The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
James M Fenton - One of the best experts on this subject based on the ideXlab platform.
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Low Equivalent Weight Friedel-Crafts cross-linked sulfonated poly(ether ether ketone)
Journal of Membrane Science, 2020Co-Authors: Stephen L.n.h. Rhoden, Clovis A Linkous, Nahid Mohajeri, Diego J Diaz, Paul Brooker, Darlene K Slattery, James M FentonAbstract:false2016-03-16T16:38:26
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low Equivalent Weight friedel crafts cross linked sulfonated poly ether ether ketone
Journal of Membrane Science, 2011Co-Authors: Stephen L Rhoden, Clovis A Linkous, Nahid Mohajeri, Diego J Diaz, Paul Brooker, Darlene K Slattery, James M FentonAbstract:Abstract Poly(ether ether ketone) (PEEK) was sulfonated by electrophillic aromatic substitution to produce a highly water soluble polymer. With an Equivalent Weight (EW) of 381 g/eq, the polymer is capable of a proton conductivity of 0.2 S/cm at 80 °C and 100% relative humidity (RH). High proton conductivity in polymer electrolyte membranes is a key factor for optimum hydrogen fuel cell performance. Under testing at saturating RHs, the highly sulfonated polymer absorbs water while simultaneously becoming swollen and mechanically weak. To maintain mechanical stability, a ZnCl2 catalyst was used to catalyze a Friedel-Crafts-type cross-linking using benzenedimethanol(BDM) as cross-linking agent. Although membrane thermal properties did not improve substantially, solubility was decreased and mechanical strength increased. Membranes cross-linked with 12 and 24 wt.% BDM yielded polymers with Equivalent Weights of 395 and 416 g/eq and conductivities of 0.15 and 0.14 S/cm at 80 °C and 100% RH, respectively, without excessive water uptake shown by the pure 96% sulfonated PEEK. Characterization of the pure and cross-linked membranes were also studied using Fourier transform infrared spectroscopy, water uptake, thermogravimetric coupled mass spectrometry and differential scanning calorimetry. Membranes were covered with platinum on carbon catalyst ink, and further characterized using linear sweep voltammetry. Behavior comparable to perfluoroalkyl sulfonate ionomers was demonstrated.
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effect of Equivalent Weight of phosphotungstic acid incorporated composite membranes on the high temperature operation of pem fuel cells
Meeting Abstracts, 2008Co-Authors: Pyoungho Choi, Nahid Mohajeri, Darlene K Slattery, Leonard J Bonville, Marianne P Rodgers, Benjamin P Pearman, Bo Li, Rohit Agarwal, H R Kunz, James M FentonAbstract:Fuel cells have shown great promise for future power sources and there has been substantial advancement in the technology of fuel cells over the past decades. For automobile application, however, there are still challenging issues related to its performance and durability. It is highly desirable to operate fuel cells at high temperature because of a number of benefits, e.g., improved reaction kinetics and carbon monoxide tolerance. Since the conventional polymer electrolytes such as Nafion are not stable at high temperatures, the development of novel membranes that are mechanically, thermally, and electrochemically stable at high temperatures while providing good conductivity under low relative humidity condition is one of the most challenging areas of research for automobile applications of fuel cells. In fact, extensive research efforts have been made to design new proton exchange materials that can overcome the limitations of conventional polymer electrolytes.
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improving pemfc performance using low Equivalent Weight pfsa ionomers and pt co c catalyst in the cathode
Journal of The Electrochemical Society, 2007Co-Authors: Hui Xu, Russell H Kunz, Leonard J Bonville, James M FentonAbstract:The effects of lower Equivalent Weight (EW) perfluorosulfonic acid (PFSA) ionomers and Pt-Co/C catalyst on the cathode performance of proton exchange membrane fuel cells (PEMFCs) were investigated at two atmospheric pressure operating conditions: low temperature/high relative humidity (RH), 80°C/100% RH, and high temperature/low RH, 120°C/35% RH. Cell voltage at a current density of 400 mA/cm 2 was used for the performance comparison. The optimized content in the electrode changed with the ionomer EW, from 32% for 1100 EW Nafion, 28% for 920 EW Nafion to 25% for a developmental PFSA 800 EW ionomer. Compared to 1100 EW Nafion, 800 EW ionomer significantly improved the cell performance by 39 mV at 120°C/35% RH; however, at 80°C/100% RH, its effect was not apparent. The introduction of Pt-Co/C catalyst into the cathode increased the cell performance by 43 mV at 80°C/100% RH, which was much higher than a performance improvement at 120°C/35% RH. Compared to electrodes made of Pt/C and Nafion 1100 EW, the combination of 800 EW Ionomer and Pt-Co/C catalyst resulted in a 55 mV cell voltage increase at 80°C/100% RH and a 48 mV cell voltage increase at 120°C/35% RH.
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Improving PEMFC Performance Using Low Equivalent Weight PFSA Ionomers and Pt-Co ∕ C Catalyst in the Cathode
Journal of The Electrochemical Society, 2007Co-Authors: Hui Xu, Leonard J Bonville, H. Russell Kunz, James M FentonAbstract:The effects of lower Equivalent Weight (EW) perfluorosulfonic acid (PFSA) ionomers and Pt-Co/C catalyst on the cathode performance of proton exchange membrane fuel cells (PEMFCs) were investigated at two atmospheric pressure operating conditions: low temperature/high relative humidity (RH), 80°C/100% RH, and high temperature/low RH, 120°C/35% RH. Cell voltage at a current density of 400 mA/cm 2 was used for the performance comparison. The optimized content in the electrode changed with the ionomer EW, from 32% for 1100 EW Nafion, 28% for 920 EW Nafion to 25% for a developmental PFSA 800 EW ionomer. Compared to 1100 EW Nafion, 800 EW ionomer significantly improved the cell performance by 39 mV at 120°C/35% RH; however, at 80°C/100% RH, its effect was not apparent. The introduction of Pt-Co/C catalyst into the cathode increased the cell performance by 43 mV at 80°C/100% RH, which was much higher than a performance improvement at 120°C/35% RH. Compared to electrodes made of Pt/C and Nafion 1100 EW, the combination of 800 EW Ionomer and Pt-Co/C catalyst resulted in a 55 mV cell voltage increase at 80°C/100% RH and a 48 mV cell voltage increase at 120°C/35% RH.
Darlene K Slattery - One of the best experts on this subject based on the ideXlab platform.
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Low Equivalent Weight Friedel-Crafts cross-linked sulfonated poly(ether ether ketone)
Journal of Membrane Science, 2020Co-Authors: Stephen L.n.h. Rhoden, Clovis A Linkous, Nahid Mohajeri, Diego J Diaz, Paul Brooker, Darlene K Slattery, James M FentonAbstract:false2016-03-16T16:38:26
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effect of perfluorosulfonic acid membrane Equivalent Weight on degradation under accelerated stress conditions
Electrochimica Acta, 2013Co-Authors: Marianne P Rodgers, Nahid Mohajeri, Leonard J Bonville, Benjamin P Pearman, Darlene K SlatteryAbstract:Abstract The Equivalent Weight of proton exchange membranes has a large effect on their properties and can impact performance and durability in hydrogen fuel cells. For example, increasing the EW increases the crystallinity of perfluorosulfonic acid membranes, while water content and glass transition temperature decrease. The length of the sulfonic acid side chain also impacts membrane properties. Perfluorosulfonic acid membranes with shorter sulfonic acid side chains, though they exhibit similar gas permeability, have been shown to have higher crystallinity, higher glass transition temperature, slightly lower water content, and lower proton conductivity than membranes with longer sulfonic acid side chains for a given EW. Although many reports have investigated cell performance for membranes as a function of low EW and side chains length, their impact on cell durability is not well understood. Because side chain attack by radicals formed during fuel cell operation is a major source of membrane degradation, it is reasonable to hypothesize that membranes with lower EW and, therefore, more sulfonic acid side chains, would have lower durability. This study evaluates membrane degradation for cells containing PFSA membranes with 750 EW, 950 EW, and 1100 EW. The 750 EW membrane contained short sulfonic acid side-chains while the 950 EW and 1100 EW membranes were Nafion ® -based with long sulfonic acid side-chains. Membranes were tested in fuel cells for 100 h under open circuit voltage, at 90 °C and 30% relative humidity. Diagnostic tests conducted on the cells included hydrogen crossover, fluoride emission, catalyst electrochemical surface area, posttest membrane scanning electron microscopy/transmission electron microscopy evaluation, and defect identification in membranes. The 950 EW cell had the highest decay metrics including fluoride emission, voltage decay, loss in ECA, and loss in cell performance. In all cases, the 1100 EW cell showed the lowest degradation. This has been explained in terms of the lower water content and number of side-chains in the 1100 EW polymer and the absence of a tertiary carbon and lower concentration of ether linkages in the side-chains of the 750 EW polymer. To reach optimal levels of durability and performance, it is necessary to use the appropriate EW and side-chain length combination.
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low Equivalent Weight friedel crafts cross linked sulfonated poly ether ether ketone
Journal of Membrane Science, 2011Co-Authors: Stephen L Rhoden, Clovis A Linkous, Nahid Mohajeri, Diego J Diaz, Paul Brooker, Darlene K Slattery, James M FentonAbstract:Abstract Poly(ether ether ketone) (PEEK) was sulfonated by electrophillic aromatic substitution to produce a highly water soluble polymer. With an Equivalent Weight (EW) of 381 g/eq, the polymer is capable of a proton conductivity of 0.2 S/cm at 80 °C and 100% relative humidity (RH). High proton conductivity in polymer electrolyte membranes is a key factor for optimum hydrogen fuel cell performance. Under testing at saturating RHs, the highly sulfonated polymer absorbs water while simultaneously becoming swollen and mechanically weak. To maintain mechanical stability, a ZnCl2 catalyst was used to catalyze a Friedel-Crafts-type cross-linking using benzenedimethanol(BDM) as cross-linking agent. Although membrane thermal properties did not improve substantially, solubility was decreased and mechanical strength increased. Membranes cross-linked with 12 and 24 wt.% BDM yielded polymers with Equivalent Weights of 395 and 416 g/eq and conductivities of 0.15 and 0.14 S/cm at 80 °C and 100% RH, respectively, without excessive water uptake shown by the pure 96% sulfonated PEEK. Characterization of the pure and cross-linked membranes were also studied using Fourier transform infrared spectroscopy, water uptake, thermogravimetric coupled mass spectrometry and differential scanning calorimetry. Membranes were covered with platinum on carbon catalyst ink, and further characterized using linear sweep voltammetry. Behavior comparable to perfluoroalkyl sulfonate ionomers was demonstrated.
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effect of Equivalent Weight of phosphotungstic acid incorporated composite membranes on the high temperature operation of pem fuel cells
Meeting Abstracts, 2008Co-Authors: Pyoungho Choi, Nahid Mohajeri, Darlene K Slattery, Leonard J Bonville, Marianne P Rodgers, Benjamin P Pearman, Bo Li, Rohit Agarwal, H R Kunz, James M FentonAbstract:Fuel cells have shown great promise for future power sources and there has been substantial advancement in the technology of fuel cells over the past decades. For automobile application, however, there are still challenging issues related to its performance and durability. It is highly desirable to operate fuel cells at high temperature because of a number of benefits, e.g., improved reaction kinetics and carbon monoxide tolerance. Since the conventional polymer electrolytes such as Nafion are not stable at high temperatures, the development of novel membranes that are mechanically, thermally, and electrochemically stable at high temperatures while providing good conductivity under low relative humidity condition is one of the most challenging areas of research for automobile applications of fuel cells. In fact, extensive research efforts have been made to design new proton exchange materials that can overcome the limitations of conventional polymer electrolytes.
Nahid Mohajeri - One of the best experts on this subject based on the ideXlab platform.
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Low Equivalent Weight Friedel-Crafts cross-linked sulfonated poly(ether ether ketone)
Journal of Membrane Science, 2020Co-Authors: Stephen L.n.h. Rhoden, Clovis A Linkous, Nahid Mohajeri, Diego J Diaz, Paul Brooker, Darlene K Slattery, James M FentonAbstract:false2016-03-16T16:38:26
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effect of perfluorosulfonic acid membrane Equivalent Weight on degradation under accelerated stress conditions
Electrochimica Acta, 2013Co-Authors: Marianne P Rodgers, Nahid Mohajeri, Leonard J Bonville, Benjamin P Pearman, Darlene K SlatteryAbstract:Abstract The Equivalent Weight of proton exchange membranes has a large effect on their properties and can impact performance and durability in hydrogen fuel cells. For example, increasing the EW increases the crystallinity of perfluorosulfonic acid membranes, while water content and glass transition temperature decrease. The length of the sulfonic acid side chain also impacts membrane properties. Perfluorosulfonic acid membranes with shorter sulfonic acid side chains, though they exhibit similar gas permeability, have been shown to have higher crystallinity, higher glass transition temperature, slightly lower water content, and lower proton conductivity than membranes with longer sulfonic acid side chains for a given EW. Although many reports have investigated cell performance for membranes as a function of low EW and side chains length, their impact on cell durability is not well understood. Because side chain attack by radicals formed during fuel cell operation is a major source of membrane degradation, it is reasonable to hypothesize that membranes with lower EW and, therefore, more sulfonic acid side chains, would have lower durability. This study evaluates membrane degradation for cells containing PFSA membranes with 750 EW, 950 EW, and 1100 EW. The 750 EW membrane contained short sulfonic acid side-chains while the 950 EW and 1100 EW membranes were Nafion ® -based with long sulfonic acid side-chains. Membranes were tested in fuel cells for 100 h under open circuit voltage, at 90 °C and 30% relative humidity. Diagnostic tests conducted on the cells included hydrogen crossover, fluoride emission, catalyst electrochemical surface area, posttest membrane scanning electron microscopy/transmission electron microscopy evaluation, and defect identification in membranes. The 950 EW cell had the highest decay metrics including fluoride emission, voltage decay, loss in ECA, and loss in cell performance. In all cases, the 1100 EW cell showed the lowest degradation. This has been explained in terms of the lower water content and number of side-chains in the 1100 EW polymer and the absence of a tertiary carbon and lower concentration of ether linkages in the side-chains of the 750 EW polymer. To reach optimal levels of durability and performance, it is necessary to use the appropriate EW and side-chain length combination.
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low Equivalent Weight friedel crafts cross linked sulfonated poly ether ether ketone
Journal of Membrane Science, 2011Co-Authors: Stephen L Rhoden, Clovis A Linkous, Nahid Mohajeri, Diego J Diaz, Paul Brooker, Darlene K Slattery, James M FentonAbstract:Abstract Poly(ether ether ketone) (PEEK) was sulfonated by electrophillic aromatic substitution to produce a highly water soluble polymer. With an Equivalent Weight (EW) of 381 g/eq, the polymer is capable of a proton conductivity of 0.2 S/cm at 80 °C and 100% relative humidity (RH). High proton conductivity in polymer electrolyte membranes is a key factor for optimum hydrogen fuel cell performance. Under testing at saturating RHs, the highly sulfonated polymer absorbs water while simultaneously becoming swollen and mechanically weak. To maintain mechanical stability, a ZnCl2 catalyst was used to catalyze a Friedel-Crafts-type cross-linking using benzenedimethanol(BDM) as cross-linking agent. Although membrane thermal properties did not improve substantially, solubility was decreased and mechanical strength increased. Membranes cross-linked with 12 and 24 wt.% BDM yielded polymers with Equivalent Weights of 395 and 416 g/eq and conductivities of 0.15 and 0.14 S/cm at 80 °C and 100% RH, respectively, without excessive water uptake shown by the pure 96% sulfonated PEEK. Characterization of the pure and cross-linked membranes were also studied using Fourier transform infrared spectroscopy, water uptake, thermogravimetric coupled mass spectrometry and differential scanning calorimetry. Membranes were covered with platinum on carbon catalyst ink, and further characterized using linear sweep voltammetry. Behavior comparable to perfluoroalkyl sulfonate ionomers was demonstrated.
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effect of Equivalent Weight of phosphotungstic acid incorporated composite membranes on the high temperature operation of pem fuel cells
Meeting Abstracts, 2008Co-Authors: Pyoungho Choi, Nahid Mohajeri, Darlene K Slattery, Leonard J Bonville, Marianne P Rodgers, Benjamin P Pearman, Bo Li, Rohit Agarwal, H R Kunz, James M FentonAbstract:Fuel cells have shown great promise for future power sources and there has been substantial advancement in the technology of fuel cells over the past decades. For automobile application, however, there are still challenging issues related to its performance and durability. It is highly desirable to operate fuel cells at high temperature because of a number of benefits, e.g., improved reaction kinetics and carbon monoxide tolerance. Since the conventional polymer electrolytes such as Nafion are not stable at high temperatures, the development of novel membranes that are mechanically, thermally, and electrochemically stable at high temperatures while providing good conductivity under low relative humidity condition is one of the most challenging areas of research for automobile applications of fuel cells. In fact, extensive research efforts have been made to design new proton exchange materials that can overcome the limitations of conventional polymer electrolytes.
Stephen L Rhoden - One of the best experts on this subject based on the ideXlab platform.
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low Equivalent Weight friedel crafts cross linked sulfonated poly ether ether ketone
Journal of Membrane Science, 2011Co-Authors: Stephen L Rhoden, Clovis A Linkous, Nahid Mohajeri, Diego J Diaz, Paul Brooker, Darlene K Slattery, James M FentonAbstract:Abstract Poly(ether ether ketone) (PEEK) was sulfonated by electrophillic aromatic substitution to produce a highly water soluble polymer. With an Equivalent Weight (EW) of 381 g/eq, the polymer is capable of a proton conductivity of 0.2 S/cm at 80 °C and 100% relative humidity (RH). High proton conductivity in polymer electrolyte membranes is a key factor for optimum hydrogen fuel cell performance. Under testing at saturating RHs, the highly sulfonated polymer absorbs water while simultaneously becoming swollen and mechanically weak. To maintain mechanical stability, a ZnCl2 catalyst was used to catalyze a Friedel-Crafts-type cross-linking using benzenedimethanol(BDM) as cross-linking agent. Although membrane thermal properties did not improve substantially, solubility was decreased and mechanical strength increased. Membranes cross-linked with 12 and 24 wt.% BDM yielded polymers with Equivalent Weights of 395 and 416 g/eq and conductivities of 0.15 and 0.14 S/cm at 80 °C and 100% RH, respectively, without excessive water uptake shown by the pure 96% sulfonated PEEK. Characterization of the pure and cross-linked membranes were also studied using Fourier transform infrared spectroscopy, water uptake, thermogravimetric coupled mass spectrometry and differential scanning calorimetry. Membranes were covered with platinum on carbon catalyst ink, and further characterized using linear sweep voltammetry. Behavior comparable to perfluoroalkyl sulfonate ionomers was demonstrated.
Clovis A Linkous - One of the best experts on this subject based on the ideXlab platform.
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Low Equivalent Weight Friedel-Crafts cross-linked sulfonated poly(ether ether ketone)
Journal of Membrane Science, 2020Co-Authors: Stephen L.n.h. Rhoden, Clovis A Linkous, Nahid Mohajeri, Diego J Diaz, Paul Brooker, Darlene K Slattery, James M FentonAbstract:false2016-03-16T16:38:26
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low Equivalent Weight friedel crafts cross linked sulfonated poly ether ether ketone
Journal of Membrane Science, 2011Co-Authors: Stephen L Rhoden, Clovis A Linkous, Nahid Mohajeri, Diego J Diaz, Paul Brooker, Darlene K Slattery, James M FentonAbstract:Abstract Poly(ether ether ketone) (PEEK) was sulfonated by electrophillic aromatic substitution to produce a highly water soluble polymer. With an Equivalent Weight (EW) of 381 g/eq, the polymer is capable of a proton conductivity of 0.2 S/cm at 80 °C and 100% relative humidity (RH). High proton conductivity in polymer electrolyte membranes is a key factor for optimum hydrogen fuel cell performance. Under testing at saturating RHs, the highly sulfonated polymer absorbs water while simultaneously becoming swollen and mechanically weak. To maintain mechanical stability, a ZnCl2 catalyst was used to catalyze a Friedel-Crafts-type cross-linking using benzenedimethanol(BDM) as cross-linking agent. Although membrane thermal properties did not improve substantially, solubility was decreased and mechanical strength increased. Membranes cross-linked with 12 and 24 wt.% BDM yielded polymers with Equivalent Weights of 395 and 416 g/eq and conductivities of 0.15 and 0.14 S/cm at 80 °C and 100% RH, respectively, without excessive water uptake shown by the pure 96% sulfonated PEEK. Characterization of the pure and cross-linked membranes were also studied using Fourier transform infrared spectroscopy, water uptake, thermogravimetric coupled mass spectrometry and differential scanning calorimetry. Membranes were covered with platinum on carbon catalyst ink, and further characterized using linear sweep voltammetry. Behavior comparable to perfluoroalkyl sulfonate ionomers was demonstrated.