Cyclodextrin modified, multication cross-linked high performance anion exchange membranes for fuel cell application

High-performance cation electrokinetic concentrator based on a γ-CD/QCS/PVA composite and microchip for evaluating the activity of P-glycoprotein without any interference from serum albumin

The development of cation electrokinetic concentrators (CECs) has been hindered by the lack of commercial anion-exchange membranes (AEMs). This paper introduces a γ-cyclodextrin-modified quaternized chitosan/polyvinyl alcohol (γ-CD/QCS/PVA) composite as an AEM, which is combined with a microchip to fabricate a CEC. Remarkably, the CEC only concentrates cationic species, thereby overcoming the interference of the highly abundant, negatively charged serum albumin in the blood sample. P-Glycoprotein (P-gp) is recognized as an efflux transporter protein that influences the pharmacokinetics (PK) of various compounds. The CEC was used to evaluate the activity of P-gp by detecting the positively charged rhodamine 123 (Rho123 is a classical substrate of P-gp) with no interference from serum albumin in the serum sample. Using the CEC, the enrichment factor (EF) of Rho123 exceeded 105-fold under DC voltage application. The minimal sample consumption of the CEC (<10 μL) enables reduction of animal sacrifice in animal experiments. Here, the CEC has been applied to evaluate the transport activity of P-gp in in vitro and in vivo experiments by detecting Rho123 in the presence of P-gp inhibitors or agonists. The results are in good agreement with those reported in previous reports. Therefore, the CEC presents a promising application potential, owing to its simple fabrication process, high sensitivity, minimal sample consumption, lack of interference from serum albumin and low cost.

Perspective: Morphology and ion transport in ion-containing polymers from multiscale modeling and simulations

Ion-containing polymers are soft materials composed of polymeric chains and mobile ions. Over the past several decades they have been the focus of considerable research and development for their use as the electrolyte in energy conversion and storage devices. Recent and significant results obtained from multiscale simulations and modeling for proton exchange membranes (PEMs), anion exchange membranes (AEMs), and polymerized ionic liquids (polyILs) are reviewed. The interplay of morphology and ion transport is emphasized. We discuss the influences of polymer architecture, tethered ionic groups, rigidity of the backbone, solvents, and additives on both morphology and ion transport in terms of specific interactions. Novel design strategies are highlighted including precisely controlling molecular conformations to design highly ordered morphologies; tuning the solvation structure of hydronium or hydroxide ions in hydrated ion exchange membranes; turning negative ion-ion correlations to positive correlations to improve ionic conductivity in polyILs; and balancing the strength of noncovalent interactions. The design of single-ion conductors, well-defined supramolecular architectures with enhanced one-dimensional ion transport, and the understanding of the hierarchy of the specific interactions continue as challenges but promising goals for future research.

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.

Efficient and Ultrafast Adsorption of Rhenium by Functionalized Hierarchically Mesoporous Silica: A Combined Strategy of Topological Construction and Chemical Modification

Radioactive Tc-99 released by nuclear accidents threatens the environment and human health due to its long half-life and strong transportability. A combined strategy synergizing topological construction and chemical modification was proposed for the synthesis of high-performance adsorbents for Re as an analogue to Tc. On the one hand, hierarchically mesoporous SiO₂ with a fibrous structure (F-SiO₂), a peculiar topology integrating wrinkled open mesopores around 12 nm and on-wall mesopores around 3 nm, was adopted as the substrate of adsorbents. The larger mesopores can act as the superhighway for mass transfer, while the abundant smaller mesopores provide numerous adsorption sites. On the other hand, a series of dicationic pyridine (DCP) derivative groups (-Py⁺C_nH_2nN⁺Me₃) were designed to functionalize F-SiO₂ for improving the adsorption performance toward ReO₄^- anions, the dominating form of Re in aqueous solution. Density functional theory (DFT) calculation combined with batch adsorption experiments revealed that the ReO₄^- adsorption on -Py⁺C₅H₁₀N⁺Me₃ was the most favorable when the length of the spacer between the two positively charged N atoms ranged from 2 to 7 carbons (n = 2-7). However, -Py⁺C₅H₁₀N⁺Me₃ exhibited a much slower adsorption rate than -Py⁺C₂H₄N⁺Me₃. The stronger interaction between ReO₄^- and -Py⁺C₅H₁₀N⁺Me₃ suppresses the adsorbate diffusion. The two positive charges of -Py⁺C₅H₁₀N⁺Me₃ may be perpendicularly distributed, sterically hindering ReO₄^- transport in smaller mesopores. The longer and flexible carbon chains may be aggregated to form the hydrophobic region, repulsing the hydrated ReO₄^- anions. Therefore, the efficient and ultrafast Re adsorption was achieved by synergizing the unique topology of F-SiO₂ and functionalization by -Py⁺C₂H₄N⁺Me₃ with a shorter spacer and weaker affinity ReO₄^-. The detailed investigation demonstrated that -Py⁺C₂H₄N⁺Me₃ possessed exothermic adsorption nature, adequate radiation-resistance, and excellent reusability. Meanwhile, -Py⁺C₅H₁₀N⁺Me₃ exhibited stronger salinity tolerance and higher selectivity. The DCP groups are promising in decontamination of radioactive Tc, as they can meet specific requirements by manipulating the length of spacers.

Oriented Proton-Conductive Nanochannels Boosting a Highly Conductive Proton-Exchange Membrane for a Vanadium Redox Flow Battery

In this work, we propose a sulfonated poly (ether ether ketone) (SPEEK) composite proton-conductive membrane based on a 3-(1-hydro-imidazolium-3-yl)-propane-1-sulfonate (Him-pS) additive to break through the trade-off between conductivity and selectivity of a vanadium redox flow battery (VRFB). Specifically, Him-pS enables an oriented distribution of the SPEEK matrix to construct highly conductive proton nanochannels throughout the membrane arising from the noncovalent interaction. Moreover, the "acid-base pair" effect from an imidazolium group and a sulfonic group further facilitates the proton transport through the nanochannels. Meanwhile, the structure of the acid-base pair is further confirmed based on density functional theory calculations. Material and electrochemical characterizations indicate that the nanochannels with a size of 16.5 nm are vertically distributed across the membrane, which not only accelerate proton conductivity (31.54 mS cm^-1) but also enhance the vanadium-ion selectivity (39.9 × 10³ S min cm^-3). Benefiting from such oriented proton-conductive nanochannels in the membrane, the cell delivers an excellent Coulombic efficiency (CE, ≈ 98.8%) and energy efficiency (EE, ≈ 78.5%) at 300 mA cm^-2. More significantly, the cell maintains a stable energy efficiency over 600 charge-discharge cycles with only a 5.18% decay. Accordingly, this work provides a promising fabrication strategy for a high-performance membrane of VRFB.

Enhanced Hydroxide Conductivity and Dimensional Stability with Blended Membranes Containing Hyperbranched PAES/Linear PPO as Anion Exchange Membranes

A series of novel blended anion exchange membranes (AEMs) were prepared with hyperbranched brominated poly(arylene ether sulfone) (Br-HB-PAES) and linear chloromethylated poly(phenylene oxide) (CM-PPO). The as-prepared blended membranes were fabricated with different weight ratios of Br-HB-PAES to CM-PPO, and the quaternization reaction for introducing the ionic functional group was performed by triethylamine. The Q-PAES/PPO-XY (quaternized-PAES/PPO-XY) blended membranes promoted the ion channel formation as the strong hydrogen bonds interconnecting the two polymers were maintained, and showed an improved hydroxide conductivity with excellent thermal behavior. In particular, the Q-PAES/PPO-55 membrane showed a very high hydroxide ion conductivity (90.9 mS cm⁻¹) compared to the pristine Q-HB-PAES membrane (32.8 mS cm⁻¹), a result supported by the morphology of the membrane as determined by the AFM analysis. In addition, the rigid hyperbranched structure showed a suppressed swelling ratio of 17.9–24.9% despite an excessive water uptake of 33.2–50.3% at 90 °C, and demonstrated a remarkable alkaline stability under 2.0 M KOH conditions over 1000 h.