Enhancing the mechanical properties of zirconia/Nafion® nanocomposite membrane through carbon nanotubes for fuel cell application

Construction of High-Performance Membranes for Vanadium Redox Flow Batteries: Challenges, Development, and Perspectives

While being a promising candidate for large-scale energy storage, the current market penetration of vanadium redox flow batteries (VRFBs) is still limited by several challenges. As one of the key components in VRFBs, a membrane is employed to separate the catholyte and anolyte to prevent the vanadium ions from cross-mixing while allowing the proton conduction to maintain charge balance in the system during operation. To overcome the weakness of commercial membranes, various types of membranes, ranging from ion exchange membranes with diverse functional groups to non-ionic porous membranes, have been designed and reported to achieve higher ionic conductivity while maintaining low vanadium ion permeability, thus enhancing efficiency. In addition, besides overall efficiency, stability and cost-effectiveness of the membrane are also critical aspects that determine the practical applicability of the membranes and thus VRFBs. In this article, we have offered comprehensive insights into the mechanism of ion transportation in membranes of VRFBs that contribute to the challenges and issues of VRFB applications. We have further discussed optimal strategies for solving the trade-off between the membrane efficiency and its durability in VRFB applications. The development of state-of-the-art membranes through various material and structure engineering is demonstrated to reveal the relationship of properties-structure-performance.

A wearable enzyme sensor enabled by the floating-gate OECT with poly(benzimidazobenzophenanthroline) as the catalytic layer

With the advantages of miniaturization, simple device structure, and fast response, the organic electrochemical transistor (OECT) has become an emerging platform for developing wearable enzyme sensors for real-time health monitoring. The floating gate (FG) OECT employs a distinct signal acquisition and amplification structure, mitigating the effects of non-specific physical adsorption during the sensing process and preventing contamination of the electrolyte solution by side reaction products. The current work reports a feasible wearable enzyme sensor using a poly(benzimidazobenzophenanthroline) (BBL)-Nafion-enzyme-Nafion stacking structure as the sensing layer of the FG OECT. Based on the experimental results, the BBL film with an area of 3.14 mm2 and a thickness of 175 nm can generate an open circuit potential of 199.61 mV in 10- 1 M hydrogen peroxide compared with the blank control. Then, the FG OECT is integrated with the flexible microfluidic systems for on-skin detection of glucose, lactate, and uric acid with sensitivities of 92.47, 152.15, and 74.27 µA·dec- 1, respectively. This FG OECT-based wearable enzyme sensor will open new windows for multiplexed detection of sweat metabolites.

Antimicrobial coatings based on amine-terminated graphene oxide and Nafion with remarkable thermal resistance

We present a novel type of layer-by-layer (LbL) waterborne coating based on Nafion and amine-terminated graphene oxide (GO-NH2) that inhibits the growth of Escherichia coli and Staphylococcus aureus by more than 99% and this performance is not compromised upon extensive thermal annealing at 200 °C. Quartz crystal microbalance (QCM) sensorgrams allow the real time monitoring of the build-up of the LbL assemblies, a process that relies on the strong electrostatic interactions between Nafion (pH = 2.7, ζ = -54.8 mV) and GO-NH2 (pH = 2, ζ = 26.7 mV). Atomic force microscopy (AFM), contact angle and zeta potential measurements were used to characterise the multilayer assemblies. We demonstrate here that Nafion/GO-NH2 advanced coatings can offer drug-free and long-lasting solutions to microbial colonization and can withstand dry heat sterilization, without any decline in their performance.

Fabrication of pore-filling cation-exchange membrane from waste polystyrene and Spunbond Meltblown Spunbond (SMS) non-woven polypropylene fabric as the substrate

Commercial ion-exchange membranes are typically thick, possessing limited mechanical strength, and have relatively high fabrication costs. In this study, we utilize a three-layer polypropylene fabric known as Spunbond Meltblown Spunbond (SMS) as the substrate. This choice ensures that the resulting membrane exhibits high strength and low thickness. SMS substrates with various area densities, including 14.5, 15, 17, 20, 25, and 30 g/m2, were coated with different concentrations of waste polystyrene solution (ranging from 5 × 104 to 9 × 104 mg/l) before undergoing sulfonation using concentrated sulfuric acid. The physicochemical and mechanical properties of the membrane were characterized and compared with those of commercial Neosepta CMX and Nafion-117 cation-exchange membranes. Remarkably, the fabricated membrane exhibited good performance compared to commercial ones. The cation-exchange capacity (2.76 meq/g) and tensile strength (37.15 MPa) were higher, and the electrical resistance (3.603Ω) and the thickness (130 μm) were lower than the commercial membranes.

A Critical Review of Electrolytes for Advanced Low- and High-Temperature Polymer Electrolyte Membrane Fuel Cells

In the 21st century, proton exchange membrane fuel cells (PEMFCs) represent a promising source of power generation due to their high efficiency compared with coal combustion engines and eco-friendly design. Proton exchange membranes (PEMs), being the critical component of PEMFCs, determine their overall performance. Perfluorosulfonic acid (PFSA) based Nafion and nonfluorinated-based polybenzimidazole (PBI) membranes are commonly used for low- and high-temperature PEMFCs, respectively. However, these membranes have some drawbacks such as high cost, fuel crossover, and reduction in proton conductivity at high temperatures for commercialization. Here, we report the requirements of functional properties of PEMs for PEMFCs, the proton conduction mechanism, and the challenges which hinder their commercial adaptation. Recent research efforts have been focused on the modifications of PEMs by composite materials to overcome their drawbacks such as stability and proton conductivity. We discuss some current developments in membranes for PEMFCs with special emphasis on hybrid membranes based on Nafion, PBI, and other nonfluorinated proton conducting membranes prepared through the incorporation of different inorganic, organic, and hybrid fillers.

Characterisation and modelling the mechanics of cellulose nanofibril added polyethersulfone ultrafiltration membranes

The performance of the membranes can be improved by adding the appropriate amount of nanomaterials to the polymeric membranes that can be used for water/wastewater treatment. In this study, the effects of polyvinylpyrrolidone (PVP), the impact of different amounts (0.5% and 1% wt.) of cellulose nanofibril (CNF), and the combined effects of PVP-CNF on the properties/performance of the polyethersulfone-based (PES-based) membrane are investigated. All PES-based ultrafiltration (UF) membranes are manufactured employing the phase inversion method and characterised via Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and the relevant techniques to determine the properties, including porosity, mean pore size, contact angle, water content, and pure water flux tests. Furthermore, the thermal properties of the prepared membranes are investigated using thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) techniques. Experimental and numerical methods are applied for the mechanical characterisation of prepared membranes. For the experimental process, tensile tests under dry and wet conditions are conducted. The finite element (FE) method and Mori-Tanaka mean-field homogenisation are used as numerical methods to provide more detailed knowledge of membrane mechanics.

Prospects of Polymeric Nanocomposite Membranes for Water Purification and Scalability and their Health and Environmental Impacts: A Review

Water shortage is a major worldwide issue. Filtration using genuine polymeric membranes demonstrates excellent pollutant separation capabilities; however, polymeric membranes have restricted uses. Nanocomposite membranes, which are produced by integrating nanofillers into polymeric membrane matrices, may increase filtration. Carbon-based nanoparticles and metal/metal oxide nanoparticles have received the greatest attention. We evaluate the antifouling and permeability performance of nanocomposite membranes and their physical and chemical characteristics and compare nanocomposite membranes to bare membranes. Because of the antibacterial characteristics of nanoparticles and the decreased roughness of the membrane, nanocomposite membranes often have greater antifouling properties. They also have better permeability because of the increased porosity and narrower pore size distribution caused by nanofillers. The concentration of nanofillers affects membrane performance, and the appropriate concentration is determined by both the nanoparticles' characteristics and the membrane's composition. Higher nanofiller concentrations than the recommended value result in deficient performance owing to nanoparticle aggregation. Despite substantial studies into nanocomposite membrane manufacturing, most past efforts have been restricted to the laboratory scale, and the long-term membrane durability after nanofiller leakage has not been thoroughly examined.