydrophobic cotton fabric, the TiO₂@Cotton exhibits a superior antiwetting and self‐cleaning property with a contact angle (CA) lager than 160° and a sliding angle lower than 5°. The superhydrophobic TiO₂@Cotton shows excellent laundering durability against mechanical abrasion without an apparent reduction of the water contact angle. Moreover, the micro/nanoscale hierarchical structured cotton fabrics with special wettability are demonstrated to selectively collect oil from oil/water mixtures efficiently under various conditions (e.g., floating oil layer or underwater oil droplet or even oil/water mixtures). In addition, it is expected that this facile strategy can be widely used to construct multifunctional fabrics with excellent self‐cleaning, laundering durability, and oil/water separation. The work would also be helpful to design and develop new underwater superoleophobic/superoleophilic materials and microfluidic management devices.     

Sprayable and rapidly bondable phenolic-metal coating for versatile oil/water separation

Phenolic-metal complexation coatings have been discovered to be a universal route for the deposition of multifunctional coatings. However, most complexation coatings have been prepared by the immersion method, which limits their practical large-scale application. Herein, we describe a facile and green engineering strategy that involves spraying phenolic compound and metal ions on substrate to form in-situ complexation coating with different coordination states. The coating is formed within minutes and it can be achieved in large scale by the spray method. The pyrogallol-Fem complexation coating is prepared at pH 7.5, which consists predominantly of biscoordination complexation with a small amount of tris-coordination complexation. It displays that the water contact angle is near zero due to the generation of rough hierarchical structures and massive hydroxyl groups. The superhydrophilic cotton resulting from the deposition of the pyrogallol-Fe^Ⅲ complexation can separate oil/water mixtures and surfactant-stabilized oil-in-water emulsions with high separation efficiency. The formation of the phenolic-metal complexation coating by using spray technique constitutes a cost-effective and environmentally friendly, strategy with potential to be applied for large-scale surface engineering processes and green oil/water separation.     

Dual‐Layer Superamphiphobic/Superhydrophobic‐Oleophilic Nanofibrous Membranes with Unidirectional Oil‐Transport Ability and Strengthened Oil–Water Separation Performance

Thin porous membranes with unidirectional oil‐transport capacity offer great opportunities for intelligent manipulation of oil fluids and development of advanced membrane technologies. However, directional oil‐transport membranes and their unique membrane properties have seldom been reported in research literature. Here, it is proven that a dual‐layer nanofibrous membrane comprising a layer of superamphiphobic nanofibers and a layer of superhydrophobic oleophilic nanofibers has an unexpected directional oil‐transport ability, but is highly superhydrophobic to liquid water. This novel fibrous membrane is prepared by a layered electrospinning technique using poly(vinylidene fluoride‐hexafluoropropylene) (PVDF‐HFP), PVDP‐HFP containing well‐dispersed FD‐POSS (fluorinated decyl polyhedral oligomeric silsesquioxanes), and FAS (fluorinated alkyl silane) as materials. The directional oil‐transport is selective only to oil fluids with a surface tension in the range of 23.8–34.0 mN m^–1. By using a mixture of diesel and water, it is further proven that this dual‐layer nanofibrous membrane has a higher diesel–water separation ability than the single‐layer nanofiber membranes. This novel nanofibrous membrane and the incredible oil‐transport ability may lead to the development of intelligent membrane materials and advanced oil–water separation technologies for diverse applications in daily life and industry.     

An Oxidative Enzyme Boosting Mechanical and Optical Performance of Densified Wood Films

Nature has evolved elegant ways to alter the wood cell wall structure through carbohydrate-active enzymes, offering environmentally friendly solutions to tailor the microstructure of wood for high-performance materials. In this work, the cell wall structure of delignified wood is modified under mild reaction conditions using an oxidative enzyme, lytic polysaccharide monooxygenase (LPMO). LPMO oxidation results in nanofibrillation of cellulose microfibril bundles inside the wood cell wall, allowing densification of delignified wood under ambient conditions and low pressure into transparent anisotropic films. The enzymatic nanofibrillation facilitates microfibril fusion and enhances the adhesion between the adjacent wood fiber cells during densification process, thereby significantly improving the mechanical performance of the films in both longitudinal and transverse directions. These results improve the understanding of LPMO-induced microstructural changes in wood and offer an environmentally friendly alternative for harsh chemical treatments and energy-intensive densification processes thus representing a significant advance in sustainable production of high-performance wood-derived materials.     

Multifunction ZnO/carbon hybrid nanofiber mats for organic dyes treatment via photocatalysis with enhanced solar-driven evaporation

ZnO-based photocatalytic materials have received widespread attention due to their usefulness than other photocatalytic materials in organic dye wastewater treatment. However, its photocatalytic efficiency and surface stability limit further applicability. This paper uses a one-step carbonization method to prepare multifunctional ZnO/carbon hybrid nanofiber mats. The carbonization creates a π-conjugated carbonaceous structure of the mats, which prolongs the electron recovery time of ZnO nanoparticles to yield improved photocatalytic efficiency. Further, the carbonization reduces the fiber diameter of the carbon hybrid nanofiber mats, which quadruples the specific surface area to yield enhanced adsorption and photocatalytic performance. At the same time, the prepared nanofiber mats can increase the evaporation rate of water under solar irradiation to a level of 1.46 kg·m⁻²·h⁻¹ with an efficiency of 91.9%. Thus, the nanofiber mats allow the facile incorporation of photocatalysts to clean contaminated water through adsorption, photodegradation, and interfacial heat-assisted distillation mechanisms.     

Robust fabrication of fluorine-free superhydrophobic steel mesh for efficient oil/water separation

A facile and environmentally friendly method was reported for the fabrication of superhydrophobic steel mesh by depositing with dual-scale Polystyrene@Silica (PS@SiO₂) particles coated with hexadecyltrimethoxysilane (HDTMS), which provided 3D multi-scale hierarchical rough surface structure with low surface energy to perform the superhydrophobic effect. PS particles of ~1 μm and ~200 nm were first synthesized via dispersion polymerization and emulsion polymerization, respectively. The obtained PS particles were then used as template for the silification using tetraethyl orthosilicate as the precursor. After treated with HDTMS, the PS@SiO₂ particles were deposited on steel mesh forming dual-sized hierarchical structures. The as-prepared film exhibited excellent water repellence with a water contact angle of 161.6° ± 1.1° and water contact angle hysteresis of 3.4°. It also showed efficient and rapid oil/water separation ability and could be repeatedly used for at least 5 times. This facile synthesis strategy for fabricating multifunctional steel mesh provides potential applications in large-scale oil–water separation.     

Toward Environmentally Robust Organic Electronics: Approaches and Applications

Recent interest in flexible electronics has led to a paradigm shift in consumer electronics, and the emergent development of stretchable and wearable electronics is opening a new spectrum of ubiquitous applications for electronics. Organic electronic materials, such as π‐conjugated small molecules and polymers, are highly suitable for use in low‐cost wearable electronic devices, and their charge‐carrier mobilities have now exceeded that of amorphous silicon. However, their commercialization is minimal, mainly because of weaknesses in terms of operational stability, long‐term stability under ambient conditions, and chemical stability related to fabrication processes. Recently, however, many attempts have been made to overcome such instabilities of organic electronic materials. Here, an overview is provided of the strategies developed for environmentally robust organic electronics to overcome the detrimental effects of various critical factors such as oxygen, water, chemicals, heat, and light. Additionally, molecular design approaches to π‐conjugated small molecules and polymers that are highly stable under ambient and harsh conditions are explored; such materials will circumvent the need for encapsulation and provide a greater degree of freedom using simple solution‐based device‐fabrication techniques. Applications that are made possible through these strategies are highlighted.     

Twofold bioinspiration of TiO2-PDA hybrid fabrics with desirable robustness and remarkable polar/nonpolar liquid separation performance

The fundamental relationship between microstructure,constituent,processing and performances of separating materials is really a vital issue.Traditional preparation methods for separation membranes are complex,time-consuming and easy to be fouled.Also,the durability of conventional coatings on membrane is poor.By combination of bioinspiration from mussel adhesive and fish scales’underwater superoleophobicity,we propose a general route to prepare organic-inorganic hybrid coatings,while no complex apparatus is needed.Specifically,based on the biomimetic adhesion of polydopamine(PDA),we used it as a binder to adhere TiO₂nanoparticles and built rough microstructure on fabric.In this way,we obtained TiO₂-PDA treated fabric with special wettability.These TiO₂-PDA treated samples owned superamphiphilicity in air,underwater superoleophobicity(underwater oil contact angles(OCAs)>150°),underoil superhydrophobicity(underoil water contact angles(WCAs)>150°),excellent multiresistance;and can separate polar/nonpolar liquid mixture effectively.It also owned superaerophobicity underwater(underwater bubble contact angles(BCAs)>150°).The proposed TiO₂-PDA coatings are highly expected to be employed for real situation of water pollution remediation,self-cleaning,oil extraction and harsh chemical engineering issues.     

Current Status and Future Prospects of Metal–Sulfur Batteries

Lithium–sulfur batteries are a major focus of academic and industrial energy‐storage research due to their high theoretical energy density and the use of low‐cost materials. The high energy density results from the conversion mechanism that lithium–sulfur cells utilize. The sulfur cathode, being naturally abundant and environmentally friendly, makes lithium–sulfur batteries a potential next‐generation energy‐storage technology. The current state of the research indicates that lithium–sulfur cells are now at the point of transitioning from laboratory‐scale devices to a more practical energy‐storage application. Based on similar electrochemical conversion reactions, the low‐cost sulfur cathode can be coupled with a wide range of metallic anodes, such as sodium, potassium, magnesium, calcium, and aluminum. These new “metal–sulfur” systems exhibit great potential in either lowering the production cost or producing high energy density. Inspired by the rapid development of lithium–sulfur batteries and the prospect of metal–sulfur cells, here, over 450 research articles are summarized to analyze the research progress and explore the electrochemical characteristics, cell‐assembly parameters, cell‐testing conditions, and materials design. In addition to highlighting the current research progress, the possible future areas of research which are needed to bring conversion‐type lithium–sulfur and other metal–sulfur batteries into the market are also discussed.     

Antifouling on Gecko's Feet Inspired Fibrillar Surfaces: Evolving from Land to Marine and from Liquid Repellency to Algae Resistance

In nature, biological creatures (including plants and animals) have self‐cleaning capability despite the vagaries of the environment, i.e., from sky to land, and then to marine and vagaries of foulants (non‐living and living). Gecko's feet have the general self‐cleaning property both in air and underwater so as to keep their feet all clean for traveling through changing their adhesion. The present work reports Gecko's fibrillar structures to demonstrate general antifouling property in air through hydrophobicity and underwater after modification with hydrophilic polymer brushes. Fibrillar polypropylene (PP) nanoarrays are fabricated by hot embossing, exhibiting superhydrophobic antifouling in air. By grafting hydrophilic polyelectrolyte brushes (PSPMA) via surface‐initiated atom transfer radical polymerization, they show superoleophobic antifouling of oil droplet and algae adhesion underwater. The effect of the structure of PP nanofiber arrays on the wettability and adhesion behavior is evaluated in detail. The results provide an important scientific principle for fabricating self‐cleaning low‐fouling materials with micro/nanostructure, with the hydrophobic ones being more applicable in air and the hydrophilic ones well suited underwater.     

Underwater Mechanically Robust Oil‐Repellent Materials: Combining Conflicting Properties Using a Heterostructure

The development of underwater mechanically robust oil‐repellent materials is important due to the high demand for these materials with the increase in underwater activities. Based on the previous study, a new strategy is demonstrated to prepare underwater mechanically robust oil‐repellent materials by combining conflicting properties using a heterostructure, which has a layered hydrophobic interior structure with a columnar hierarchical micro/nanostructure on the surface and a hydrophilic outer structure. The surface hydrophilic layer imparts underwater superoleophobicity and low oil adhesion to the material, which has oil contact angle of larger than 150° and adhesion of lower than 2.8 µN. The stability of the mechanical properties stemming from the interior hydrophobic‐layered structure enables the material to withstand high weight loads underwater. The tensile stress and the hardness of such a heterostructure film after 1 month immersion in seawater and pH solution are in the range from 83.92 ± 8.22 to 86.73 ± 7.8 MPa and from 83.88 ± 6.8 to 86.82 ± 5.64 MPa, respectively, which are superior to any underwater oil‐repellent material currently reported.     

Zeolite (In)Stability under Aqueous or Steaming Conditions

Zeolites are among the most environmentally friendly materials produced industrially at the Megaton scale. They find numerous commercial applications, particularly in catalysis, adsorption, and separation. Under ambient conditions aluminosilicate zeolites are stable when exposed to water or water vapor. However, at extreme conditions as high temperature, high water vapor pressure or increased acidity/basicity, their crystalline framework can be destroyed. The stability of the zeolite framework under aqueous conditions also depends on the concentration and character of heteroatoms (other than Al) and the topology of the zeolite. The factors critical for zeolite (in)stability in the presence of water under various conditions are reviewed from the experimental as well as computational sides. Nonreactive and reactive interactions of water with zeolites are addressed. The goal of this review is to provide a comparative overview of all-silica zeolites, aluminosilicates and zeolites with other heteroatoms (Ti, Sn, and Ge) when contacted with water. Due attention is also devoted to the situation when partial zeolite hydrolysis is used beneficially, such as the formation of hierarchical zeolites, synthesis of new zeolites or fine-tuning catalytic or adsorption characteristics of zeolites.     

Cl‐Doped ZnO Nanowire Arrays on 3D Graphene Foam with Highly Efficient Field Emission and Photocatalytic Properties

An environmentally friendly, low‐cost, and large‐scale method is developed for fabrication of Cl‐doped ZnO nanowire arrays (NWAs) on 3D graphene foam (Cl‐ZnO NWAs/GF), and investigates its applications as a highly efficient field emitter and photocatalyst. The introduction of Cl‐dopant in ZnO increases free electrons in the conduction band of ZnO and also leads to the rough surface of ZnO NWAs, which greatly improves the field emission properties of the Cl‐ZnO NWAs/GF. The Cl‐ZnO NWAs/GF demonstrates a low turn‐on field (≈1.6 V μm⁻¹), a high field enhancement factor (≈12844), and excellent field emission stability. Also, the Cl‐ZnO NWAs/GF shows high photocatalytic efficiency under UV irradiation, enabling photodegradation of organic dyes such as RhB within ≈75 min, with excellent recyclability. The excellent photocatalytic performance of the Cl‐ZnO NWAs/GF originates from the highly efficient charge separation efficiency at the heterointerface of Cl‐ZnO and GF, as well as improved electron transport efficiency due to the doping of Cl. These results open up new possibilities of using Cl‐ZnO and graphene‐based hybrid nanostructures for various functional devices.     

Bubble‐Enabled Underwater Motion of a Light‐Driven Motor

This work reports the photothermally driven horizontal motion of a motor as well as the suspending and vertical movements underwater. A motor is designed by attaching two polydimethylsiloxane‐coated oxidized copper foams (POCF) to the two opposite sides of an oxidized copper foam (OCF). When the hydrophobic POCF is immersed in water, it serves as both an air bubble trapper and a light‐to‐heat conversion center. As bubbles grow under photothermal heating, they provide lifting force and result in the revolving motion of the motor. With removal of light illumination, bubbles are cooled by the surrounding water and shrink, and the buoyance is lowered. The resultant force of gravitational force, buoyance, and fluid resistance drives the motor to move forward horizontally. Furthermore, the motors are utilized as oil collectors and oil/water separation is achieved successfully. To effectively control the suspending motion, a polydimethylsiloxane foam doped with carbon black (C‐foam) is designed under the photothermal principle. It is maintained at a certain position underwater by controlling the on/off of light. The vertical motion is also studied and utilized to generate electricity. It is expected that different types of underwater motion will open up new opportunities for various applications including drug delivery, collection of heavy oil underwater, and electricity generation.     

Ultralight Multifunctional Carbon‐Based Aerogels by Combining Graphene Oxide and Bacterial Cellulose

Nanostructured carbon aerogels with outstanding physicochemical properties have exhibited great application potentials in widespread fields and therefore attracted extensive attentions recently. It is still a challenge so far to develop flexible and economical routes to fabricate high‐performance nanocarbon aerogels, preferably based on renewable resources. Here, ultralight and multifunctional reduced graphene oxide/carbon nanofiber (RGO/CNF) aerogels are fabricated from graphene oxide and low‐cost, industrially produced bacterial cellulose by a three‐step process of freeze‐casting, freeze‐drying, and pyrolysis. The prepared RGO/CNF aerogel possesses a very low apparent density in the range of 0.7–10.2 mg cm^?3 and a high porosity up to 99%, as well as a mechanically robust and electrically conductive 3D network structure, which makes it to be an excellent candidate as absorber for oil clean‐up and an ideal platform for constructing flexible and stretchable conductors.