Electrically Pore‐Size‐Tunable Polypyrrole Membrane for Antifouling and Selective Separation

Antifouling and selectivity are major challenges for membrane separation technology. Herein, a polypyrrole‐dodecylbenzene sulfonate (PPy‐DBS) membrane with tunable pores is fabricated to alleviate pore blocking and achieve selective separation. The insertion/extraction of ions during the electrical redox process causes the change of PPy‐DBS volume, so that the membrane pores can be tuned in situ by applying an external redox potential. The pore size of a fouled membrane is enlarged under an oxidation voltage, then the membrane is backwashed to eliminate foulants in the pores, after which membrane pore size is recovered under a reduction voltage. Thus, membrane fouling can be effectively alleviated by adjusting the membrane pore size combined with cleaning. The specific flux of PPy‐DBS membrane increased by 21.91% after applying the voltages and backwashing, and it exhibits great recycling performance. Moreover, the distribution of humic acid macromolecules in the permeate significantly decreased, proving the enhanced sieving effect of smaller membrane pores under negative voltage. This study provides an intelligent strategy for fouling prevention and selective separation in water treatment.     

Sub-2-nm Channels within Covalent Triazine Framework Enable Fast Proton-Selective Transport in Flow Battery Membrane

Ion conductive membranes (ICMs) with robust sub-2-nm channels show high proton transport rate in flow battery, but it remains a great challenge to precisely control the ion sieving of the membranes. Herein, as a promising proton-selective carrier, sulfonated piperazine covalent triazine framework (s-pCTF) with the channel size of ≈1.5 nm and abundant fast proton hopping sites is introduced into sulfonated poly(ether ether ketone) (SPEEK) to fabricate advanced ICM for vanadium flow battery (VFB) application. The interior protoplasmic channels of s-pCTF demonstrate significant Donnan exclusion effect, resulting in a high proton/vanadium ion selectivity in theory (6.22 × 10⁵). Meanwhile, the nitrogen-rich sub-2-nm channels yield fast proton highway, and exterior-grafted sulfonic acid groups further facilitate the proton transfer. By regulating the ion sieving and proton conductivity, the optimal hybrid membrane exhibits synchronously improved battery performance with an enhanced energy efficiency (92.41% to 78.53% at 40–200 mA cm⁻²) and long-term stability for 900 cycles over 400 h (EE: 87.2–85% at 120 mA cm⁻²), outperforming pure SPEEK and Nafion212 membranes. This study validates the applicability of organic porous CTF with sub-2-nm channels and desired functionality in ICMs for high-performance VFB application.     

Zr-MOF-Enabled Controllable Ion Sieving and Proton Conductivity in Flow Battery Membrane

Membrane with ordered channels is the key to controlling ion sieving and proton conductivity in flow batteries. However, it remains a great challenge for finely controlling the nanochannels of polymeric membranes. Herein, two types of acid-stable Zr-metal organic framework (MOF-801 and MOF-808) with variable pore structures and channel properties are introduced as fillers into a non-fluorinated sulfonated poly (ether ether ketone) (SPEEK). The membrane incorporated with MOF-801 of a smaller triangular window (≈3.5 Å) successfully translates the molecular sieving property into the flow battery membrane, resulting in enhanced coulombic efficiency (98.5–99.2%) at 40–120 mA cm⁻² compared with the pristine SPEEK membrane (97.1–98.5%). In contrast, more protophilic internal interconnected channels of MOF-808 yield faster proton highway, leading to a significant increase of voltage efficiency (93.7–84.1%) at 40–120 mA cm⁻² compared with the pristine SPEEK membrane (91.7–78.9%). By regulating the ion sieving and proton conductivity, MOF-801/MOF-808 binary composite membrane exhibits synchronously improved performance in the vanadium redox flow battery system. The revealed structure–property relationship in the Zr-MOFs-based membranes provides a general guideline to design new proton exchange membranes with ordered channels for flow battery application.     

Bioinspired Dynamic Antifouling of Oil-Water Separation Membrane by Bubble-Mediated Shape Morphing

Oil–water separation membranes easily fail to oil foulants with low surface energy and high viscosity, which severely limits these membranes’ applications in treating oily wastewater. Herein, an oil–water separation membrane by bioinspired bubble-mediated antifouling strategy is fabricated via growing hierarchical cobalt phosphide arrays on stainless steel mesh. The as-prepared membrane is superhydrophilic/superaerophobic and electrocatalytic for hydrogen evolution under water, which helps to rapidly generate and release abundant microbubbles surrounding the oil-fouled region on the membrane. These microbubbles can spontaneously coalesce with the oil foulants to increase their buoyancy and warp their interface tension by morphing the oil shape. And this spontaneous coalescence also increases the kinetic energy of oil foulants resulting from the decreased bubbles’ interface energy and potential energy. The synergy of the warped interface tension, increased buoyancy, and kinetic energy drives the efficiently dynamic antifouling of this membrane. This dynamic antifouling even can remove some solid sediment such as oily sand particles that causes more serious fouling of the membrane. Thus, this membrane maintains high flux (>11920 L m⁻² h⁻¹ bar⁻¹) in the long-term separation of oil–water and oil–sand–water emulsions by dynamically recovering the decayed flux on demand, which exhibits great potential in treating industrial oily wastewater.     

Advanced Charged Sponge‐Like Membrane with Ultrahigh Stability and Selectivity for Vanadium Flow Batteries

Advanced charged sponge‐like porous membranes with ultrahigh stability and selectivity are designed and fabricated for vanadium flow battery (VFB) applications. The designed porous membranes are fabricated via constructing positively charged cross‐linked networks on the pore walls of polysulfone membranes. The charge density of the pore walls can be tuned by changing the crosslinking time. The positively charged pore walls can effectively retain vanadium ions via Donnan exclusion, hence keeping extremely high selectivity, while the crosslinked network effectively increases the membrane stability. As a result, the designed membranes exhibit an outstanding performance, combining extremely high selectivity and stability. The single cell assembled with the prepared porous membrane shows a columbic efficiency of 99% and an energy efficiency of 86% at a current density of 80 mA cm^?2, which is much higher than Nafion 115 (93.5%; 82.3%). A battery assembled with the prepared membrane shows a stable battery performance over more than 6000 cycles, which is by far the longest record for porous membranes ever reported. These results indicate that advanced, charged, sponge‐like, porous membranes with a crosslinked pore‐wall structure are highly promising for VFB applications.     

3D Neighborhood Nanostructure Reinforces Biosensing Membrane

The electron signals in the cell can be rapidly and accurately transmitted by the spatially confined and adjacently distributed enzyme pairs anchored in the cytomembrane. As inspiration, by leverage of tannic acid-3-aminopropyltriethoxysilane-Fe (TA-APTES-Fe) ternary coating, for the first time, a mesoporous biosensing membrane is developed by orderly assembly and targeted confinement of Prussian blue (PB) and glucose oxidase (GOx) with neighborhood nanostructure in the 3D mesoporous carbon nanotubes (CNTs) membrane electrode. The mesoporous biosensing membrane extends the triple-phase boundary from conventional 2D contact to 3D contact, promotes the transfer rates of the cascade reactants, enhances the proximity of PB, GOx, and the electrode, and achieves in–situ removal of interferents, thereby elevating the utilization of PB, enhancing the cascade reaction efficiency, increasing the availability of the electroactive hydrogen peroxide (H₂O₂), and improving its stability. It exhibits superior sensitivity (31.2 µA mM⁻¹) and long-term stability in continuous glucose monitoring with a negligible response drift for up to 8 h. In addition, the multienzyme mimic functions of PB are employed to imitate the “loosening-degradation” membrane cleaning process via bubble scrubbing and Fenton oxidation, thereby fully regenerating the fouled biosensing membrane. This work provides a novel design strategy for biosensors toward efficient, reliable, and stable sensing.     

Ultraselective and Highly Permeable Polyamide Nanofilms for Ionic and Molecular Nanofiltration

Membranes with ultrahigh ion selectivity and high liquid permeance are needed to produce high-quality product water with increased recovery and process efficiency in water desalination. The narrow pore size distribution and controlled surface charge in the separation layer of nanofiltration membranes significantly improve the ion selectivity through molecular sieving and Donnan exclusion of co-ions. Here, the ultraselective and yet highly water permeable polyamide nanofilm composite nanofiltration membranes developed by precisely controlling the kinetics of the interfacial polymerization reaction by maintaining the stoichiometric equilibrium at the interface is reported. The kinetically favorable stoichiometric equilibrium condition prohibits the formation of aggregate pores in the nanofilm and leads to the formation of narrow network pores with a high surface negative charge. Nanofilms are designed with a controlled degree of crosslinking and made as thin as ≈7 nm to achieve increased water permeance. The ultraselective membranes exhibit up to 99.99% rejection of divalent salt (Na₂SO₄) and demonstrate monovalent to divalent ion selectivity of >4000. The selectivity of these nanofilm composite membranes is beyond the permeance–selectivity upper-bound line of the state-of-the-art nanofiltration membranes and one to two orders of magnitude higher than the commercially available membranes with pure water permeances of up to 23 L m⁻² h⁻¹ bar⁻¹. The fabrication process is scalable for membrane manufacturing.     

A Porous Skeleton-Supported Organic/Inorganic Composite Membrane for High-Efficiency Alkaline Water Electrolysis

Hydrogen energy is a truly renewable and clean energy source. Alkaline water electrolysis (AWE) is the most promising technology for green hydrogen production currently. In the AWE process, the critical part of an alkaline electrolyzer is the membrane, which acts to conduct hydroxide ions and block gases. However, developing low area resistance, high bubble point pressure and highly stable membrane for high-performance AWE is still a challenge. Herein, porous skeleton-supported composite membranes via the blade-coating method for advanced AWE are prepared. The porous composite membranes, besides having hydrophilic surface, also show ultra-low area resistance (≈0.15 Ω cm²), ultra-high bubble point pressure (≈27 bar) and excellent mechanical properties (tensile stress, ≈14 MPa). By using commercial catalysts, the composite membranes exhibit a current density of up to 1.9 A cm⁻² at the voltage of 2 V in 30 wt% KOH solution at 80 °C and achieve ultra-high H₂ purity (up to 99.996%) when applied in AWE. Notably, the composite membrane can operate for more than 1600 h without performance attenuation, demonstrating excellent stability. This study opens up the feasibility of preparing high-performance AWE membranes for large-scale hydrogen production.     

Silica Films with Bimodal Pore Structure Prepared by Using Membranes as Templates and Amphiphiles as Porogens

Extended porous silica films with thicknesses in the range of 60 to 130 μm and pores on both the meso‐ and macroscale have been prepared by simultaneously using porous membrane templates and amphiphilic supramolecular aggregates as porogens. The macropore size is determined by the cellulose acetate or polyamide membrane structure and the mesopores by the chosen ethylene‐oxide‐based molecular self‐assembly (block copolymer or non‐ionic surfactants). Both the template and the porogen are removed during an annealing step leaving the amorphous silica material with a porous structure that results from sol–gel chemistry occurring in the aqueous domains of the amphiphilic liquid‐crystalline phases and casting of the initial template membrane. The surface area and total pore volume of the inorganic films vary from 473 to 856 m² g^–1, and 0.50 to 0.73 cm³ g^–1, respectively, depending on the choice of template and porogen. The combined benefits of both macro‐ and mesopores can potentially be obtained in one film. Such materials are envisaged to have applications in areas of large molecule (biomolecule) separation and catalysis. Enhanced gas and liquid flow rates through such membranes, due to the presence of the larger pores, also makes them attractive as supports for other catalytic materials.     

Electrospinning Synthesis of Self-Standing Cobalt/Nanocarbon Hybrid Membrane for Long-Life Rechargeable Zinc–Air Batteries

Integrating high-efficiency oxygen electrocatalyst directly into air electrodes is vital for zinc–air batteries to achieve higher electrochemical performance. Herein, a self-standing membrane composed of hierarchical cobalt/nanocarbon nanofibers is fabricated by the electrospinning technique. This hybrid membrane can be directly employed as the bifunctional air electrode in zinc–air batteries and can achieve a high peak power density of 304 mW cm⁻² with a long service life of 1500 h at 5 mA cm⁻². Its assembled solid-state zinc–air battery also delivers a promising power density of 176 mW cm⁻² with decent flexibility. The impressive rechargeable battery performance would be attributed to the self-standing membrane architecture integrated by oxygen electrocatalysts with abundant cobalt–nitrogen–carbon active species in the hierarchical electrode. This study may provide effective electrospinning solutions in integrating efficient electrocatalyst and electrode for energy storage and conversion technologies.     

Functionally Modified Macroporous Membrane Prepared by using Pulsed Laser Deposition

Pulsed laser deposition (PLD) is used to deposit pure metals (Pt and Au) and a mixture of metals (Pt–Ru) at the surface of a porous aluminum anodic oxide (AAO) substrate. In the case of Pt, thick films (> 300 nm) with pore diameters larger than 150 nm (macroporous), replicating the pore structure of the underlying AAO substrate, are obtained when PLD is performed at high (> 50 eV at^–1) kinetic energy (E_k) conditions. At lower E_k conditions, the characteristic structure of the AAO membrane is not discernable in the deposited film. In that case, the substrate is entirely covered by a film, the structure of which is not different from that of a Pt film deposited on a flat Si substrate under the same conditions. AAO membranes modified by macroporous Au and Pt–Ru alloy films are also prepared, demonstrating that the concept can be applied to a wide range of materials. The mechanisms responsible for the replication of the substrate pore structure in the metallic layer are discussed. These functionally modified macroporous membranes are electroactive and this aspect has been emphasized by studying the electrocatalytic properties of Pt and Pt–Ru modified macroporous membranes for CO oxidation.     

A Bioinspired Capillary Force-Induced Driving Strategy for Constructing Ultra-Low-Pressure Separation Membranes

The development of low-pressure or pressureless self-driven membranes is important for saving energy and overcoming the critical trade-off effect in membrane separation processes. However, conventional self-driven membranes rely on gravity, which is effective in the separation of large-sized materials but is still ineffective in the fine separation of small molecules. Herein, inspired by the capillary effect that exists in nature, a capillary force-induced membrane-driving strategy for fine separation at ultra-low pressures is demonstrated. Hydrophilic nanoparticles are prepared by a cross-linking reaction between tannic acid and 3-aminopropyltriethoxysilane and then introduce them into membrane pores to simulate sand accumulation with an aim to generate the capillary force. The membrane is then used in ultra-low pressure membrane separation. Interestingly, it is found that the membrane has excellent performance in the separation of dye/salt mixtures (dye rejection > 99%, salt rejection < 10%) and a high permeate flux (160 L m⁻² h⁻¹) under near “zero pressure” conditions. Moreover, the structural stability of the membrane is verified. Introducing capillary forces into membranes as an autonomous driving force can be a promising universal approach that can be added up to the toolbox for the efficient preparation of separation membranes.     

Biomimetic Hygroscopic Fibrous Membrane with Hierarchically Porous Structure for Rapid Atmospheric Water Harvesting

Sorption-based atmospheric water generation (SAWG) is a promising strategy to alleviate the drinkable water scarcity of arid regions. However, the high-water production efficiency remains challenging due to the sluggish sorption/desorption kinetics. Herein, a composite sorbent@biomimetic fibrous membrane (PPy-COF@Trilayer-LiCl) is reported by mimicking nature's Murray networks, which exhibits outstanding water uptake performance of 0.77–2.56 g g⁻¹ at a wide range of relative humidity of 30%–80% within 50 min and fast water release capacity of over 95% adsorbed water that can be released within 10 min under one sun irradiation. The superior sorption–desorption kinetics of PPy-COF@Trilayer-LiCl are enabled by the novel hierarchically porous structure, which is also the critical factor to lead a directional rapid water transport and vapor diffusion. Moreover, as a proof-of-concept demonstration, a wearable SAWG device is established, which can operate 10 sorption–desorption cycles per day in the outdoor condition and produce a high yield of clean water reaching up to 3.91 kg m⁻² day⁻¹. This study demonstrates a novel strategy for developing advanced solar-driven SAWG materials with efficient water sorption–desorption properties.     

Ultra-Stable,Highly Proton Conductive,and Self-Healing Proton Exchange Membranes Based On Molecule Intercalation Technique and Noncovalent Assembly Nanostructure

Proton exchange membranes (PEMs) that can heal mechanical damage to restore original functions are imperative for fabricating reliable and durable proton exchange membrane fuel cells (PEMFCs). Here, an ultra-stable, highly proton conductive self-healing PEM via hydrogen-bonding complexation between Nafion and poly(vinyl alcohol) (PVA) followed by incorporation of sodium lignosulfonate (SLS) intercalation-modified graphene oxide (GO) and post-modification with 4-formylbenzoic acid (FBA) is presented. Notably, the introduction of GO complexes and post-modification of FBA molecules effectively improves the stability of composite membranes and also participate in the establishment of proton-conducting nanochannels. Compared with recast Nafion, the FBA-Nafion/PVA@SLS/GO composite membranes exhibit enhanced mechanical properties (36.2 MPa at 104.8% strain) and higher proton conductivity (0.219 S cm⁻¹ at 80 °C-100% RH and 23.861 mS cm⁻¹ at 80 °C-33% RH, respectively). More importantly, the incorporated PVA gives the FBA-Nafion/PVA@SLS/GO composite membranes superior self-healing capabilities that can heal mechanical damage of several tens of micrometers in size and restore their original proton conductivity under the operating conditions of the PEMFCs. This study opens an avenue toward the development of reliable and durable PEM for PEMFCs.     

Ultra‐Thin Self‐Assembled Protein‐Polymer Membranes: A New Pore Forming Strategy

Self‐assembled membranes offer a promising alternative for conventional membrane fabrication, especially in the field of ultrafiltration. Here, a new pore‐making strategy is introduced involving stimuli responsive protein‐polymer conjugates self‐assembled across a large surface area using drying‐mediated interfacial self‐assembly. The membrane is flexible and assembled on porous supports. The protein used is the cage protein ferritin and resides within the polymer matrix. Upon denaturation of ferritin, a pore is formed which intrinsically is determined by the size of the protein and how it resides in the matrix. Due to the self‐assembly at interfaces, the membrane constitutes of only one layer resulting in a membrane thickness of 7 nm on average in the dry state. The membrane is stable up to at least 50 mbar transmembrane pressure, operating at a flux of about 21 000–25 000 L m^?2 h^?1 bar^?1 and displayed a preferred size selectivity of particles below 20 nm. This approach diversifies membrane technology generating a platform for “smart” self‐assembled membranes.     

阳极氧化铝膜孔径的测量

论述了一种对阳极氧化铝膜孔径进行测定和评估的方法。此方法通过对已得的阳极氧化铝薄膜提取样本制备扫描电镜(SEM)图像进行处理和分析,最终得到膜孔的尺寸结果。阳极氧化铝膜的膜孔尺寸处在nm级别,对其测量误差的要求很高。而限于SEM的设备特性和精度,通过SEM读取的原始阳极氧化铝膜的图像存在着大量噪声(以椒盐噪声为主)。鉴于此,首先对阳极氧化铝膜的原始SEM图像进行多重滤波处理(中值滤波、各向异性扩散滤波以及阈值滤波),得到具有膜孔结构信息的阈值图像。经过多重滤波的这一阈值图像仍存在着很多污点,这些污点对阳极氧化铝膜膜孔尺寸的评估无任何意义,于是继续将阈值图像进行去污处理,最后通过设计的"染色"算法,实现了对膜孔尺寸的实际测量。实验证明,此方法的适用性较强。     

Hydrothermally Robust Molecular Sieve Silica for Wet Gas Separation

A major challenge in silica membranes for gas separation is to maintain a robust pore structure in the presence of steam. In this work, use of a carbonized template is proposed to reduce damage to the pore structure by inhibiting silica migration along the membrane pore surface. This departs from the conventional wisdom of creating hydrophobic surfaces to achieve hydrostability. The carbonized‐template molecular sieve silica (CTMSS) membranes can then be applied to clean‐energy systems such as hydrogen separation and carbon dioxide sequestration, and membrane reactors where steam is present.     

N-CNTs-Based Composite Membrane Engineered By A Partially Embedded Strategy: A Facile Route To High-Performing Zinc-Based Flow Batteries

Zinc-based flow batteries are promising for distributed energy storage due to their low-cost and high-energy density advantages. One of the most critical issues for their practical application is the reliability that results from the heterogeneous zinc deposition and dead zinc from falling off the electrode. Herein, nitrogen-doped carbon nanotubes (N-CNTs)-based composite membrane through a facilely partially embedded method is reported to enable a dendrite-free alkaline zinc-based flow battery. The results indicate that the electrically conductive N-CNTs functional layer can enhance the transport dynamics of charge carriers and homogenize electric field distribution in membrane–electrode interface, which induces the initial nucleation of metallic zinc from the carbon felt electrode to N-CNTs functional layer and further achieve a uniform and dense plating of metallic zinc in alkaline media. Thus, the engineered membrane enables a stable alkaline zinc–iron flow battery performance for more than 350 h at a current density of 80 mA cm⁻². Moreover, an energy efficiency of over 80% can be afforded at a current density of 200 mA cm⁻². The scientific finding of this study provides a new strategy on composite membranes design and their capability to adjust the plating of metallic zinc in alkaline media.     

Nanoporous biocapsules for the encapsulation of insulinoma cells:biotransport and biocompatibility considerations

This study investigates whether nanoporous micromachined biocapsules, with uniform membrane pore sizes of 24.5-nm, can be used to encapsulate insulin-secreting cells in vitro. This approach to cell encapsulation is based on microfabrication technology whereby immunoisolation membranes are bulk and surface micromachined to present uniform and well-controlled pore sizes as small as 10 nm, tailored surface chemistries, and precise microarchitectures. This study evaluates the behavior of insulinoma cells with micromachined membranes, the effect of matrix configurations within the biocapsule on cell behavior, as well as insulin and glucose transport through the biocapsule membranes.     

Zwitterionic Gradient Double-Network Hydrogel Membranes with Superior Biofouling Resistance for Sustainable Osmotic Energy Harvesting

Developing ion-selective membranes with anti-biofouling property and biocompatibility is highly crucial in harvesting osmotic energy in natural environments and for future biomimetic applications. However, the exploration of membranes with these properties in osmotic energy conversion remain largely unaddressed. Herein, a tough zwitterionic gradient double-network hydrogel membrane (ZGDHM) with excellent biofouling resistance and cytocompatibility for sustainable osmotic energy harvesting is demonstrated. The ZGDHM, composed of negatively charged 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as the first scaffold network and zwitterionic sulfobetaine acrylamide (SBAA) as the second network, is prepared by a two-step photopolymerization, thus creating continuous gradient double-network nanoarchitecture and then remarkably enhanced mechanical properties. As verified by the experiments and simulations, the gradient nanoarchitecture endows the hydrogel membrane with apparent ionic diode effect and space-charge-governed transport property, thus facilitating directional ion transport. Consequently, the ZGDHM can achieve a power density of 5.44 W m⁻² by mixing artificial seawater and river water, surpassing the commercial benchmark. Most importantly, the output power can be promoted to an unprecedented value of 49.6 W m⁻² at the mixing of salt-lake water and river water, nearly doubling up most of the existing nanofluidic membranes. This study paves a new avenue toward developing ultrahigh-performance osmotic energy harvesters for biomimetic applications.