Valence electronic engineering of superhydrophilic Dy-evoked Ni-MOF outperforming RuO_(2) for highly efficient electrocatalytic oxygen evolution

Tackling the problem of poor conductivity and catalytic stability of pristine metal-organic frameworks(MOFs) is crucial to improve their oxygen evolution reaction(OER) performance.Herein,we introduce a novel strategy of dysprosium(Dy) doping,using the unique 4f orbitals of this rare earth element to enhance electrocatalytic activity of MOFs.Our method involves constructing Dy-doped Ni-MOF(Dy@Ni-MOF) nanoneedles on carbon cloth via a Dy-induced valence electronic perturbation approach.Experiments and density functional theory(DFT) calculations reveal that Dy doping can effectively modify the electronic structure of the Ni active centers and foster a strong electronic interaction between Ni and Dy.The resulting benefits include a reduced work function and a closer proximity of the d-band center to the Fermi level,which is conducive to improving electrical conductivity and promoting the adsorption of oxygen-containing intermediates.Furthermore,the Dy@Ni-MOF achieves superhydrophilicity,ensuring effective electrolyte contact and thus accelerating reaction kinetics,Ex-situ and in-situ analysis results manifest Dy_(2)O_(3)/NiOOH as the actual active species.Therefore,Dy@Ni-MOF shows impressive OER performance,significantly surpassing Ni-MOF.Besides,the overall water splitting device with Dy@NiMOF as an anode delivers a low cell voltage of 1.51 V at 10 mA cm^(-2) and demonstrates long-term stability for 100 h,positioning it as a promising substitute for precious metal catalysts.

Hierarchically wood-derived integrated electrode with tunable superhydrophilic/superaerophobic surface for efficient urea electrolysis

Conferring surfaces with superhydrophilic/superaerophobic characteristics is desirable for synthesizing efficient gas reaction catalysts.However,complicated procedures,high costs,and poor interfaces hinder commercialization.Here,an integrated electrode with tunable wettability derived from a hierarchically porous wood scaffold was well designed for urea oxidation reaction(UOR).Interestingly,the outer surface of the wood lumen was optimized to the preferred wettability via stoichiometry to promote electrolyte permeation and gas escape.This catalyst exhibits outstanding activity and durability for UOR in alkaline media,requiring only a potential of 1.36 V(vs.RHE)to deliver 10 m A cm^(-2)and maintain its activity without significant decay for 60 h.These experiments and theoretical calculations demonstrate that the nickel(oxy)hydroxide layer formed through surface reconstruction of nickel nanoparticles improves the active sites and intrinsic activity.Moreover,the superwetting properties of the electrode promote mass transfer by guaranteeing substantial contact with the electrolyte and accelerating the separation of gaseous products during electrocatalysis.These findings provide the understanding needed to manipulate the surface wettability through rational design and fabrication of efficient electrocatalysts for gas-evolving processes.

Fully Superhydrophilic, Self-Floatable, and Multi-Contamination-Resistant Solar Steam Generator Inspired by Seaweed

Highly hydrophilic materials enable rapid water delivery and salt redissolution in solar-driven seawater desalination. However, the lack of independent floatability inhibits heat localization at the air/water interface. In nature, seaweeds with internal gas microvesicles can float near the sea surface to ensure photosynthesis. Here, we have developed a seaweed-inspired, independently floatable, but superhydrophilic (SIFS) solar evaporator. It needs no extra floatation support and can simultaneously achieve continuous water pumping and heat concentration. The evaporator resists salt accumulation, oil pollution, microbial corrosion, and protein adsorption. Densely packed hollow glass microbeads promote intrinsic floatability and heat insulation. Superhydrophilic zwitterionic sulfobetaine hydrogel provides a continuous water supply, redissolves the deposited salt, and endows the SIFS evaporator with excellent anti-fouling properties. With its unprecedented anti-contamination ability, this SIFS evaporator is expected to open a new avenue for designing floatable superhydrophilic materials and solving real-world issues of solar steam generation in complex environmental conditions.

Superhydrophilic–superhydrophobic patterned surfaces:From simplified fabrication to emerging applications

Superhydrophilic–superhydrophobic patterned surfaces constitute a branch of surface chemistry involving the two extreme states of superhydrophilicity and superhydrophobicity combined on the same surface in precise patterns.Such surfaces have many advantages,including controllable wettability,enrichment ability,accessibility,and the ability to manipulate and pattern water droplets,and they offer new functionalities and possibilities for a wide variety of emerging applications,such as microarrays,biomedical assays,microfluidics,and environmental protection.This review presents the basic theory,simplified fabrication,and emerging applications of superhydrophilic–superhydrophobic patterned surfaces.First,the fundamental theories of wettability that explain the spreading of a droplet on a solid surface are described.Then,the fabrication methods for preparing superhydrophilic–superhydrophobic patterned surfaces are introduced,and the emerging applications of such surfaces that are currently being explored are highlighted.Finally,the remaining challenges of constructing such surfaces and future applications that would benefit from their use are discussed.

Osteoconductivity of Superhydrophilic Anodized TiO₂Coatings on Ti Treated with Hydrothermal Processes

Surface hydrophilicity is considered to have a strong influence on the biological reactions of bone-substituting materials. However, the influence of a hydrophilic surface on osteoconductivity is not completely clear, especially for superhydrophilic surfaces. In this study, we conferred superhydrophilic properties on anodized TiO2 coatings using a hydrothermal treatment, and developed a method to maintain this surface until implantation. The osteoconductivity of these coatings was evaluated with in vivo tests. A hydrothermal treatment made the surface of as-anodized samples more hydrophilic, up to a water contact angle of 13 (deg.). Storage in both air and distilled water increased the water contact angle after several days because of the adsorption of hydrocarbon. However, storage in phosphate buffered solution led to a reduction in the water contact angle, because of the adsorption of the inorganic ions in the solution, and the sample retained its high hydrophilicity for a long time. As the water contact angle decreased, the hard tissue formation ratio increased continuously up to 58%, which was about four times higher than the hard tissue formation ratio on as-polished Ti.

Wettability Control between Oleophobic/Superhydrophilic and Superoleophilic/Superhydrophobic Characteristics on the Modified Surface Treated with Fluoroalkyl End-Capped Oligomers/Micro-Sized Polystyrene Particle Composites

Fluoroalkyl end-capped vinyltrimethoxysilane-N,N-dimethylacrylamide cooligomer [RF-(CH2-CHSi(OMe)3)x-(CH2-CHC(=O)NMe2)y-RF;RF = CF(CF3)OC3F7: RF-(VM)x-(DMAA)y-RF] was synthesized by reaction of fluoroalkanoyl peroxide [RF-C(=O)O-O(O=)C-RF] with vinyltrimethoxysilane (VM) and N,N-dimethylacrylamide (DMAA). The modified glass surface treated with the cooligomeric nanoparticles [RF-(VM-SiO3/2)x-(DMAA)y-RF] prepared under the sol-gel reaction of the cooligomer under alkaline conditions was found to exhibit an oleophobic/superhydrophilic property, although the corresponding fluorinated homooligomeric nanoparticles [RF-(VM-SiO3/2)n-RF] afforded an oleophobic/hydrophobic property on the modified surface under similar conditions. RF-(VM-SiO3/2)n-RF/RF-(VM-SiO3/2)x-(DMAA)y-RF/PSt (micro-sized polystyrene particles) composites, which were prepared by the sol-gel reactions of the corresponding homooligomer and cooligomer in the presence of PSt particle under alkaline conditions, provided an oleophobic/superhydrophilic property on the modified surface. However, it was demonstrated that the surface wettability on the modified surface treated with the RF-(VM-SiO3/2)n-RF/RF-(VM-SiO3/2)x-(DMAA)y-RF/PSt composites changes dramatically from oleophobic/superhydrophilic to superoleophilic/superhydrophilic and superoleophilic/superhydrophobic characteristics, increasing with greater feed ratios (mg/mg) of the RF-(VM)n-RF homooligomer in homooligomer/cooligomer from 0 to 100 in the preparation of the composites. Such controlled surfac

Superhydrophilic nickel hydroxide ultrathin nanosheets enable high-performance asymmetric supercapacitors

Superhydrophilic surfaces have been applied for supercapacitor;however,during energy storage reaction,how the wettability affects the process of electrochemical reaction specifically is still unclear.Herein,we demonstrate superhydrophilic surface for promotion of electrochemical reactions by liquid affinity and further explain the mechanism,where the transition of the wettability state caused by the change in surface free energy is the main reason for the obvious increase in specific capacitance.Through citric acid assistance strategy,an intrinsically hydrophobic Ni(OH)_(2)thick nanosheets(HNHTNs,16 nm)can be transitioned into superhydrophilic Ni(OH)_(2)ultrathin nanosheets(SNHUNs,6.8 nm),where the water contact angle was 0°and the surface free energy increased from 8.6to 65.8 mN·m^(-1),implying superhydrophilicity.Compared with HNHTNs,the specific capacitance of SNHUNs is doubled:from 1230 F·g^(-1)(HNHTNs)to 2350 F·g^(-1)(2A·g^(-1))and,even at 20 A·g^(-1),from 833 F·g^(-1)(HNHTNs)to 1670 F·g^(-1).The asymmetric capacitors assembled by SNHUNs and activated carbon show 52.44 Wh·kg^(-1)at 160W·kg^(-1)and excellent stability with~90%retention after5000 cycles(~80%retention after 9500 cycles).The promotion of electrochemical performances is ascribed to the change of surface wettability caused by surface free energy,which greatly increase affinity of electrode to the surrounding liquid environment to reduce the interface resistance and optimize the electron transport path.

Superhydrophilic membrane with photo-Fenton self-cleaning property for effective microalgae anti-fouling

Membrane filtration is one of the effective approaches to harvest microalgae for industrial biofuel production.However,during the filtration process,microalgae cells and extracellular organic matter(EOM)will deposit on the membrane surface leading to reversible membrane fouling that can be removed by physical methods.When hydrophobic EOM is adsorbed on the membrane surface or inside pores,it will build up a gel layer,causing irreversible membrane fouling.Irreversible fouling can only be removed using chemical methods that will decrease membrane lifespan and increase operational costs.Here,we introduce a versatile superhydrophilic membrane with photo-Fenton self-cleaning property,which can prevent the reversible fouling and remove the irreversible fouling.Tannic acid(TA)and 3-aminopropyltriethoxysilane(APTES)were co-deposited on the polyvinylidene fluoride(PVDF)membrane via Schiff base and Michael addition reactions,andβ-FeOOH nanorods were inlaid on the membrane surface by in situ mineralization.The water contact angle of the modified membrane is reduced from 120°to 0°Under 60 min visible light,the hydroxyl radical(·OH)generated by the photo-Fenton reaction degraded the irreversible fouling that blocked membrane pores.The irreversible fouling rates of modified membrane was reduced from 39.57%to 3.26%,compared with the original membrane.Microalgae harvesting results illustrated that the membrane has a high flux recovery rate(FRR)of 98.2%,showed excellent passive antifouling and active antifouling performance.We believe this work will spark a novel platform for optimizing energy-efficient microalgae harvesting separation membrane modules.In addition,this method of anti-fouling filtration for microorganisms can be extended to the industrial production of various bioenergy sources and will have very promising practical applications.

Simple and Ultrahigh Efficient Superhydrophilic Polydopamine-coated TiO_(2) Cotton for Oil-water Separation

Oil–water mixing has brought many problems to a society, and it is of great significance to develop a simple, convenient, efficient, and durable separation material to solve the problem of oil–water mixing. In this paper, modified cottons were successfully prepared using polydopamine as the in situ mineralization site of TiO_(2) nanoparticles combined with synergistic crosslinking with KH550. A large number of hydrophilic groups endowed the cotton with superhydrophilic ability, which greatly shortened its water spreading time. The prepared modified cotton could be successfully separated from oil and water, and still had a separation efficiency of 99.999% after 50 cycles. In addition, after 24 h immersion in 1 M HCl, NaOH, and NaCl solutions and 50 abrasion experiments, the modified cotton showed excellent oil–water separation ability, and the separation efficiency was above 99.990%. Successfully provided a simple preparation method to prepare high-efficiency and clean cottons for oil–water separation.

Superhydrophilic Polydopamine‑Modified Carbon‑Fiber Membrane with Rapid Seawater‑Transferring Ability for Constructing Efficient Hanging‑Model Evaporator

Solar-driven seawater desalination has attracted much attention for alleviating global freshwater shortage,but the practical application is often limited by complicated fabrication processes,unsatisfactory seawater-transferring and severe salt accu-mulation on the photothermal membranes.To solve these problems,hydrophobic industrial-grade carbon fiber membrane(CFM)with good photoabsorption was surface-modified with polydopamine(PDA)to prepare superhydrophilic CFM@PDA for the construction of efficient hanging-model evaporators without salt accumulation.The coating of PDA on CFM is realized by simple self-polymerization of dopamine,and the as-prepared CFM@PDA exhibits high solar absorption effi-ciency of 96.7%,good photothermal effect and superhydrophilicity.Especially,when CFM@PDA is hanging between two water tanks(one contains seawater and the other is empty)in a flat hanging-model evaporator,it can transport seawater at a high rate(26.35 g/h)which is 3.6 times that(7.28 g/h)of commercial cotton fabric.Under simulated sunlight(1.0 kW m^(-2))irradiation,CFM@PDA shows a high evaporation rate of 1.79 kg m^(-2) h^(-1) with a solar evaporation efficiency of 92.6%.Even if NaCl solution with a high concentration(21.0 wt%)is used for the evaporation,the hanging CFM@PDA can retain a high evaporation rate(~1.80 kg m^(-2) h^(-1))without salt accumulation during the long-time test(8 h),which is significantly better than that of the tradition floating model.Therefore,this study not only demonstrates the simple preparation of super-hydrophilic CFM@PDA,but also promotes the further practical applications of hanging-model evaporators for continuous salt-free desalination.

Pool boiling on the superhydrophilic surface with TiO_2 nanotube arrays

Surface with TiO2 nanotube arrays(TNTAs)is superhydrophilic and of great specific area.This paper investigates the pool boiling characteristics at the thermal interface with TNTAs.The results show that the TNTAs interface can enhance the pool boiling heat transfer compared to the pure Ti metal plate.The bubbles formed at the initial nucleation state are very small and released in higher frequency.The pool boiling heat transfer enhancement at the TNTAs interface may be attributed to the high density of nucleate site,high intrinsic heating area of nanotubes layer,superhydrophilicity and the vertically oriented nanotube structure.

Hierarchical structures hydrogel evaporator and superhydrophilic water collect device for efficient solar steam evaporation

Efficient light absorption and trapping are of vital importance for the solar water evaporation by hydrogel-based photothermal conversion materials.Conventional strategies are focused on the development of the composition and structure of the hydrogers internal network.In our point of view,the importance of the surface structure of hydrogel has usually been underestimated or ignored.Here inspired by the excellent absorbance and water transportation ability of biological surface structure,the hierarchical structured hydrogel evaporators(HSEs)increased the light absorption,trapping,water transportation and water-air interface,which is the beneficial photothermal conversion and water evaporation.The HSEs showed a rapid evaporation rate of 1.77 kg·m^(-2)·h^(-1)at about 92%energy efficiency under one sun(1 kW·m^(-2)).Furthermore,the superhydrophilic window device was used in this work to collect the condensed water,which avoids the light-blocking caused by the water mist formed by the small droplets and the problem of the droplets stick on the device dropping back to the bulk water.Integrated with the excellent photothermal conversion hydrogel and superhydrophilic window equipment,this work provides efficient evaporation and desalination of hydrogel-based solar evaporators in practical large-scale applications.

Stretchable and Superhydrophilic Polyaniline/Halloysite Decorated Nanofiber Composite Evaporator for High Efficiency Seawater Desalination

Here,authors report on composition of a stretchable,mechanically durable and superhydrophilic polyaniline(PANI)/hal-loysite nanotubes(HNTs)decorated PU nanofiber(PANI/HNTs@PU).The polymer nanofibers are placed as the core and PANI/HNTs makes the shell section.The PANI/HNTs creates a membrane with outstanding light absorption and photo-thermal conversion performance.The strong solar absorption capability and superhydrophilicity of the PANI/HNTs@PU remain almost unchanged during stretching,abrasion,and ultrasonic washing tests,exhibiting superior surface stability and durability.When the PANI/HNTs@PU is used for the interfacial evaporation,the evaporation rate and efficiency reach as high as 1.61 kg m^(-2) h^(-1) and 94.7%,respectively.No salt precipitation is observed on the solar absorber surface even under a high salinity or during the long term or cyclic evaporation test.Furthermore,the excellent interfacial evaporation function is maintained when the nanofiber composite is mechanically stretched.The PANI/HNTs@PU based evaporation device shows promising applications in high performance solar desalination.

An unusual superhydrophilic/superoleophobic sponge for oil-water separation

Development of porous materials with anti-fouling and remote controllability is highly desired for oil-water separation application yet still challenging. Herein, to address this challenge, a sponge with unusual superhydrophilicity/superoleophobicity and magnetic property was fabricated through a dip-coating process. To exploit its superhydrophilic/superoleophobic property, the obtained sponge was used as a reusable water sorbent scaffold to collect water from bulk oils without absorbing any oil. Owing to its magnetic property, the sponge was manipulated remotely by a magnet without touching it directly during the whole water collection process, which could potentially lower the cost of the water collection process. Apart from acting as a water-absorbing material, the sponge can also be used as affiliation material to separate water from oil-water mixture and oil in water emulsion selectively, when fixed into a cone funnel. This research provides a key addition to the field of oil-water separation materials.

Fabrication of 3D biomimetic composite coating with broadband antireflection, superhydrophilicity, and double p-n heterojunctions

The traditional single material with two-dimensional （2D） biomimetic moth-eye structures is limited by its narrowband antireflection and single functional capability. To overcome these disadvantages, we exploited wet etching and hydrothermal synthesis coupled with chemical oxidation for fabricating a three- dimensional （3D） biomimetic moth-eye coating with ternary materials （polypyrrole nanoparticles, TiO2 nanorods, and Si micropyramids, i.e., PPy/TiOa/Si-p）. This coating reduced the reflectivity to 〈4% at wavelengths ranging from 200 to 2,300 nm and exhibited remarkable superhydrophilidty with a low water contact angle of 1.8°. Moreover, the composite coating had double p-n heterojunctions, allowing the high-efficiency separation of photogenerated carriers. The photo- current density of PPy/TiO2/Si-p was more than three times higher than that of TiO2/Si-p at a positive potential of 1.5 V. The proposed method provides a means to enhance solar energy conversion.

Fabrication of Transparent Superhydrophilic TiO_2 Nanofilm without UV-irradiation

A transparent phase-pure anatase TiO2 nanofilm was prepared through magnetron sputtering method,and a subsequent annealing treatment awarded it the superhydrophilic characteristic.To make clear the mechanism of the heat-induced superhydrophilicity,the chemical composition and surface morphology of the film were investigated in detail and compared before and after the annealing treatment mainly by field emission scanning electron microscopy(FESEM),X-ray diffraction method(XRD),Raman spectroscopy,and X-ray photoelectron spectroscope(XPS).The results suggest that the probable mechanism is in accordance with the UV-induced mechanism,where the heat-induced surface oxygen vacancies and hydroxyl radicals play important roles for achieving the superhydrophilicity.

Broadband Antireflective Superhydrophilic Thin Films with Outstanding Mechanical Stability on Glass Substrates

A facile approach was developed to fabricate visible/near-infrared antireflective(AR),superhydrophilic and anti-fogging thin films on glass substrates.Glass substrate was first etched by H_(2)SiF_(6)-based vapor and then dip-coated sequentially in a base-catalyzed 20 nm SiO_(2)nanoparticles sol and an acid-catalyzed SiO_(2)sol.After an-nealing,the prepared thin film(named E/BSiO_(2)/ASiO_(2))not only showed good optical and wetting properties,but also exhibited excellent mechanical properties.The thin film has enhanced transmittance in the spectral range of UV to near-infrared.The maximum transmittance of E/BSiO_(2)/ASiO_(2)thin film coated glass substrate is 98.4%in 400-1200 nm and 96.1%in 1200-2500 nm,respectively.Comparing with blank glass substrate,the average transmittance increases by 5%in the wavelength range of 300-2500 nm.Meanwhile,the film showed good anti-fogging performance.SEM and AFM were employed to characterize the morphology of the thin film.The pre-pared thin film has potential application in various areas,like solar cells,windowpanes and eyeglasses,and may also find applications in membrane-based separation,selective catalysis and sensors.

Flow-directed assembly of non-spherical titania nanoparticles into superhydrophilic thin films

Superhydrophilic thin films of 21 nm sized non-spherical titania nanoparticles are fabricated from a colloidal suspension by fixed blade flow coating without UV illumination. At a blade angle of a= 36° and a gap of d= 300 μm, hierarchically structured films with increasing surface roughness along with microscopic voids are formed depending on the substrate velocity and the titania volume fraction. Increasing the roughness is shown to be concomitant to an increase in the hydrophilicity, eventually leading to superhydrophilicity or water contact angle less than 5°.

Transparent and anti-fogging AlPO_(4)-5 films constructed by oblique oriented nano-flake crystals

In the present work,transparent and anti-fogging AlPO_(4)-5 films were prepared on glass substrates using a novel developed process.The process entails a simple in-situ sol–gel followed by vapor phase transport.The in-situ sol–gel process was implemented by coating the precursor sols for the synthesis of AlPO4-5 on the glass substrates successively using the spin-coating method.The films and powders scribed from the films were characterized by X-Ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscope(SEM),atomic force microscope(AFM),X-ray photoelectron spectroscopy and transmission electron microscope(TEM).The unique films were composed of oblique oriented nanoflake AlPO_(4)-5 crystals with the thickness of about 20 nm.The formation of nano-flake crystals can be ascribed to the high concentration of the precursors,resulting in the formation of a supersaturation system.The obtained films showed high antifogging performance due to the superhydrophilicity with a water contact angle of lower than 1.0°.The silicone oil contact angle was also low about 8.2°.In addition,heteroatom-substituted AlPO_(4)-5 films showing different colors can be obtained easily by simply adding transition metal ions in the phosphate acid solution during the preparation that can extend the application of the method for different coating demand.

Residual stress induced wetting variation on electric brush-plated Cu film

Nanocrystalline Cu film with a mirror surface finishing is prepared by the electric brush-plating technique. The as- prepared Cu film exhibits a superhydrophilic behavior with an apparent water contact angle smaller than 10°. A subsequent increase in the water contact angle and a final wetting transition from inherent hydrophilicity with water contact angle smaller than 90° to apparent hydrophobicity with water contact angle larger than 90° are observed when the Cu film is subjected to natural aging. Analysis based on the measurement of hardness with nanoindentation and the theory of the bond-order-length-strength correlation reveals that this wetting variation on the Cu film is attributed to the relaxation of residual stress generated during brush-plating deposition and a surface hydrophobization role associated with the broken bond polarization induced by surface nanostructure.