The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Masahiro Watanabe - One of the best experts on this subject based on the ideXlab platform.
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effects of short side chain perfluorosulfonic acid Ionomers as binders on the performance of low pt loading fuel cell cathodes
Journal of Power Sources, 2015Co-Authors: Youngchul Park, Masahiro Watanabe, Katsuyoshi Kakinuma, Hiroyuki Uchida, Makoto UchidaAbstract:Abstract We investigated the effects of short-side-chain (SSC) perfluorosulfonic acid Ionomers on the electrochemical properties, fuel cell performance and ionomer distribution of a highly dispersed Pt/GCB catalyst with a low Pt loading, 0.05 mg cm−2. The SSC Ionomers in the cathode catalyst layers (CLs) resulted in an improvement of the Pt utilization (UPt) and Pt effectiveness (EfPt) values compared with those for the conventional long-side-chain (LSC) ionomer. Furthermore, the SSC Ionomers with high ion exchange capacity (IEC), e.g., SSC-1.43 and SSC-1.80 Ionomers, exhibited significantly enhanced cell performance under low to medium relative humidity (RH) conditions. This result is ascribed to the higher proton conductivity of the SSC Ionomers and more effective trapping of water that is produced during the oxygen reduction reaction (ORR) than those of the LSC ionomer. It was also found that the SSC Ionomers showed better continuity and uniformity on the Pt and carbon particles than the LSC ionomer, which might have led to improvement of both the mass transport and the proton-conducting network in the CLs. The application of the SSC Ionomers as binders demonstrated an increase of the performance at the low Pt loading fuel cell cathode over a wide range of humidity.
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synthesis and properties of anion conductive Ionomers containing fluorenyl groups for alkaline fuel cell applications
Polymer Chemistry, 2011Co-Authors: Manabu Tanaka, Masaki Koike, Kenji Miyatake, Masahiro WatanabeAbstract:A series of anion conductive aromatic Ionomers, poly(arylene ether)s containing different polymer backbones and quaternized ammonio-substituted fluorenyl groups, were synthesized via nucleophilic substitution polycondensation, chloromethylation, quaternization, and the subsequent ion exchange reactions. The ion exchange capacity (IEC) of the Ionomers was controlled to be from 0.68 to 2.54 meq. g−1 by the chloromethylation reaction conditions. The designed chemical structures were well-characterized by the 1H NMR spectra. The Ionomers provided ductile and transparent membranes. The ionomer membranes were thermally stable up to 180 °C under nitrogen and mechanically stable with 48 MPa of the maximum stress at 80 °C and 60% RH (relative humidity). High hydroxide ion conductivity up to 50 mS cm−1 was achieved at 30 °C in water for the ionomer membrane bearing sulfone/ketone structures and the highest IEC (2.54 meq. g−1). The membranes were durable in hot water (80 °C) for 1000 hours. These properties of the ionomer membranes seem promising as an anion exchange membrane for alkaline fuel cells.
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tuned polymer electrolyte membranes based on aromatic polyethers for fuel cell applications
Journal of the American Chemical Society, 2007Co-Authors: Kenji Miyatake, Yohei Chikashige, Eiji Higuchi, Masahiro WatanabeAbstract:Poly(arylene ether sulfone)-based Ionomers containing sulfofluorenyl groups have been synthesized for applications to polymer electrolyte membrane fuel cells (PEMFCs). In order to achieve high proton conductivity and chemical, mechanical, and dimensional stability, the molecular structure of the Ionomers has been optimized. Tough, flexible, and transparent membranes were obtained from a series of modified Ionomers containing methyl groups with the ion-exchange capacity (IEC) ranging from 1.32 to 3.26 meq/g. Isopropylidene tetramethylbiphenylene moieties were more effective than the methyl-substituted fluorenyl groups in giving a high-IEC ionomer membrane with substantial stability to hydrolysis and oxidation. Dimensional stability was significantly improved for the methyl-substituted ionomer membranes compared to that of the non-methylated ones. This new ionomer membrane showed comparable proton conductivity to that of the perfluorinated ionomer membrane (Nafion 112) under a wide range of conditions (80−1...
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tuned polymer electrolyte membranes based on aromatic polyethers for fuel cell applications
Journal of the American Chemical Society, 2007Co-Authors: Kenji Miyatake, Yohei Chikashige, Eiji Higuchi, Masahiro WatanabeAbstract:Poly(arylene ether sulfone)-based Ionomers containing sulfofluorenyl groups have been synthesized for applications to polymer electrolyte membrane fuel cells (PEMFCs). In order to achieve high proton conductivity and chemical, mechanical, and dimensional stability, the molecular structure of the Ionomers has been optimized. Tough, flexible, and transparent membranes were obtained from a series of modified Ionomers containing methyl groups with the ion-exchange capacity (IEC) ranging from 1.32 to 3.26 meq/g. Isopropylidene tetramethylbiphenylene moieties were more effective than the methyl-substituted fluorenyl groups in giving a high-IEC ionomer membrane with substantial stability to hydrolysis and oxidation. Dimensional stability was significantly improved for the methyl-substituted ionomer membranes compared to that of the non-methylated ones. This new ionomer membrane showed comparable proton conductivity to that of the perfluorinated ionomer membrane (Nafion 112) under a wide range of conditions (80-120 degrees C and 20-93% relative humidity (RH)). The highest proton conductivity of 0.3 S/cm was obtained at 80 degrees C and 93% RH. Although there is a decline of proton conductivity with time, after 10 000 h the proton conductivities were still at acceptable levels for fuel cell operation. The membranes retained their strength, flexibility, and high molecular weight after 10 000 h. Microscopic analyses revealed well-connected ionic clusters for the high-IEC membrane. A fuel cell operated using the polyether ionomer membrane showed better performance than that of Nafion at a low humidity of 20% RH and high temperature of 90 degrees C. Unlike the other hydrocarbon Ionomers, the present membrane showed a lower resistance than expected from its conductivity, indicating superior water-holding capability at high temperature and low humidity.
Michael R. Hibbs - One of the best experts on this subject based on the ideXlab platform.
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Non-platinum Carbon-Supported Oxygen Reduction Catalyst Ink Evaluation Based on Poly(sulfone) and Poly(phenylene)-Derived Ionomers in Alkaline Media
Electrocatalysis, 2014Co-Authors: Michael H Robson, Wendy Patterson, Kateryna Artyushkova, Plamen Atanassov, Michael R. HibbsAbstract:Described in this work is an electrochemical evaluation of novel alkaline Ionomers employed as catalyst binder for non-platinum group metal electrocatalysts based on cyanamide precursor. Electrochemical evaluation of the non-platinum group metal (non-PGM) catalyst bound with the featured alkaline ionomer classes over a range of conditions gives insight into how they behave, as well as provide information on how the varying functionalities enhance or inhibit the rate of oxygen reduction. We are showing that the polymer backbone structure has a larger influence on facilitating favorable reaction kinetics than ionomer to catalysts ratio. The poly(sulfone)-derived Ionomers result in a worse activity than electrocatalysts with Nafion® and poly(phenylene)-derived Ionomers. They also exhibited more peroxide desorption and greater limitation in the mass transport regime. The poly(phenylene)-derived polymers performed in line with the benchmark ionomer, Nafion®. The poly(phenylene)-derived Ionomers show promise as fruitful line of research in establishing an anion-conducting ionomer for alkaline electrolyte fuel cells.
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resonance stabilized perfluorinated Ionomers for alkaline membrane fuel cells
Macromolecules, 2013Co-Authors: Dae Sik Kim, Michael R. Hibbs, Cy H Fujimoto, Andrea Labouriau, Yoongkee Choe, Yu Seung KimAbstract:Perfluorosulfonic acids such as Nafion are industrial standard cation exchange Ionomers for polymer electrolyte membrane fuel cells because of their high gas permeability, hydrophobicity, and inertness to electro-chemical reaction. In this research, pentamethylguanidinium functionalized, perfluorinated hydroxide conducting Ionomers for alkaline membrane fuel cells were prepared and characterized. The alkaline stability of the Ionomers largely depended on the adjacent group that connected the cation; Sulfone guanidinium functionalized ionomer degraded almost completely after soaking in 0.5 M NaOH at 80 °C for 24 h, while phenylguanidinium functionalized ionomer did not degrade under the same conditions for 72 h. Spectroscopic data and density functional theory calculation suggested that the stability of the phenylguanidinium ionomer was greatly improved by charge delocalization of the formed resonance structure. Alkaline membrane fuel cells using the resonance stabilized perfluorinated ionomer in the catal...
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novel koh free anion exchange membrane fuel cell performance comparison of alternative anion exchange Ionomers in catalyst ink
Electrochimica Acta, 2010Co-Authors: Elise E Switzer, Michael R. Hibbs, Plamen Atanassov, Cy H Fujimoto, Tim S Olson, Abhaya K Datye, Chris J CorneliusAbstract:Alkaline membrane electrode assemblies (MEAs) were fabricated and tested in 5 cm2 single cell configuration. The fuel cell tests were preformed in the absence of any liquid electrolyte, such as KOH. This study shows fuel cell polarization curves for alkaline membrane fuel cell (AMFC) systems that were fabricated with novel anion-exchange Ionomers. A comparison of two novel anion-exchange Ionomers incorporated into the catalyst ink was achieved by comparing the performance under H2/O2 and H2/air operating conditions. The results presented here indicate that the chemical and physical properties of the recast anion-exchange ionomer that is utilized in AMFC catalyst layers directly influence the obtainable fuel cell performance. It is shown that ionomer materials that are less prone to swelling from hydration and tend to pack closely together in the solid state will result in stronger catalyst–ionomer interfacial interactions. The O2 transport properties in alkaline MEA cathodes are influenced by the resulting void volume of the electrode as defined by the structure and packing arrangement of the recast ionomer molecules.
Kenji Miyatake - One of the best experts on this subject based on the ideXlab platform.
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synthesis and properties of anion conductive Ionomers containing fluorenyl groups for alkaline fuel cell applications
Polymer Chemistry, 2011Co-Authors: Manabu Tanaka, Masaki Koike, Kenji Miyatake, Masahiro WatanabeAbstract:A series of anion conductive aromatic Ionomers, poly(arylene ether)s containing different polymer backbones and quaternized ammonio-substituted fluorenyl groups, were synthesized via nucleophilic substitution polycondensation, chloromethylation, quaternization, and the subsequent ion exchange reactions. The ion exchange capacity (IEC) of the Ionomers was controlled to be from 0.68 to 2.54 meq. g−1 by the chloromethylation reaction conditions. The designed chemical structures were well-characterized by the 1H NMR spectra. The Ionomers provided ductile and transparent membranes. The ionomer membranes were thermally stable up to 180 °C under nitrogen and mechanically stable with 48 MPa of the maximum stress at 80 °C and 60% RH (relative humidity). High hydroxide ion conductivity up to 50 mS cm−1 was achieved at 30 °C in water for the ionomer membrane bearing sulfone/ketone structures and the highest IEC (2.54 meq. g−1). The membranes were durable in hot water (80 °C) for 1000 hours. These properties of the ionomer membranes seem promising as an anion exchange membrane for alkaline fuel cells.
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tuned polymer electrolyte membranes based on aromatic polyethers for fuel cell applications
Journal of the American Chemical Society, 2007Co-Authors: Kenji Miyatake, Yohei Chikashige, Eiji Higuchi, Masahiro WatanabeAbstract:Poly(arylene ether sulfone)-based Ionomers containing sulfofluorenyl groups have been synthesized for applications to polymer electrolyte membrane fuel cells (PEMFCs). In order to achieve high proton conductivity and chemical, mechanical, and dimensional stability, the molecular structure of the Ionomers has been optimized. Tough, flexible, and transparent membranes were obtained from a series of modified Ionomers containing methyl groups with the ion-exchange capacity (IEC) ranging from 1.32 to 3.26 meq/g. Isopropylidene tetramethylbiphenylene moieties were more effective than the methyl-substituted fluorenyl groups in giving a high-IEC ionomer membrane with substantial stability to hydrolysis and oxidation. Dimensional stability was significantly improved for the methyl-substituted ionomer membranes compared to that of the non-methylated ones. This new ionomer membrane showed comparable proton conductivity to that of the perfluorinated ionomer membrane (Nafion 112) under a wide range of conditions (80−1...
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tuned polymer electrolyte membranes based on aromatic polyethers for fuel cell applications
Journal of the American Chemical Society, 2007Co-Authors: Kenji Miyatake, Yohei Chikashige, Eiji Higuchi, Masahiro WatanabeAbstract:Poly(arylene ether sulfone)-based Ionomers containing sulfofluorenyl groups have been synthesized for applications to polymer electrolyte membrane fuel cells (PEMFCs). In order to achieve high proton conductivity and chemical, mechanical, and dimensional stability, the molecular structure of the Ionomers has been optimized. Tough, flexible, and transparent membranes were obtained from a series of modified Ionomers containing methyl groups with the ion-exchange capacity (IEC) ranging from 1.32 to 3.26 meq/g. Isopropylidene tetramethylbiphenylene moieties were more effective than the methyl-substituted fluorenyl groups in giving a high-IEC ionomer membrane with substantial stability to hydrolysis and oxidation. Dimensional stability was significantly improved for the methyl-substituted ionomer membranes compared to that of the non-methylated ones. This new ionomer membrane showed comparable proton conductivity to that of the perfluorinated ionomer membrane (Nafion 112) under a wide range of conditions (80-120 degrees C and 20-93% relative humidity (RH)). The highest proton conductivity of 0.3 S/cm was obtained at 80 degrees C and 93% RH. Although there is a decline of proton conductivity with time, after 10 000 h the proton conductivities were still at acceptable levels for fuel cell operation. The membranes retained their strength, flexibility, and high molecular weight after 10 000 h. Microscopic analyses revealed well-connected ionic clusters for the high-IEC membrane. A fuel cell operated using the polyether ionomer membrane showed better performance than that of Nafion at a low humidity of 20% RH and high temperature of 90 degrees C. Unlike the other hydrocarbon Ionomers, the present membrane showed a lower resistance than expected from its conductivity, indicating superior water-holding capability at high temperature and low humidity.
Karen I Winey - One of the best experts on this subject based on the ideXlab platform.
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Ionomers from step growth polymerization highly ordered ionic aggregates and ion conduction
Macromolecules, 2020Co-Authors: Lu Yan, Lauren Hoang, Karen I WineyAbstract:Precisely controlling the position of ionic groups along neutral polymer backbones in Ionomers has led to novel nanoscale morphologies and promising properties, although the synthetic routes can be quite demanding. Here, we report a series of Li+-containing Ionomers directly synthesized from step-growth polymerization of commercially available diol monomers (x = 6 or 12) and dianhydride monomers followed by neutralization with various amounts of lithium salts. The results are nearly precise linear polymers wherein nonpolar segments have precisely 6 or 12 methylene groups, as determined by the diol. The functional segment has two carboxylic acid pendant groups and 6–8 backbone atoms depending on the dianhydride addition. From X-ray scattering, these segmented Ionomers exhibit well-defined nanostructures in contrast to the conventional random Ionomers. The nearly precise nature of these segmented Ionomers does not compromise the morphological ordering. The temperature-dependent ionic conductivities exhibit ...
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ionic aggregate structure in ionomer melts effect of molecular architecture on aggregates and the ionomer peak
Journal of the American Chemical Society, 2012Co-Authors: Lisa M Hall, Michelle E Seitz, Mark J Stevens, Kathleen L. Opper, Karen I Winey, Kenneth B Wagener, Amalie L FrischknechtAbstract:We perform a comprehensive set of coarse-grained molecular dynamics simulations of ionomer melts with varying polymer architectures and compare the results to experiments in order to understand ionic aggregation on a molecular level. The model Ionomers contain periodically or randomly spaced charged beads, placed either within or pendant to the polymer backbone, with the counterions treated explicitly. The ionic aggregate structure was determined as a function of the spacing of charged beads and also depends on whether the charged beads are in the polymer backbone or pendant to the backbone. The low wavevector ionomer peak in the counterion scattering is observed for all systems, and it is sharpest for Ionomers with periodically spaced pendant charged beads with a large spacing between charged beads. Changing to a random or a shorter spacing moves the peak to lower wavevector. We present new experimental X-ray scattering data on Na+-neutralized poly(ethylene-co-acrylic acid) Ionomers that show the same tw...
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nanoscale morphology in precisely sequenced poly ethylene co acrylic acid zinc Ionomers
Journal of the American Chemical Society, 2010Co-Authors: Michelle E Seitz, Kathleen L. Opper, Kenneth B Wagener, Christopher D Chan, Travis W Baughman, Karen I WineyAbstract:The morphology of a series of linear poly(ethylene-co-acrylic acid) zinc-neutralized Ionomers with either precisely or randomly spaced acid groups was investigated using X-ray scattering, differential scanning calorimetry (DSC), and scanning transmission electron microscopy (STEM). Scattering from semicrystalline, precise Ionomers has contributions from acid layers associated with the crystallites and ionic aggregates dispersed in the amorphous phase. The precisely controlled acid spacing in these Ionomers reduces the polydispersity in the aggregate correlation length and yields more intense, well-defined scattering peaks. Remarkably, the ionic aggregates in an amorphous, precise ionomer with 22 mol % acid and 66% neutralization adopt a cubic lattice; this is the first report of ionic aggregate self-assembly onto a lattice in an ionomer with an all-carbon backbone. Aggregate size is insensitive to acid content or neutralization level. As the acid content increases from 9.5 to 22 mol % at ∼75% neutralizati...
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multi length scale morphology of poly ethylene oxide based sulfonate Ionomers with alkali cations at room temperature
Macromolecules, 2010Co-Authors: Wenqin Wang, Ralph H Colby, Wenjuan Liu, Gregory J Tudryn, Karen I WineyAbstract:A series of Li-, Na-, and Cs-neutralized polyester Ionomers with well-defined poly(ethylene oxide) (PEO) spacer lengths between sulfonated phthalates have been investigated by X-ray scattering at room temperature. As the spacer lengths are increased the PEO segments crystallize, as evidenced by multiple crystal reflections that are identical to those of pure poly(ethylene glycol) oligomers. This crystallization also produces multiple small-angle peaks, which correspond to the well-defined thickness of PEO crystallites. The ionomer peak (q = 1−5 nm−1) is absent in the Na- and Cs-neutralized Ionomers, while the Li-neutralized Ionomers show peaks at q = 2−3 nm−1, reminiscent of conventional ionic aggregates in Ionomers. Detailed analysis of the normalized X-ray scattering intensity from these Ionomers reveals a variety of ionic states that are highly dependent on the cation size. The states of ionic groups change from a majority of isolated ion pairs to aggregated structures as the cation size decreases from...
Nanwen Li - One of the best experts on this subject based on the ideXlab platform.
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effect of n cyclic cationic groups in poly phenylene oxide based catalyst ionomer membranes for anion exchange membrane fuel cells
Journal of Membrane Science, 2020Co-Authors: Hyun Park, Daeil Choi, Jae Woo Jung, Sae Yane Baek, Yongchae Chung, Jong Geun Seong, Nanwen LiAbstract:Abstract Herein, as a binder (or catalyst ionomer) for AEMFCs, we investigated the effect of two different cationic copolymers based on poly(phenylene oxide) (PPO) with N-cyclic quaternary ammonium (QA) groups, including six-membered dimethyl piperidinium (DMP) and bis-six-membered azonia-spiro undecane (ASU). An earlier report on the same polymers for membranes in AEMFCs indicated the better electrochemical performance of PPO-ASU compared with PPO-DMP. Therefore, we would like to investigate these two polymers for catalyst Ionomers. The outcome in this study using these two copolymers as catalyst Ionomers indicates the opposite result; the electrochemical performance of the PPO-DMP ionomer is much better than the PPO-ASU ionomer. The commercial Fumion ionomer was used for the qualitative comparison. The density functional theory (DFT) calculation of the adsorption energy according to different orientations of the cationic groups on the catalyst surface shows that there is no difference between the adsorption energy of DMP and ASU cations, in compliance with the orientations of the cations. Although the PPO-ASU ionomer membrane has the highest hydroxide conductivity at 60 °C in liquid water, the hydrogen oxidation/reduction (HOR) activity of PPO-DMP and PPO-ASU showed similar values with the Fumion ionomer. While the PPO-DMP ionomer membrane shows relatively large fuel gas (hydrogen) permeability in dry and wet conditions, due to the chain flexibility and the presence of two methyl groups compared to the single methyl groups and lower flexibility of the PPO-ASU and Fumion Ionomers. The electrochemical performance of a membrane electrode assembly (MEA) using the PPO-DMP ionomer exhibited an exceptional peak power density of 335 mW cm−2 compared to lower peak power densities the of PPO-ASU and Fumion Ionomers under 60 °C and a fully humidified condition (H2/O2). The SEM images of MEAs after testing supports the conclusion that the PPO-DMP ionomer forms a uniform catalyst interface that is very well bound between the electrode and membrane, unlike the PPO-ASU and Fumion Ionomers. The PPO-DMP ionomer membrane also showed better tensile strength and elongation at break than the PPO-ASU ionomer membrane. Therefore, we conclude that the well-prepared three-phase boundary structure played a critical role for the catalyst ionomer in each electrode, overcoming one of the critical performance-limiting factors.