Search

To achieve a better performance of anion exchange membranes (AEMs), AEMs of a unique structure with flexible and dense side chains are prepared by taking amino groups on poly (aryl ether ketone)s (PAEKs) as reaction sites and grafting four long side chains on each repeat unit of main chains. This chemical synthetic route for the unique structure is simple and controllable, with no obvious side reactions happening during synthetic process. Three different kinds of cycloaminium cations are used as functional groups. The AEMs with this unique structure exhibit limited swelling ratios and improved hydroxide conductivities, of which the highest attains 74.4 mS cm−1 at 80 °C when using N-Methylmorpholine (Mm) as the cation group. The high conductivities are due to the formation of connective ion conducting channels facilitated by this kind of structure inside the membranes. No obvious changes in chemical structures of AEMs with different cations happen after alkali treatment for 768 h at 60 °C, indicating a good alkaline stability of AEMs with such specific structure. Moreover, the PAEK-MmOH yields a maximum power density of 302 mW cm−2 at 640 mA cm−2 when operating in a single fuel cell. Overall, these long-branched and densely functionalized AEMs with cycloaminium cation groups possess good application prospects in fuel cells. • Long-branched and densely functionalized anion exchange membranes are prepared. • The synthesis route for the unique structure is simple and controllable. • The membrane shows excellent performances. [ABSTRACT FROM AUTHOR]

A novel anion exchange membrane with tri-quaternized side chain has been developed in the present work. Di-cationic quaternary ammonium salt, 1-(4′-{1″-azonia-4″-azabicyclo [2.2.2] octyl} butyl) azonia-4-azabicyclo [2.2.2] octane (AABAA), is synthesized and used as tri-quaternization reagent. The tri-quaternized side chains enhance ionic interactions, which induce good micro-phase separation and excellent swelling resistance. Better aggregation of ionic clusters is observed in transmission electron microscopy (TEM) image in the tri-quaternized poly (ether sulfone) membrane (tri-QPESOH) compared to that in the mono-quaternized membrane (mono-QPESOH). Tri‐QPESOH membranes achieve a well-balanced performance between high hydroxide conductivity and dimensional stability. Especially, the tri-QPESOH membrane with IEC 2.31 mmol g −1 exhibits high hydroxide conductivity of 45.9 mS cm −1 at 25 °C and 130.9 mS cm −1 at 80 °C, and low swelling ratio of 21.5% even at 80 °C. Tri-QPESOH membranes also show improved thermal, mechanical and chemical stabilities. These observations suggest that the tri-cationic side chains provide a promising solution to the electrochemical-mechanical balance of anion exchange membranes. [ABSTRACT FROM AUTHOR]

ABSTRACT A mixed methanesulfonic acid/sulfuric acid solvent based chlromethylation of poly(ether ether ketone) (PEEK) is described. Methanesulfonic acid is the solvent, sulfuric acid is the catalyst, and chloromethyl octyl ether (CMOE) is the chloromethylating reagent. 1H-NMR spectra confirmed the successful synthesis of chloromethylated PEEK (CMPEEK). The effects of polymer concentration, catalyst/polymer ratio, and reaction temperature on the rate of PEEK chloromethylation were investigated. In order to minimize crosslinking, the PEEK concentration must be kept very low (< 2%). The reaction rate increases with increased catalyst/polymer ratio and reaction temperature. The activation energy of PEEK chloromethylation is 30.9 kJ mol−1. The extent of reaction for the new route is more easily controllable as compared with the previous sulfuric acid based route. The reaction rate constant at 25°C for the new route is 1.29 h−1 which is lower than that for chloromethylation by concentrated sulfuric acid at −10°C (rate constant 1.88 h−1). As a result, the degree of chloromethylation of CMPEEK can be easily controlled at room temperature using this mixed solvent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41404. [ABSTRACT FROM AUTHOR]

A series of soluble quaternized polyetherimides (QAPEIs) have been successfully synthesized by homogeneous quaternization in trimethylamine aqueous solution. 1H NMR spectra confirm the successful synthesis of QAPEI. The QAPEIs exhibit good solubility in membrane-preparation solvents, making it possible to prepare the QAPEI composite membrane. Novel composite hydroxide exchange membranes have been prepared by incorporating QAPEIs with polytetrafluoroethylene (PTFE) membranes. The SEM images, gas permeation measurements and FTIR spectra show that the QAPEI is successfully filled in PTFE membrane and the resulted composite membrane is dense and smooth. The ion exchange capacity of composite membranes ranges from 0.35 to 0.58 mmol g−1. The composite membranes have appropriate water uptake (≤154%) and moderate swelling ratio (≤42%) even at 60 °C. The hydroxide conductivity of the composite membrane reaches 11.9 mS cm−1 at 20 °C that increases to 35.2 mS cm−1 at 60 °C. TGA curve shows that the composite membrane possesses high thermal stability (T OD: 210 °C). All these properties indicate that the QAPEI/PTFE composite membranes are good candidates for use as HEMs in HEM fuel cells. [ABSTRACT FROM AUTHOR]

Abstract: A series of imidazolium-functionalized polysulfones were successfully synthesized by chloromethylation-Menshutkin two-step method. PSf-ImOHs show the desired selective solubility: insoluble in alcohols (e.g., methanol and ethanol), and soluble in 50 vol.% aqueous solutions of acetone or tetrahydrofuran, implying their potential applications for both the alcohol-resistant membranes themselves and the ionomer solutions in low-boiling-point water-soluble solvents. PSf-ImOH also possesses very high thermal stability (T OD: 258 °C), higher than quaternary ammonium and quaternary phosphonium functionalized polysulfones (T OD: 120 °C and 186 °C, repsectively). Ion exchange capacity (IEC) of PSf-ImOH membranes ranges from 0.78 to 2.19 mmol g−1 with degree of chloromethylation from 42% to 132% of original chloromethylated polysulfone. As expected, water uptake, swelling ratio, and hydroxide conductivity increase with IEC and temperatures. With 2.19 mmol g−1 of IEC, the PSf-ImOH 132% membrane exhibits the highest hydroxide conductivity (53 mS cm−1 at 20 °C), higher than those of all other reported polysulfone-based HEMs (1.6–45 mS cm−1) and other imidazolium-functionalized HEMs (19.6–38.8 mS cm−1). In addition, PSf-ImOH membranes have low methanol permeability of 0.8–4.7 × 10−7 cm2 s−1, one order of magnitude smaller than that of Nafion212 membrane. All these properties indicate imidazolium-functionalized polysulfone is very promising for potential applications in alkaline membrane direct alcohol fuel cells. [Copyright &y& Elsevier]

Abstract: Chloromethylated PEEK (CMPEEK) was successfully synthesized for the first time by concentrated sulfuric acid as the solvent and its degree of chloromethylation (DC) was controlled (38–98%) by varying the chloromethylation time. The sulfonation of PEEK was confirmed to be negligible during the chloromethylation by 1H NMR analysis. CMPEEKs are soluble in high-boiling-point solvents, which makes it possible to prepare CMPEEK membranes. Subsequently, it was quaternized and ion-exchanged by NaOH to form quaternized PEEK hydroxide (QAPEEKOH) membrane. The ion exchange capacity of QAPEEKOH membranes ranges from 0.43 to 1.35mmolg−1, and the corresponding degree of quaternization of chloromethyl group increases from 35% to 61%. QAPEEKOH membranes from DC of 38–70% have appropriate water uptake (≤145%) and moderate swelling ratio (≤27%) even at 60°C. More importantly, their hydroxide conductivities, such as 12mScm−1 at 30°C and 0.95mmolg−1 of IEC, are higher than those of most other quaternized aromatic polymer membranes. TGA shows that QAPEEKOH has high thermal stability (T OD: 148°C). All the above properties indicate that QAPEEKOH membrane is very promising for the potential application in hydroxide exchange membrane fuel cells. [Copyright &y& Elsevier]

Sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) is a kind of novel non‐fluorine polymer, whose high proton conductivity is dependent on high degree of sulfonation, which resulting in loss of dimensional stability. SPPESK/superacid sulfated zirconia (SZrO2) composite proton exchange membranes are fabricated first. The composite membrane shows good dimensional stability, ascribing to the restriction effect of hydrogen bonding force on the mobility and relaxation of polymer chains. Introducing SZrO2 simultaneously enhances the conductivity and anti‐methanol permeation, owing to the connected ion domains, enlarged and aggregated ion clusters, excess proton conduction sites, and good blocking effect to methanol of SZrO2. For composite membrane containing 1.5 wt % SZrO2, the highest conductivity of 180 mS cm−1 is obtained at 80 °C. Compared with pristine SPPESK and Nafion 115, the methanol permeability is reduced by 54 and 77%, and the maximum power density of direct methanol fuel cell is enhanced by 133 and 25%. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46758. [ABSTRACT FROM AUTHOR]

High-performance anion exchange membranes (AEMs) are in need for practical application of AEM fuel cells. Novel branched poly(ether ether ketone) (BPEEK) based AEMs were prepared by the copolymerization of phloroglucinol, methylhydroquinone and 4,4′-difluorobenzophenone and following functionalization. The effects of the branched polymer structures and functional groups on the membrane's properties were investigated. The swelling ratios of all the membranes were kept below 15% at room temperature and had good dimensional stability at elevated temperatures. The branching degree has almost no effect on the dimensional change, but plays a great role in tuning the nanophase separation structure. The cyclic ammonium functionalized membrane showed a lower conductivity but a much better stability than imidazolium one. The BPEEK-3-Pip-53 membrane with the branching degree of 3% and piperidine functionalization degree of 53% showed the best performances. The ionic conductivity was 43 mS cm−1 at 60 °C. The ionic conductivity in 1 M KOH at 60 °C after 336 h was 75% of its initial value (25% loss of conductivity), and the IEC was 83% of its initial value (17% loss of IEC), suggesting good alkaline stability. The peak energy density (60 °C) of the single H 2 /O 2 fuel cell with BPEEK-3-Pip-53 membrane reached 133 mW cm−2 at 260 mA cm−2. • A novel branched poly(ether ether ketone) based AEM was prepared. • The branched AEMs showed high conductivity and low swelling ratio. • A high peak power density was achieved for single cell with the branched AEM. [ABSTRACT FROM AUTHOR]

A high performance of anion exchange membranes (AEMs) is highly demanded in anion exchange membrane fuel cells (AEMFCs) and has been extensively studied. However, the poor ionic conductivities and the alkaline stability might limit their applications. Herein, we developed a novel strategy to improve the ionic conductivity and alkaline stability of AEMs by introducing hydrophilic oligo(ethylene glycol)(OEG) groups. Continuous ion-conducting channels were efficiently formed thanks to the dynamic aggregation of water molecules assisted by the hydrophilic side chains. The resultant AEMs with low IEC values showed significant enhancement in hydroxide conductivity compared to the AEMs functionalized by the conventional 1,2-dimethylimidazolium (PSf-Im), as the hydroxide conductivity of PSf-2 membrane with an IEC of 1.05 mmol g −1 was 59.5 mS·cm −1 at 60 °C while the hydroxide conductivity of PSf-Im membrane with an IEC of 1.27 mmol g −1 was 36.7 mS·cm −1 . In addition, the alkaline stability and the mechanical properties of the resultant AEMs were improved remarkably. The density functional theory (DFT) study showed that the introduction of OEG part can significantly increase the LUMO energy of functional group and then enhance the alkaline stability. [ABSTRACT FROM AUTHOR]

Exploring anion exchange membranes (AEMs) with high conductivity and satisfactory stability is very meaningful for the advancement of alkaline fuel cells. Herein, a novel class of intrinsic microporous AEMs with pendent piperazinium are systematically fabricated for alkaline fuel cell performance testing. Contorted and rigid spirobisindane backbone structure expands the free volume of AEMs, inducing broad and interconnected ion transport channels. This unique feature endows membranes a leading advantage for the efficient transmission of hydroxide ions. Consequently, the prepared membrane displays excellent normalized hydroxide conductivity of 78.99 mS g cm−1 mmol−1 at 80 °C. Meanwhile, the hydroxide conductivity degrades by only 8.3 % after treatment in 1 M NaOH for 1000 h at 80 °C. Moreover, the peak power density of H 2 /O 2 single cell employing this membrane exhibits 1.06 W cm−2 at 80 °C and the cell can preserve 93.0 % of its initial voltage after operating for 18 h. [Display omitted] • A systematic approach is developed to prepare intrinsic microporous poly (phenyl-alkane)s containing piperazinium. • The spirobisindane structure facilitates the construction of well-developed ion channels in AEMs. • The intrinsic microporous membrane shows normalized hydroxide conductivity of as high as 78.99 mS g cm−1 mmol−1. • The prepared membrane shows excellent H 2 /O 2 fuel cell performance and durability. [ABSTRACT FROM AUTHOR]

Anion exchange membrane (AEM) with high ionic conductivity and stable dimension is urgently needed to improve cost-effective anion exchange membrane fuel cells (AEMFC). In this study, a dibenzofuran-containing poly(terphenyl furan piperidinium) (QPTFP) membrane is successfully synthesized in large quantities with a yield exceeding 500 g for the purpose of large-scale AEM production. The introduction of non-rotatable dibenzofurans results in an acceptable swelling ratio of 25 % and high ionic conductivity of 155 mS cm−1 at 80 °C. It also exhibits a favorable tensile strength of 52.6 MPa and excellent alkaline stability of 2200 h at 80 °C in 1 M KOH. Furthermore, the AEMFC employing QPTFP membrane achieves remarkable peak power densities at 80 °C for H 2 –O 2 (2 W cm−2) and H 2 -Air (1.2 W cm−2), and demonstrates excellent stability of over 90 h at 70 °C and a current density of 0.2 A cm−2. [Display omitted] • Poly(aryl furan piperidinium)s are prepared for the continuous production of anion exchange membranes. • The membrane shows the highest conductivity of 155 mS cm−1 and excellent stability of >2200 h. • The fuel cell exhibits the highest peak power density of 2 W cm−2 (H 2 –O 2) and 1.3 W cm−2 (H 2 -Air). • The QPTFP-25 AEM is stabilized of fuel cell operation for 90 h at 70 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • The poly(aryl ether piperidinium) membranes are prepared by super acid catalysis with less amount of catalyst. • The membrane shows the highest conductivity of 140 mS cm−1 and excellent stability of greater than 2000 h. • The fuel cell exhibits the highest peak power density of 1.2 W cm−2. • The polymers can be easily prepared into larger widths of membranes. Poly(aryl piperidinium) is considered a promising material for the preparation of anion exchange membranes (AEM) with considerable conductivity and excellent chemical stability for anion exchange membrane fuel cells (AEMFC). In this research, we report a range of biphenyl ether-containing poly(aryl ether piperidinium) unlike previous ones to increase the conductivity of AEMs and the peak power density (PPD) of fuel cells, and the alkaline stability of ether bonds in the polymer backbone is demonstrated. All of the poly(aryl ether piperidinium) membranes possess comparable mechanical properties and inherent viscosity derived from the high activity of biphenyl ethers in superacid-catalyzed reactions, which means that large-width AEMs can be prepared. The data demonstrated that the poly (ether p-terphenyl piperidinium) (QPEPTpi-35) exhibited a conductivity of 140 mS cm−1 at 80 ℃ compared to the original poly (p-terphenyl piperidinium) (QPTPpi) membrane owning to optimized micro-phase separation structure and higher water uptake. Meanwhile, QPEPTpi-35 membrane conductivity retention is greater than 85% after immersion in 1 M KOH for 2000 h at 80 ℃. Moreover, the PPD of the QPEPTpi-35 membrane reaches 1.2 W cm−2 in H 2 /O 2 fuel cells, which is much higher than that of the QPTPpi membrane (0.51 W cm−2). The durability of MEA prepared by the catalyst-coated substrate (CCS) method manifests over 20 h under 0.2 A cm−2 at 60 °C. [ABSTRACT FROM AUTHOR]

Crosslinked poly (styrene sulfonic acid) (CrPSSA) is incorporated into sulfonated poly (ether ether ketone) (SPEEK) through the semi-interpenetrating polymer networks (sIPNs) method to improve proton conductivity of SPEEK proton exchange membranes (PEMs) at low relative humidity (RH). Thermogravimetric analysis indicates that the SPEEK/CrPSSA sIPN membrane can be stable up to 250 °C in N2. A single glass transition temperature (T g ) of the sIPN measured by differential scanning calorimetric measurements suggests good miscibility of the CrPSSA and SPEEK. At fixed RH the proton conductivity of the sIPN membranes increases as more CrPSSA is incorporated into SPEEK membranes. The sIPN membrane with 40 wt. % CrPSSA has a proton conductivity of 10−3 S cm−1 at 25% RH, which comparable to that of Nafion115 and is 2 orders of magnitude higher than that of the pristine SPEEK membranes (10−5 S cm−1 at RH 50%). The percolation threshold for proton conduction occurs at lower hydrophilic volume fractions with the increasing content of CrPSSA, suggesting different packing behavior of –SO3H groups in the SPEEK/CrPSSA sIPN membranes as compared with SPEEK and Nafion® membranes. [ABSTRACT FROM AUTHOR]

A novel amphiphilic cone-shaped inducer, tetra-quaternized tetraoctyloxycalix[4]arene (TQCX), is proposed to create continuous ionic channels in an anion exchange membrane (AEM). Via molecular dynamics simulation, it was found that four upper-rim cationic groups induce ionic aggregation via electrostatic interactions, while four lower-rim hydrophobic octyl side chains promote the clustering of hydrophobic domains via van der Waals interactions with the polymer backbone. The core cavity in TQCX introduces additional free volume to connect hydrophilic domains. At the optimal TQCX content of 3 wt%, the ionic clusters with a diameter of ∼12 nm are induced, and even linearly arranged to construct continuous ionic channels with a length up to ∼300 nm. Besides, TQCX also aggregates to form the ion-rich nanoparticles with the size of ∼500 nm, which also assist in the construction of interconnected hydroxide-conducting pathways. Consequently, hydroxide conductivity of the composite membrane yields a 70% improvement at 3 wt% TQCX over that of the pristine membrane, achieving the top level among the reported main-chain-type AEMs based on the polysulfone backbone. [Display omitted] • An amphiphilic cone-shaped TQCX is proposed to enhance micro-phase separation. • TQCX promotes ionic and hydrophobic aggregations, and also introduces free volume. • Continuous ionic channels are efficiently constructed with the length up to 300 nm. • The highest ion conductivity is achieved at 3 wt% TQCX, yielding a 70% increase. [ABSTRACT FROM AUTHOR]

Octopus-like side chains are introduced in poly(arylene piperidinium)-based alkaline anion exchange membranes (AEMs) to enhance the conductivity and stability. This type of side chain consists of a bulky rigid β-cyclodextrin (β-CD) as the "octopus head", and long flexible piperidinium ionic liquids as the "arms". The β-CD unit can enlarge internal free volume of the AEM to reduce ion transport resistance; the "arms" can interact with adjacent hydrophilic ionic groups and water, constructing continuous ion transport channels. The prepared poly(biphenyl piperidinium) AEM with "octopus" side chains at an ion exchange capacity (IEC) of 1.29 mmol g−1 exhibits higher hydroxide conductivity (121.5 mS cm−1 at 80 °C) than that without the "octopus" structure (57.4 mS cm−1) although the latter has a larger IEC (1.55 mmol g−1). This "octopus" AEM retains 87.2% of its conductivity after being treated in a 1 M NaOH at 80 °C for 480 h. The alkaline H 2 /O 2 fuel cell constructed with this "octopus" AEM produces a peak power density of 469 mW cm−2; the cell voltage can be maintained by 85% during 16 h operation. This work illustrates the advantage of "octopus" side chain for enhancement of AEM performance. [Display omitted] • Octopus-like side chains are grafted on an ether-free backbone for AEM preparation. • The octopus-type side chains can promote micro-phase separation. • The octopus side chain AEM exhibits a high hydroxide ion conductivity (121.5 mS cm−1 at 80 °C). • The H 2 –O 2 fuel cell employing the above AEM yields a power density of 469 mW cm−2 at 60 °C. [ABSTRACT FROM AUTHOR]

Anion exchange membranes (AEMs) are an important component in anion exchange membrane fuel cells, and their side chain structures have a significant impact on membrane performance. Here, we construct a series of poly(phenylene oxide) (PPO)-based AEMs with varied side chain structures and investigate the effects of alkyl or alkoxyl extenders (or "tail" of the cation) and spacers (or the link between backbone and cation head group) on AEM performance. Our investigations demonstrate that the simultaneous introduction of alkoxyl extender and spacer can significantly improve water absorption and ion conductivity of membrane; this is attributed to the good hydrophilicity of alkoxyl group and flexibility of spacer that benefit the formation hydrophilic domains. At an IEC (ion exchange capacity) of 1.13 mmol/g, the AEM containing both spacer and alkoxyl extender exhibits a hydroxide conductivity of 87.3 mS/cm (80 °C), which is much higher than that of other spacer-containing membranes at similar IECs. The H 2 /O 2 single cell constructed with this membrane exhibits a good peak power density of 292 mW/cm2 at 60 °C. In addition, the steric hindrance of the extender gives rise to higher alkali stability of the AEM than that of the membrane which does not have the extender. Our work provides a meaningful direction of side chain design which can effectively improve conductivity and alkaline stability of AEMs. Image 1 • Alkoxy extender and alkyl spacer were co-introduced into anion exchange membrane. • Alkoxy extender and alkyl spacer can synergistically improve ion conductivity and chemical stability of membrane. • The highest conductivity of 87.3 mS/cm at 80 °C was obtained at a low IEC of 1.13 mmol/g. • The H 2 –O 2 fuel cell employing the above AEM yielded a power density of 292 mW/cm2 at 60 °C. [ABSTRACT FROM AUTHOR]

N-spirocyclic cations possess double-cyclic non-planar structure that exhibit the highest alkali stability among quaternary ammonium cations, however, the extremely rigidity usually causes fragile membranes and poor conductivity. In this work, a rod-coil grafts design is proposed for N-spirocyclic anion exchange membranes (AEMs), in which microphase separation of the hydrophilic N-spirocyclic rod grafts is significantly improved by the hydrophobic aggregation of the flexible alkyl coil grafts with polysulfone backbone. Molecular dynamic simulations indicate that the coil grafts contribute to microphase separation but fill in free volume to reduce water reservoir, therefore the rod-coil grafts design provides a way to evaluate the effects of microphase separation and free volume on conductivity. The increasing conductivity with the length of coil grafts suggests a greater contribution of good microphase separation to OH− conduction. With optimized n-octylamine hydrophobic coil graft length, the N-spirocyclic AEM exhibits toughness (elongation at break of about 28.7%) and high OH− conductivity (136.2 mS cm−1 at 80 °C), resulting in high power density (850.1 mW cm−2), which is far greater than that assemble with other N-spirocyclic AEMs, and also bring N-spirocyclic AEMs into the top level of the cycloaliphatic AEMs reported in literatures. Image 1 • Rod-coil grafts for robust, high conductive and alkali stable N-spirocyclic AEMs. • Coil grafts join aggregation of hydrophobic domains to enhance microphase separation. • Microphase separation contributes greater than free volume to promote conductivity. • Highest power density is achieved among different N-spirocyclic based fuel cells. [ABSTRACT FROM AUTHOR]

Developing anion exchange membranes (AEMs) having high hydroxide conductivity, swelling resistance and excellent alkaline stability is a challenge for fuel cells now. Herein, a universal and controllable approach of grafting rigid side chain is first proposed to construct connected ion transport nano-channels. A new route is also provided to prepare AEMs with stable symmetric saturated heterocyclic amomium. The rigid side chain is introduced onto poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) by the Friedel-Crafts acylation with 4-fluorobenzoyl chloride and subsequent reaction between phenyl fluoride and secondary amine of 1-methylpiperazine. Then the terminal piperazinium is produced by the reaction between tertiary amine of 1-methylpiperazine and methyl iodide. Rigid branches expand free volume to construct connected ion transport nano-channels, leading to excellent conductivity (108 mS cm−1 at 60 °C) that is higher than those of other reported symmetric heterocyclic amomium functionalized AEMs (33–89 mS cm−1 at 60 °C). Due to the high conductivity, the H 2 /O 2 cell employing this membrane achieves one of the highest peak power densities (1210 mW cm−2 at 2600 mA cm−2) so far. In addition, the IEC of the membrane remains constant after testing in 1 M NaOH at 60 °C over 500 h. Image 1 • A novel approach was developed to construct connected ion transport nano-channels. • The membrane showed high conductivity and good alkaline stability. • The H 2 /O 2 cell with this membrane achieved high power density of 1210 mW cm−2. [ABSTRACT FROM AUTHOR]