Synthesis and characterization of Nafion/cross-linked PVP semi-interpenetrating polymer network membrane for direct methanol fuel cell

Advancements of Polyvinylpyrrolidone-Based Polymer Electrolyte Membranes for Electrochemical Energy Conversion and Storage Devices

Polymer electrolyte membranes (PEMs) play vital roles in electrochemical energy conversion and storage devices, such as polymer electrolyte membrane fuel cell (PEMFC), redox flow battery, and water electrolysis. As the crucial component of these devices, PEMs need to possess high ion conductivity and electronic insulation, remarkable mechanical and chemical stability, and outstanding isolation function for the materials on both sides of the cathode and anode. Polyvinylpyrrolidone has received widespread attention in the research of PEMs owing to its tertiary amine basic groups and exceptional hydrophilic properties. This review focuses on the application status of polyvinylpyrrolidone-based PEMs in PEMFC, vanadium redox flow battery, and alkaline water electrolysis, and describes in detail the key scientific problems in these fields, providing constructive suggestions and guidance for the application of polyvinylpyrrolidone-based PEMs in electrochemical energy conversion and storage devices.

Synthesis and Characterization of Novel Green Hybrid Nanocomposites for Application as Proton Exchange Membranes in Direct Borohydride Fuel Cells

Organic–inorganic nanocomposite membranes for potential application in direct borohydride fuel cells (DBFCs) are formulated from sulfonated poly(vinyl alcohol) (SPVA) with the incorporation of (PO4-TiO2) and (SO4-TiO2) nanotubes as doping agents. The functionalization of PVA to SPVA was done by using a 4-sulfophthalic acid as an ionic crosslinker and sulfonating agent. Morphological and structural characterization by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) confirmed the successful synthesis of the doping agents and their incorporation into the polymer. The influence of PO4-TiO2 and SO4-TiO2 doping and their content on the physicochemical properties of the nanocomposite membranes was evaluated. Swelling degree and water uptake gradually reduced to 7% and 13%, respectively, with increasing doping agent concentration. Ion exchange capacity and ionic conductivity of the membrane with 3 wt.% doping agents were raised 5 and 7 times, respectively, compared to the undoped one. The thermal and oxidative stability and tensile strength also increased with the doping content. Furthermore, lower borohydride permeability (0.32 × 10−6 cm2 s−1) was measured for the membranes with higher amount of inorganic doping agents when compared to the undoped membrane (0.71 × 10−5 cm2 s−1) and Nafion®117 (0.40 × 10−6 cm2 s−1). These results pave the way for a green, simple and low-cost approach for the development of composite membranes for practical DBFCs.

Novel chitosan-Nafion composite for fabrication of highly sensitive impedimetric and colorimetric As(III) aptasensor

In the present work, for the first time we takes the advantages of chitosan-Nafion (Chit-Naf) composite as a highly conductive surface platform and a novel CNT-based signal amplification strategy to develop a lable-free impedimetricaptamer-based sensor for highly sensitive detection of As(III). The electrochemical impedance spectroscopy (EIS) investigations surprisingly revealed that the glassy carbon electrode (GC) electrode modified with Chit-Naf composite had higher electron transfer kinetics compared the bare GC, GC/Naf and GC/Chit electrodes, which promises a great potential as an efficient platform in construction of biosensing assays. In this work, we employed a signal amplification strategy based on carbon nanotube-bovine serum albumin (CNT-BSA) hybrid system, by which sensitivity and detection limit of the aptasensor for the detection of As(III) were obtained to be 100.82 Ω nM^-1 and a of 74 pM, respectively. This protocol provided one of the lowest limits of detection for As(III) on aptamer-based electrodes recently described in the literature. Moreover, the change of the optical absorptive properties of CNTs upon biorecognition interactions provides a way to detect the biorecognition process and thus allowed us to design an optical As(III) aptasensor using the UV-Vis spectroscopic method. The discrimination capability of the fabricated aptasensor for recognizing As(III) in the presence of other metal ions and a complex matrix of waste water samples was successfully investigated. This protocol provided a new method for sensitive detection of As(III) with considerable advantages in terms of reproducibility, selectivity, being mediator free and regenerability of the sensing interface.

Performance and antifouling enhancement of polyethersulfone hollow fiber membranes incorporated with highly hydrophilic hydroxyapatite nanoparticles

Membrane fouling is one of the main drawbacks in water purification applications. The present work indicated that the fabricated HAp/PES hollow fiber membranes presented better hydrophilicity, permeation and anti-fouling performance compared to PES membranes.

A semi-interpenetrating network approach for dimensionally stabilizing highly-charged anion exchange membranes for alkaline fuel cells

There is a delicate balance between ion exchange capacity (IEC), conductivity, and dimensional stability in anion exchange membranes as higher charge content can lead to increased water uptake, causing excessive swelling and charge dilution. Using highly-charged benzyltrimethylammonium polysulfone (IEC=2.99 mEq g(-1) ) as a benchmark (which ruptured in water even at room temperature), we report the ability to dramatically decrease water uptake using a semi-interpenetrating network wherein we reinforced the linear polyelectrolyte with a crosslinked poly(styrene-co-divinylbenzene) network. These membranes show enhanced dimensional stability as a result of lower water uptake (75 % vs. 301 % at 25 °C) while maintaining excellent hydroxide conductivity (up to 50 mS cm(-1) at 25 °C). These improvements produced an enhanced alkaline fuel cell capable of generating 236 mW cm(-2) peak power density at 80 °C. This method is easily adaptable and can be a viable strategy for stabilizing existing systems.

The effects of hydroxyapatite nano whiskers and its synergism with polyvinylpyrrolidone on poly(vinylidene fluoride) hollow fiber ultrafiltration membranes

By introducing hydroxyapatite (HAP) nano whiskers as well as polyvinylpyrrolidone (PVP), poly(vinylidene fluoride) (PVDF)/PVP/HAP hollow fiber membranes were fabricated with the wet spinning method.

Nanofiber mats electrospun from composite proton exchange membranes prepared from poly(aryl ether sulfone)s with pendant sulfonated aliphatic side chains

The electrospun nanofiber mats revealed high porosity and an interconnected open pore structure. The nanofibers are clearly visible and uniform throughout the composite membrane, which was completely pore-filled.