High-performance Membrane Materials Research Articles

Recent Advances in High-Performance Membrane Materials for Fuel Cells

Fuel cells have emerged as a key technology for clean energy production, with proton exchange membrane (PEM) fuel cells being one of the most promising types due to their high efficiency and low emissions. A critical component of PEM fuel cells is the membrane, which plays a crucial role in ion transport and overall system performance. Recent advances in membrane materials have focused on improving proton conductivity, chemical stability, and durability while reducing production costs. This review discusses recent developments in high-performance membrane materials, including polymer blends, hybrid membranes, and metal-organic frameworks (MOFs). These innovative materials have shown significant potential in overcoming the limitations of traditional membranes like Nafion®. Advances in acid-base membranes, such as polybenzimidazole (PBI)-based systems, have demonstrated improvements in high-temperature performance. Enhanced cross-linking techniques, the use of antioxidant additives, and nanofillers have further contributed to improved membrane durability. Despite these advancements, challenges remain in scaling up production and reducing costs. Future research must focus on addressing these issues to enable the widespread commercial use of fuel cells. The progress in membrane material technology is critical to realizing the potential of fuel cells as a viable solution for sustainable energy.

Material Aspects of Thin-Film Composite Membranes for CO2/N2 Separation: Metal-Organic Frameworks vs. Graphene Oxides vs. Ionic Liquids.

Thin-film composite (TFC) membranes containing various fillers and additives present an effective alternative to conventional dense polymer membranes, which often suffer from low permeance (flux) and the permeability-selectivity tradeoff. Alongside the development and utilization of numerous new polymers over the past few decades, diverse additives such as metal-organic frameworks (MOFs), graphene oxides (GOs), and ionic liquids (ILs) have been integrated into the polymer matrix to enhance performance. However, achieving desirable interfacial compatibility between these additives and the host polymer matrix, particularly in TFC structures, remains a significant challenge. This review discusses recent advancements in TFC membranes for CO2/N2 separation, focusing on material structure, polymer-additive interaction, interface and separation properties. Specifically, we examine membranes operating under dry conditions to clearly assess the impact of additives on membrane properties and performance. Additionally, we provide a perspective on future research directions for designing high-performance membrane materials.

In situ polymerization of a poly(3,4-ethylenedioxythiophene):poly(sodium–styrennesulfonate) conductive layer for electro-assisted ultrafiltration and fouling mitigation

Electrification can enhance the antifouling performance of ultrafiltration membranes and improve the sustainability of membrane technologies. The design of high-performance conductive membrane materials remains one of the core technologies in electro-assisted ultrafiltration. Here, conductive PVDF/PEDOT:PSS composite membranes were prepared via in situ chemical oxidation polymerization on a PVDF surface. The PVDF/PEDOT:PSS membranes were subsequently used for electro-filtration to study the effect of the applied potential on humic acid fouling. When a voltage of 3 V was applied, the PVDF/PEDOT:PSS20 membrane was continuously polluted for 5 cycles. The results showed that after simple hydraulic cleaning, the membrane flux recovery rate reached 91 %. Compared with that of the PVDF membrane, the irreversible fouling of the PVDF/PEDOT:PSS20 membrane decreased by 65 %. The modified Poisson Boltzmann equation indicates that applying cathodic potential on the surface of PEDOT:PSS conductive layer increases the cumulative concentration of counter ions on the membrane surface and the thickness of the charged layer, thereby promoting the migration of peak forces on the membrane surface to the bulk solution, changing the fouling behaviour of HA from cake filtration to standard blocking.

Advanced Preparation Methods for Ceramic Membrane Materials in Electrochemical Applications

The outstanding thermal, chemical, and mechanical properties of ceramic membranes have attracted increasing attention, offering advantages over polymer and metal counterparts. Exploring the specialized applications of ceramic membranes through various preparation methods poses a daunting challenge for contemporary researchers. Traditional preparation methods are essentially unable to meet the requirements of complex membrane structures. For instance, in ceramic fuel cell applications, cells composed of ceramic membrane materials exhibit high resistance and low conductivity, which seriously hinders the progress of new high-performance ceramic fuel cells. Therefore, it is necessary to improve preparation methods to improve the electrochemical performance of devices composed of ceramic membrane materials. In recent years, breakthroughs in various new processing technologies have propelled the performance of ceramic membrane devices. This paper will focus on the following aspects. Firstly, traditional preparation methods and advanced preparation methods of ceramic membrane materials will be discussed. Secondly, high-performance ceramic membrane materials prepared by different advanced preparation methods are introduced, and the electrochemical properties of the devices composed of ceramic membrane materials are elaborated in combination with different testing and characterization methods. Finally, the prospects and future direction of the preparation of ceramic membrane materials by advanced preparation methods are summarized.

Research advances of cardo fluorene-based polymer based membranes for gas separation

Gas membrane separation has become one of the technologies to solve major problems in energy, environment and other fields. As the foundation and core of membrane separation technology, high performance membrane materials have always been the focus of research. Membranes based on organic polymer materials are the main commercial gas separation membranes due to their advantages of high design freedom, easy membrane formation and low cost. However, the application of most membranes based on polymer materials are limited by the mutual restriction between permeability and selectivity. The introduction of large volume and twisted groups into the polymer chain can effectively improve gas separation performance. Fluorenyl shows unique large space volume and rigid twisted structure, the introduction of which in polymers will limit the free rotation of the polymer backbone, forming loose accumulations of chain to increase the free volume, eventually improving the gas separation performance of the membranes. Therefore, fluorenyl is favored in the field of gas separation membranes. In this paper, the recent studies on membranes based on fluorene-based polymer materials in the field of gas separation are reviewed. These researches are classified by the structure of polymer materials that make up the membranes and introduced in terms of synthesis, separation mechanism and performance. Finally, the future research directions of fluorene-based polymer gas separation membrane is prospected.

Biosorption of halophilic fungal melanized membrane – PUR/melanin polymer for heavy metal detoxification with electrospinning technology

ABSTRACT Eradication of heavy metal pollution has become the prime priority over the conservation of water resources in the upcoming era. Herein, the study involved the halophilic fungal melanin from Curvularia lunata showed a promising biosorbent for the removal of toxic heavy metals which shows eco-friendly, cost-effective, high stability, and adsorbent efficiency. Polyurethane blended with fungal melanin polymers, makes polymeric nanofibrous membranes through electrospinning techniques. BET isotherms revealed the raw fungal melanin holds a surface area of 3.54 m2/g exhibiting type IV isotherms. BJH results in a total pore volume of 5.79 cc/g with a pore diameter of 6.54 ± 1 nm for pores smaller than 4544.8 Å. Exhibits Eumelanin properties were characterized by FE – SEM and FTIR functional elements. ICPMS confirmed the metal adsorption proficiency on both raw and melanized membranes before and after treatments. Over 17 heavy metals, Ni2+ were adsorbed with 100% efficiency by raw melanin alone with 42.48 µg/L of Ni2+ concentration in the water sample, whereas, Cu2+, Zn2+, Co2+, Cr2+, Pb2+, Mn2+, Al3+, Mo6+, Sb3+, Ba2+, Fe2+, and Mg2+ stands next with 99%. In this study, gentle/simple application of raw fungal melanin (without PUR tailored) can detoxify the maximum concentration of heavy metals present in the water bodies which are further used for irrigation and even drinking purposes. This mycoremediation approach can be easily adapted to industrial production than other high-performance membrane materials with minimal process modification, making it a promising strategy for improving the adsorption properties used in various applications after still furthermore investigation.

Poly(aryl ether sulfone ketone) with densely sulfonated structural units facilitate microphase separation to promote proton transport

The development of high-performance and low-cost membrane materials is crucial for proton exchange membrane fuel cells. To improve the proton conductivity, we designed a novel multiple phenyls monomer. Then, we synthesize a series of sulfonated poly(aryl ether sulfone ketone) membranes (SPAESK-x). The hydrophilic groups are densely distributed in units after sulfonation, which can form large hydrophilic ion clusters and provide more connected channels for proton transport. The large hydrophilic ion clusters facilitate the separation of hydrophilic and hydrophobic phases to form wider proton transport channels. The SPAESK-15 membrane achieves a high proton conductivity (181.0 mS cm-1) at 80 °C. The novel monomer and polymers are budget and simple to synthesize, offering the possibility of large-scale preparation. Overall, the novel structure has the potential to develop high-performance electrolyte materials.

Chiral metal-organic cage modified polyvinylidene fluoride membrane via metal phenolic networks for enantioseparation

High-performance chiral membrane materials hold great promise for the separation of pharmacological enantiomers. The key to achieving high-enantioselective chiral membrane separation is the development of suitable chiral membrane materials. However, traditional chiral separation membranes still face several limitations, including the main problem of the permeability-selectivity trade-off. In this study, a kind of novel chiral metal–organic cage (MOC) modified polyvinylidene fluoride (PVDF) membrane, namely PVDF@TA-Zn@MOC, was fabricated successfully by growing the chiral MOC [Zn3L2] onto the surface of PVDF substrate membranes induced by tannic acid (TA)-Zn2+ (TA-Zn) networks. In brief, ultrathin TA-Zn2+ metal-phenolic network coating was first adhered onto the surface of PVDF substrate membranes, followed with the in-situ growth of chiral MOC [Zn3L2] that was triggered by the coordination-enabled adhesion of Zn2+. A series of chiral PVDF@TA-Zn@MOC membranes were prepared with different hydrophilic properties and MOC loading by adjusting the concentrations of TA and metal/ligand. The transport and separation performances of these membranes were investigated for the mandelic acid (MA) enantiomers, and as a result, when the addition of TA was 1 mg and the metal ion concentration was 3.125 × 10-3 mol·L-1, the chiral membrane PVDF@TA-Zn@MOC-2 exhibited the most extraordinary entrapment ability in both permeability and selectivity for D-MA with an enantiomeric excess value of up to 71 % at a feed solution concentration of 300 ppm for 6 h under the neutral conditions. This method allows for the construction of the chiral hydrophilic MOC nanocoating membranes, which has the potential to broaden the applications of chiral MOC.

Preparation of strong, water retention, and multifunctional soybean flour-based adhesive inspired by lobster shells and milk skin

The development of a water-retaining soybean flour-based adhesive with high water resistance, interfacial adhesion and mildew resistance is significant in replacing petroleum-based aldehyde-based resin. Drawing inspiration from lobster shells, soybean flour (SF), self-synthesized epoxy hyperbranched hydroxyethyl cellulose (EH) and calcium phosphate (CaP) oligomers were employed to prepare organic-inorganic hybrid composite adhesives based on hyperbranched structure. The EH component, abundant in active groups, enhanced the interfacial adhesion of the adhesives and served as an organic carrier for the mineralization of CaP oligomers. Prior to adhesive solidification, CaP oligomers mineralized to form an inorganic film akin to milk skin, which prevented water evaporation, resulting in a water retention time of 100 min for the adhesive. During adhesive curing, CaP oligomers with fluid-like behavior polymerized and mineralized, ultimately forming a continuous inorganic network of CaP crystals. This network, combined with the organic substrates (SF and EH), constituted an organic-inorganic hybrid structure, which bolstered the water and mildew resistance (20 days) of the adhesives. The prepressing intensity and wet shear strength of the resultant plywood increased by 168% and 396% to 0.67 MPa and 1.39 MPa, respectively, compared to those of the unmodified adhesive. The strength reached the leading level of the reported soybean flour adhesives. The biomimetic strategy employed here can be extended to high-performance gels and membrane materials, offering a novel modification approach for bio-composites.

A novel antifouling polyamide thin-film composite forward osmosis membrane fabricated by poly(m-phenylene isophthalamide) for seawater desalination

Forward osmosis (FO) technology has attracted the interest of many researchers due to its excellent properties such as low energy consumption, fouling resistance, and easy cleaning. However, the lack of high-performance membrane materials makes it far from being practical on a large scale application. In this study, the poly(m-phenylene isophthalamide) (PMIA) was used as the substrate to be embedded in a high-porosity polyester mesh to form a support layer, and a forward osmosis composite membrane was prepared through an interfacial polymerization process. The effects of preparation conditions such as mesh size, scraping membrane thickness, and casting solution concentration on performance were studied. In the FO operation mode, with DI water as the feed solution and 1 mol/L NaCl as the draw solution, the water flux is 8.62 L•m−2•h−1, the reverse salt flux is 0.118 mol•m−2•h−1, and the rejection for NaCl exceeds 99%. Moreover, the membrane behaved excellent mechanical properties, with a tensile strength of 95 MPa. Compared with the two commercial FO membranes, the self-made PMIA TFC-FO showed excellent hydrophilicity and fouling resistance. This research demonstrated that PMIA is a proper candidate for fabricating of the TFC-FO membranes to achieve high water flux and selectivity in seawater desalination.

Impact of concentration polarization on membrane gas separation processes: From 1D modelling to detailed CFD simulations

Membranes are one key technology for gas separation. Current design methodologies make use of a 1D set of mass balance equations with membrane taken as the only mass transfer resistance (no concentration polarization hypothesis). This strategy has however to be reconsidered with emerging high-performance membrane materials. Accordingly, a rigorous CFD simulation approach is developed in order to correctly compute their separation efficiency. The results reveal that, compared to CFD, in the presence of concentration polarization, 1D models largely overestimate the separation performance of high-performing membranes. Based on a generic modelling of mass transfer in the gas phase under concentration polarization, a novel 1D modified approach is reported, showing similar predictions compared to CFD simulations, but offering very fast computations. This strategy is of interest for the simple and systematic design of membrane gas separation processes, including process synthesis approaches.

Effect of oxygen atoms and cyano groups on mixed gas separation of PIM-1 membranes: MD simulations

The polymer of intrinsic microporosity PIM-1 shows a unique structure prevented intra-chain and inter-chain aggregation and produces high porosity and the possibility of functionalization, it is considered as a promising candidate for applications in the field of gas separation. In this work, PIM-1 membranes were constructed with 21-step method via molecular dynamics (MD) simulations, the structure information of PIM-1 membrane and their separation performances on CO2/N2 mixture was explored. The influence of functional groups on adsorption and permeation behavior of CO2/N2 mixture was explored, the transport mechanism and separation mechanism were also illustrated. The simulation results revealed that the permeation behavior of CO2/N2 mixture through PIM-1 membrane is a solubility-dominated separation mechanism, and the cyano group in PIM-1 chain and terminal hydroxyl groups play an important role in the gas adsorption and permeation process. Overall, this study provides valuable insights for the design and preparation of high-performance membrane materials.

Nanostructured membranes with interconnected pores via a combination of phase inversion and solvent crystallisation approach

Polyethersulfone (PES) is an important membrane material in wastewater and medical applications due to its outstanding thermal and mechanical properties. However, when processing the PES into the asymmetric membranes through nonsolvent-induced phase separation (NIPS) method, the emergence of macro voids and discrete porosities has hampered its permeation performance. In this study, we present a novel phase inversion and solvent crystallisation approach that combines NIPS with the combined crystallisation and diffusion (CCD) technique, named as (NIPS-CCD) to significantly improve PES ultrafiltration membrane permeation without use of any additives. The NIPS-CCD method is simple and requires only a change in casting plate material and water bath temperature. The resultant membrane features a typical NIPS-like skin layer and elongated finger like structure, which are integrally connected to aligned microchannels formed through the CCD technique. With the enhanced pore connectivity, a 50-fold increase in water permeation up to 771 LMH bar−1 was obtained from the NIPS-CCD membrane with the pore size of 6–7 nm. This approach can be easily adapted to industrial production for other high-performance membrane materials with a minimal process modification, making it a promising strategy for improving the permeation properties of membranes used in various applications.

Structure and Performance of All-Green Electrospun PHB-Based Membrane Fibrous Biomaterials Modified with Hemin

This work addresses the challenges concerning the development of "all-green" high-performance biodegradable membrane materials based on poly-3-hydroxybutyrate (PHB) and a natural biocompatible functional additive, iron-containing porphyrin, Hemin (Hmi) via modification and surface functionalization. A new facile and versatile approach based on electrospinning (ES) is advanced when modification of the PHB membranes is performed by the addition of low concentrations of Hmi (from 1 to 5 wt.%). Structure and performance of the resultant {HB/Hmi membranes were studied by diverse physicochemical methods, including differential scanning calorimetry, X-ray analysis, scanning electron microscopy, etc. Modification of the PHB fibrous membranes with Hmi allows control over their quality, supramolecular structure, morphology, and surface wettability. As a result of this modification, air and liquid permeability of the modified electrospun materials markedly increases. The proposed approach provides preparation of high-performance all-green membranes with tailored structure and performance for diverse practical applications, including wound healing, comfort textiles, facial protective masks, tissue engineering, water and air purification, etc.

Preliminary exploration of the dye/salt separation performance of 2D and 3D covalent organic frameworks/nylon 6 membranes prepared by layer-by-layer strategy

Covalent organic frameworks (COFs) had been widely studied as high-performance separation membrane materials because of their uniform pore size, high porosity and good stability. In this work, 1,3,5-tris(4-aminophenyl)benzene (TAPB) - 1,3,5-triformylphloroglucinol (Tp)-12/nylon 6 membrane, a two-dimensional (2D) COFs membrane, and 4-[tris(4-aminophenyl)methyl]aniline (TAPM) -Tp-6/nylon 6 membrane, a three-dimensional (3D) COFs membrane, were prepared by layer-by-layer strategy. During the experiment, these COFs/nylon 6 membranes showed good properties, such as high water permeance (4522 L m−2 h−1 bar−1 for TAPB-Tp-12/nylon 6 membrane, and 4840 L m−2 h−1 bar−1 for TAPM-Tp-6/nylon 6 membrane), excellent dye rejection (methylene blue rejection>99.7 %), low salt rejection (<3.4 %), good chemical stability and reusability, which might be due to the hydrophilicity and electrical properties of these materials and the support of nylon 6 skeleton. Moreover, the possible reasons for these differences between 2D COFs membrane and 3D COFs membrane were analysed by summarizing and comparing the data obtained from these COFs/nylon 6 membranes. Therefore, this work not only provided a universal method for the synthesis of different types of COFs membranes, but also supplied a reference for researchers in the same field to compare the performance of 2D and 3D COFs membranes.

Core-dual-shell structure MnO2@Co–C@SiO2 nanofiber membrane for efficient indoor air cleaning

Developing cost-effective and high-efficient air purification materials for enhancing the indoor air quality has been an ongoing concern. Herein, MnO2/Co–C catalyst layers were wrapped on SiO2 nanofiber by a combination of thermal pyrolysis and redox reaction method to prepare catalytic membranes (MCCS-x) for the efficient purification of indoor PM and HCHO. The core-dual-shell structure maintains the pore structure of the membrane, providing high gas permeability of 670 m3·m−2·h−1·kPa−1. Owing to the introduction of MnO2/Co–C enhanced the capture of PM, the optimized MCCS-2 exhibits high filtration efficiency of PM0.3 and PM2.5 (99.60% and 99.99%) with a low pressure drop (<80 Pa). In addition, MCCS-2 achieves 100% HCHO removal efficiency at room temperature due to its large specific surface area, high redox property and abundant Mn4+ and oxygen species. The appropriate proportion of Mn/Co bimetallic sites synergy inhibits the formation of formate and carbonate intermediate species, thus MCCS-2 possesses excellent long-term catalytic stability than contrast sample (MCCS-3 and MS). This work demonstrates a new approach for the fabrication of high-performance catalytic membrane materials for indoor air purification.

Space and charge effect on the desalination performance of BNNT(8,8) membranes: A molecular dynamics study

Many factors have a noticeable impact on the performance of nanotubes. However, the dominant factors are still poorly understood. In this work, the molecular dynamics simulation was employed to study the charge effect of –NH3+ groups and their location on desalination performance. Our research shows that the desalination performance is influenced by the electrostatic interaction more than that caused by the steric hindrance. In addition, our research shows that the distribution of charge also affects desalination performance, which would give some guidance for further promoting the synthesis of high-performance membrane materials in the experiment.

Robust poly(alkyl–fluorene isatin) proton exchange membranes grafted with pendant sulfonate groups for proton exchange membrane fuel cells

The development of high-performance low-cost membrane materials is crucial for application in proton exchange membrane fuel cells (PEMFCs). In this study, two types of poly(alkyl–fluorene isatin)-based proton exchange membranes (PEMs) are designed and prepared successfully via facial superacid-catalyzed Friedel–Crafts polycondensation. The fluorene-based polymers exhibit good solubility and film-forming ability, and the produced PEMs possess excellent mechanical properties, dimensional stability, and oxidization stability because of the aromatic backbone. Atomic force microscopy showed that HFxDPy-PS-based PEMs have more significant phase separation structures than MFxDPy-PS-based PEMs due to the longer soft alkyl chains on the fluorene groups. HF3DP1-PS exhibits high proton conductivity that reached 88.56 mS cm−1 at 80 °C. The H2/O2 single fuel cell assembled with HF3DP1-PS exhibits a power density of 753 mW cm−2, which is close to that of a fuel cell with commercial Nafion 212 (774 mW cm−2) under the same conditions. All these results indicate the broad potential application of poly(alkyl–fluorene isatin)-based PEMs in PEMFCs.

Membrane Separation Processes and Post-Combustion Carbon Capture: State of the Art and Prospects.

Membrane processes have been investigated for carbon capture for more than four decades. Important efforts have been more recently achieved for the development of advanced materials and, to a lesser extent, on process engineering studies. A state-of-the-art analysis is proposed with a critical comparison to gas absorption technology, which is still considered as the best available technology for this application. The possibilities offered by high-performance membrane materials (zeolites, Carbon Molecular Sieves, Metal Oxide Frameworks, graphenes, facilitated transport membranes, etc.) are discussed in combination to process strategies (multistage design, hybrid processes, energy integration). The future challenges and open questions of membranes for carbon capture are finally proposed.

CO2/CH4 Separation via Carbon-Based Membrane: The Dynamic Role of Gas-Membrane Interface.

Membrane separation is considered one of the most promising CO2/CH4 separation technologies currently available because it is a safe, environment-friendly, and economical method. However, the inability of membrane materials to reconcile the trade-off between permeability and permeation selectivity limits their further applications; moreover, the mechanism underlying this process is unclear, which is mainly determined by the performance of gas adsorption and diffusion. Therefore, this paper describes the effect of gas adsorption and diffusion on membrane separation by assessing the fundamental gas-membrane and gas-gas interactions. Combining molecular simulation methods (Monte Carlo and molecular dynamics simulation) and a thermodynamic model called "linearized nonequilibrium thermodynamic transfer model", we investigate the permeability and permeation selectivity for CO2/CH4 in five carbon-based membranes and propose a general method for screening membrane materials. The interaction-dominated mechanism derived in this work provides new insights into membrane separation and facilitates the screening of high-performance membrane materials.