Design of pendent imidazolium side chain with flexible ether-containing spacer for alkaline anion exchange membrane

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.

Investigating the suitability of poly tetraarylphosphonium based anion exchange membranes for electrochemical applications

Anion exchange membranes (AEMs) are becoming increasingly common in electrochemical energy conversion and storage systems around the world (EES). Proton-/cation-exchange membranes (which conduct positive charged ions such as H⁺ or Na⁺) have historically been used in many devices such as fuel cells, electrolysers, and redox flow batteries. High capital costs and the use of noble metal catalysts are two of the current major disadvantages of polymer electrolyte membrane (PEM)-based systems. AEMs may be able to overcome the limitations of conventional PEMs. As a result, polymers with anion exchange properties have recently attracted a lot of attention due to their significant benefits in terms of transitioning from a highly acidic to an alkaline environment, high kinetics for oxygen reduction and fuel oxidation in an alkaline environment, and lower cost due to the use of non-precious metals. The aim of this research was to learn more about the development of a new AEM based on poly tetraarylphosphonium ionomers (pTAP), which has high ionic conductivity, alkaline stability, thermal stability, and good mechanical properties, making it a more cost-effective and stable alternative to conventional and commercial AEMs. A simple solution casting method was used to build novel anion exchange composite membranes with controlled thicknesses using the synthesized pTAP with polysulfone (PS). To ensure their suitability for use as an electrolyte in alkaline electrochemical systems, the composite membranes were characterized using FTIR, XRD, water uptake, ionic conductivity, and alkaline stability. At 40 °C, the PS/pTAP 40/60 percent membrane had a maximum ionic conductivity of 4.2 mS/cm. The thermal and mechanical stability of the composite membranes were also examined, with no substantial weight loss observed up to 150 °C. These findings pave the way for these membranes to be used in a wide variety of electrochemical applications.

Electron-Donating C-NH2 Link Backbone for Highly Alkaline and Mechanical Stable Anion Exchange Membranes

Aryl-ether cleavage and benzylic quaternary ammonium (QA) group degradation are promoted by C═O groups in most commercial anion exchange membrane materials. Herein, a novel strategy of converting C═O groups to the electron-donating C-NH₂ linkages in conventional poly(arylene ether ketone)s is proposed by reductive amination via Leuckart reaction. Density functional theory (DFT) calculations indicate that the model compound containing C-NH₂ linkage exhibits much higher barrier heights for aryl-ether cleavage and QA group degradation by enhancing the electronic cloud density on both the ether-connected carbon and the benzylic carbon. The C-NH₂ linkages also induce hydrogen bond networks in the membranes, which enhance intermolecular interaction and provide additional hydroxide transport sites. As a result, the C-NH₂ linkage membranes exhibit excellent hydroxide conductivity (108.2 mS cm^-1 at 80 °C) and tensile strength (48.4 MPa) with high elongation at break (50.8%). The C-NH₂ linkage membranes also show outstanding alkaline stability with no detectable backbone degradation even in 4 M KOH at 80 °C for 400 h, which is at the top-level among the state-of-the-art main chain architecture AEMs. This study proposes a new strategy for the synthesis of highly stable AEMs based on electron-donating C-NH₂ link backbone.

Synthesis of Imidazolium based PILs and Investigation of Their Blend Membranes for Gas Separation

Polymeric (ionic liquid) (PIL) copolymers bearing cationic imidazolium pendants and polar acrylic acid groups (P(VBCImY-co-AA_x)), which both favor the interaction with CO₂ molecules, have been synthesized and blended with film forming, high glass transition temperature aromatic polyether-based pyridinium PILs (PILPyr). The blend membranes based on the above combination have been prepared and characterized in respect to their thermal and morphological behavior as well as to their gas separation properties. The used copolymers and blends showed a wide range of glass transition temperatures from 32 to 286 °C, while blends exhibited two phase morphology despite the presence of polar groups in the blend components that could participate in specific interactions. Finally, the membranes were studied in terms of their gas separation behavior. It revealed that blend composition, counter anion type and acrylic acid molar percentage affect the gas separation properties. In particular, PILPyr-TFSI/P(VBCImTFSI-co-AA₂₀) blend with 80/20 composition shows CO₂ permeability of 7.00 Barrer and quite high selectivity of 103 for the CO₂/CH₄ gas pair. Even higher CO₂/CH_4. selectivity of 154 was achieved for PILPyr-BF₄/P(VBCImBF₄-co-AA₁₀) blend with composition 70/30.

A Design of Experiment Approach for Ionic Liquid-Based Extraction of Toxic Components-Minimized Essential Oil from Myristica fragrans Houtt. Fruits †

The effect of the addition of ionic liquids (ILs) during the hydrodistillation of Myristica fragrans Houtt. (nutmeg) essential oil was studied. The essential oil of M. fragrans is characterized by the presence of terpenes, terpenoids, and of phenylpropanoids, such as methyl eugenol and safrole, that are regarded as genotoxic and carcinogenic. The aim of the work was to determine the best ionic liquid to improve the yield of the extraction of M. fragrans essential oil and decrease the extraction of toxic phenylpropanoids. Six ILs, namely 1,3-dimethylimidazolium chloride (1), 1,3-dimethylimidazolium dimethylphosphate (2), 1-(2-hydroxyethyl)-3-methylimidazolium chloride (3), 1-(2-hydroxyethyl)-3-methylimidazolium dimethylphosphate (4), 1-butyl-3-methylimidazolium chloride (5), and 1-butyl-3-methylimidazolium dimethylphosphate (6), were prepared by previously reported, innovative methods and then tested. An experimental design was used to optimize the extraction yield and to decrease the phenylpropanoids percentage using the synthesized ILs. The influence of the molarity of ILs was also studied. MODDE 12 software established 0.5 M 1-butyl-3-methylimidazolium chloride as the best co-solvent for the hydrodistillation of M. fragrans essential oil.

Thermodynamics of Counterion Release Is Critical for Anion Exchange Membrane Conductivity

As the field of anion exchange membranes (AEMs) employs an increasing variety of cations, a critical understanding of cation properties must be obtained, especially as they relate to membrane ion conductivity. Here, to elucidate such properties, metal cation-based AEMs, featuring bis(norbornene) nickel, ruthenium, or cobalt complexes, were synthesized and characterized. In addition, isothermal titration calorimetry (ITC) was used to probe counterion exchange thermodynamics in order to understand previously reported differences in conductivity. The ion conductivity data reported here further demonstrated that nickel-complex cations had higher conductivity as compared to their ruthenium and cobalt counterparts. Surprisingly, bulk hydration number, ion concentration, ion exchange capacity, and activation energy were not sufficient to explain differences in conductivity, so the thermodynamics of metal cation-counterion association were explored using ITC. Specifically, for the nickel cation as compared to the other two metal-based cations, a larger thermodynamic driving force for chloride counterion release was observed, shown through a smaller Δ H_tot for counterion exchange, which indicated weaker cation-counterion association. The use of ITC to study cation-counterion association was further exemplified by characterizing more traditional AEM cations, such as quaternary ammoniums and an imidazolium cation, which demonstrated small variances in their enthalpic response, but an overall Δ H_tot similar to that of the nickel-based cation. The cation hydration, rather than its hydration shell or the bulk hydration of the membrane, likely played the key role in determining the strength of the initial cation-counterion pair. This report identifies for the first time how ITC can be used to experimentally determine thermodynamic quantities that are key parameters for understanding and predicting conductivity in AEMs.