Recent Advancements in Polysulfone Based Membranes for Fuel Cell (PEMFCs, DMFCs and AMFCs) Applications: A Critical Review

In recent years, ion electrolyte membranes (IEMs) preparation and properties have attracted fabulous attention in fuel cell usages owing to its high ionic conductivity and chemical resistance. Currently, perfluorinatedsulfonicacid (PFSA) membrane has been widely employed in the membrane industry in polymer electrolyte membrane fuel cells (PEMFCs); however, NafionTM suffers reduced proton conductivity at a higher temperature, requiring noble metal catalyst (Pt, Ru, and Pt-Ru), and catalyst poisoning by CO. Non-fluorinated polymers are a promising substitute. Polysulfone (PSU) is an aromatic polymer with excellent characteristics that have attracted membrane scientists in recent years. The present review provides an up-to-date development of PSU based electrolyte membranes and its composites for PEMFCs, alkaline membrane fuel cells (AMFCs), and direct methanol fuel cells (DMFCs) application. Various fillers encapsulated in the PEM/AEM moiety are appraised according to their preliminary characteristics and their plausible outcome on PEMFC/DMFC/AMFC. The key issues associated with enhancing the ionic conductivity and chemical stability have been elucidated as well. Furthermore, this review addresses the current tasks, and forthcoming directions are briefly summarized of PEM/AEMs for PEMFCs, DMFCs, AMFCs.

Fe-MIL-101 modified by isatin-Schiff-base-Co: a heterogeneous catalyst for C–C, C–O, C–N, and C–P cross coupling reactions

Fe-MIL-101-isatin-Schiff-base-Co was synthesized and applied as a catalyst for Ullmann-type, Buchwald–Hartwig, Hirao, Hiyama and Mizoroki–Heck cross-coupling reactions of aryl halides.

Enhanced proton conductivity of Nafion-azolebisphosphonate membranes for PEM fuel cells

Azolebisphosphonates were prepared and used as dopants to obtain new Nafion doped membranes, which exhibited higher proton conductivities than that of Nafion.

A simple strategy based on a highly fluorinated polymer blended with a fluorinated polymer containing phosphonic acid to improve the properties of PEMFCs

Phosphonic acid containing fluorinated blend membranes led to new PEMFCs with a proton conductivity of 40 mS cm⁻¹ at 80 °C.

A mild electroassisted synthesis of (hetero)arylphosphonates

The first example of a nickel-catalyzed electrochemical coupling between dimethyl phosphite and (hetero)aryl halides to furnish (hetero)arylphosphonates is described.

Direct phosphonation of quinoxalin-2(1H)-ones under transition-metal-free conditions

A direct C–H bond phosphonation of quinoxalin-2(1H)-ones with H-phosphonates, H-phosphinates or H-phosphine oxides has been developed.

Synthesis of arylphosphonates catalyzed by Pd-imino-Py-γ-Fe2O3 as a new magnetically recyclable heterogeneous catalyst in pure water without requiring any additive

Arylphosphonates were synthesized in the presence of Pd-imino-Py-γ-Fe₂O₃ in pure water without using any additive.

Polymer brush functionalized SiO2 nanoparticle based Nafion nanocomposites: a novel avenue to low-humidity proton conducting membranes

Polymer brush grafted SiO₂ NPs provide Nafion nanocomposite membranes with superior proton conductivities at ambient and moderately high temperatures over the entire range of relative humidity.

Synthesis of highly phosphonic acid functionalized benzene-bridged periodic mesoporous organosilicas for use as efficient dye adsorbents

Periodic mesoporous organosilicas (PMOs) with benzene bridging groups in the silica wall were functionalized with a tunable content of phosphonic acid groups. These bifunctional materials were synthesized by co-condensation of two different organosilane precursors, that is, 1,4-bis(triethoxysilyl)benzene (BTEB) and sodium 3-(trihydroxysilyl)propyl methyl phosphate (SPMP), under acidic conditions using nonionic surfactant Brij-S10 as template. The materials exhibited well-ordered mesostructures and were characterized by X-ray diffraction, nitrogen sorption, TEM, TGA, FTIR, and solid-state NMR measurements. The materials thus obtained were employed as adsorbents to remove different types of dyes, for example, cationic dyes methylene blue and phenosafranine, anionic orange II, and amphoteric rhodamine B, from aqueous solutions. The materials exhibited a remarkably high adsorption capacity than activated carbon due to their ordered mesostructures, a large number of phosphonic acid groups, and high surface areas. The adsorption was mainly governed by electrostatic interaction, but also involved π-π stacking interaction as well as hydrogen bonding. The adsorption kinetics can be better fitted by the pseudo-second order model. The adsorption process was controlled by the mechanisms of external mass transfer and intraparticle diffusion. The materials retained more than 97% dye removal efficiency after use for five consecutive cycles.

Visualization of clusters in polymer electrolyte membranes by electron microscopy

The morphology of ionic clusters that form in polyelectrolyte membranes has a strong effect on transport and electrical properties. In spite of considerable research effort the link between morphology and properties has not been clearly established, mainly due to difficulties in assessing nanoscale morphology. Electron microscopy (EM) has the potential to visualize morphology. However success in visualization has so far been moderate. In this review we focus on the potential of EM techniques to characterize the ionic domains. We use both experimental data and models to compare the capabilities of several EM techniques: BF TEM, HAADF, core-loss EELS, and low-loss EELS in projection imaging and STEM modes. The main problems common for all these EM modes are radiation damage and overlap of features in projection. Our models show that core loss EELS with exposures that are below the typical damage threshold is incapable of resolving 2 nm diameter sulfur-rich clusters in PEMs. While low loss EELS requires lower exposure, the insight it can provide is quite limited. HAADF and BF TEM present the most effective modes for imaging the sulfur clusters in PEMs. While BF TEM uses scattered electrons more efficiently, HAADF using slightly higher doses can provide unique information due to in-focus imaging and transparent interpretation of the images. Fortunately, in at least some interesting cases the clusters themselves are much more radiation resistant than the polymer and can be studied at exposures high enough to obtain clear images. Our simulations also show that tomographic 3D reconstruction provides the best approach for solving the overlap problem. In spite of the abilities of electron tomography, data obtained from all EM techniques improve if thin sections are studied. We briefly discuss methods for obtaining such sections.