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Young Moo Lee - One of the best experts on this subject based on the ideXlab platform.
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durable Sulfonated Poly arylene sulfide sulfone nitrile s containing naphthalene units for direct methanol fuel cells dmfcs
Macromolecules, 2013Co-Authors: Dong Won Shin, Michael D Guiver, So Young Lee, Na Rae Kang, Kang Hyuck Lee, Young Moo LeeAbstract:Sulfonated Poly(arylene sulfide sulfone nitrile)s (SN) were synthesized to investigate the effects of naphthalene units in the Polymer backbone on membrane properties. The small and planar naphthalene in the main chain reduced interdomain distance, as confirmed by molecular simulations and small-angle X-ray scattering patterns. The SN Polymer membranes exhibited excellent chemical and mechanical properties, better than those of their phenylene counterpart (SP). In particular, the water uptake and swelling ratio of the SN membranes were much lower than those of the SP membranes. Furthermore, the SN membranes exhibited a greatly reduced methanol permeability ((9–17) × 10–8 cm2 s–1) compared to Nafion 212 (330 × 10–8 cm2 s–1) at 30 °C in 10 M methanol. Moreover, sulfide- and naphthalene-based chemical structure of the SN membranes enhanced their DMFC single cell performance and long-term stability during fuel cell operation.
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morphological transformation during cross linking of a highly Sulfonated Poly phenylene sulfide nitrile random coPolymer
Energy and Environmental Science, 2012Co-Authors: So Young Lee, Chang Hyun Lee, Michael D Guiver, Na Rae Kang, Dong Won Shin, Kwansoo Lee, Young Moo LeeAbstract:We present a new approach of morphological transformation for effective proton transport within ionomers, even at partially hydrated states. Highly Sulfonated Poly(phenylene sulfide nitrile) (XESPSN) random network coPolymers were synthesized as alternatives to state-of-the-art perfluorinated Polymers such as Nafion®. A combination of thermal annealing and cross-linking, which was conducted at 250 °C by simple trimerisation of ethynyl groups at the chain termini, results in a morphological transformation. The resulting nanophase separation between the hydrophilic and hydrophobic domains forms well-connected hydrophilic nanochannels for dramatically enhanced proton conduction, even at partially hydrated conditions. For instance, the proton conductivity of XESPSN60 was 160% higher than that of Nafion® 212 at 80 °C and 50% relative humidity. The water uptake and dimensional swelling were also reduced and mechanical properties and oxidative stability were improved after three-dimensional network formation. The fuel cell performance of XESPSN membranes exhibited a significantly higher maximum power density than that of Nafion® 212 under partially hydrated environments.
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direct surface fluorination of Sulfonated Poly phenylene sulfide sulfone nitrile spssn membrane for high performance fuel cell
Meeting Abstracts, 2010Co-Authors: So Young Lee, Chi Hoon Park, Na Rae Kang, Dong Won Shin, Doo Sung Hwang, Young Moo LeeAbstract:he proton exchange membrane (PEM) is one of the key components in fuel cell systems. The important technical focus is on developing PEMs, which are able to exhibit high proton conductivity, low fuel permeability and reduced water uptake. The perfluoro Sulfonated membranes such as Nafion have been widely used because of its high resistance to chemical attack as well as high proton conductivity in the Polymer backbone. However, they have disadvantages such as low thermal stability due to their low Tg and high reactant permeablility. Up to now, much efforts have been put into the development of novel Sulfonated aromatic hydrocarbon Polymer membranes to overcome drawbacks of Nafion. We have already reported on the novel Sulfonated Poly (phenylene sulfide sulfone nitrile) (SPSSN). The thioether group was introduced to increase the hydrolytic and oxidative stability and excellent thermal stability, even at 120C. Moreover nitrile groups in the backbone were added, which play an important role in reducing water uptake and dimensional swelling without siginificant proton conductivity loss. In this study, we investigate surface modification of Sulfonated Poly(phenylene sulfide sulfone nitrile)(SPSSN) membrane by using direct fluorination. Surface fluorination treatments convert some C-H into C-F bonds on the membrane surface. In particular, the surface enrichment of fluorine atoms led to anisotropic swelling behavior, associated with stable electrode interface formation. Strikingly random coPolymer as a Polymer matrix showed, the low surface free energy of the C-F bonds induced a well difined continuous ionic channel structure, similar to those of multiblock coPolymer. Therefore, surface fluorinated SPSSN membranes were expected to improve proton conductivity, reduce water uptake and increase high dimensional stability compared to pristine membrane due to the synergy effect of -CNgroup. Experimental Sulfonated Poly(phenylene sulfide sulfone nitrile) random Polymer (SPSSN) were synthesized as previously reported. SPSSN membrane with an average thickness of 60 μm was obtained after casting a 15 wt% solution on the glass plate, and drying in a vacuum oven. Then, the membrane was acidified by 1M H2SO4 boiling solution for 4 hours and washed in boiling water for 4 hours. Surface fluorinated SPSSN membranes were prepared by dilute fluorine gas (500 ppm F2/N2 at atmospheric pressure) at 25 C for 10, 30, and 60 minutes in a reaction chamber. The degree of fluorination was same on both sides of the membranes. The successful surface fluorination of SPSSN was confirmed via ESCA. Proton conductivity, IEC, water uptake, dimensional stability were determined using procedure outlined elsewhere. Membrane electrode assembles(MEAs) were prepared using catalyst coated substrate (CCS) method. The active area was 5cm, and catalyst loading was approximately 0.3mg/cm. Single cell performances of surface fluorinated SPSSN membranes were measured under a flow rate of H2/O2=100 sccm/ 100 sccm at 70 C Results and Discussion The effect of surface fluorination of SPSSN membrane on IEC, water uptake, and dimensional stability are listed in Table 1. These membrane properties were improved by exposing them to highly reactive F2 gas diluted in N2 for a short period time. Table 1. Basic PEM properties of surface fluorination membranes
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synthesis of crosslinked Sulfonated Poly phenylene sulfide sulfone nitrile for direct methanol fuel cell applications
Macromolecular Rapid Communications, 2009Co-Authors: Duong Sang Phu, Chang Hyun Lee, Chi Hoon Park, So Young Lee, Young Moo LeeAbstract:With a view towards direct methanol fuel cell applications, novel Sulfonated Poly(phenylene sulfide sulfone nitrile) (sPPSSfN) has been prepared and subsequently crosslinked by a Friedel-Craft reaction using 4,4'-oxybis(benzoic acid) as a crosslinker to achieve lower water swelling and lower methanol permeability. The dimensional change of SPPSSfN40 is 43.7% in 90 °C liquid water but that of the crosslinked membrane, XsPPSSfN40, is 23.3% while maintaining proton conductivity at 0.22 S · cm(-1) . These results show that the Friedel-Craft crosslinking of the novel sPPSSfN membrane effectively reduces water uptake and the degree of swelling while improving the dimensional stability and maintaining high proton conductivity.
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Sulfonated Poly(arylene ether sulfone)-silica nanocomposite membrane for direct methanol fuel cell (DMFC)
Journal of Membrane Science, 2007Co-Authors: Chang Hyun Lee, Young Taik Hong, Kyung A. Min, Ho Bum Park, Byung Ok Jung, Young Moo LeeAbstract:Inorganic nanoparticles in nanocomposite membranes significantly affect the characteristics of those membranes, such as proton and methanol transport behavior, membrane durability, and electrochemical single cell result. Therefore, the inorganic nanoparticles should be deliberately chosen to fabricate composite membranes with desirable properties for DMFC. In this study, Sulfonated Poly(arylene ether sulfone) (SPAES) and hydrophilic fumed silica (SiO2) were used as a Polymer matrix and an inorganic nanoparticle, respectively. The SiO2 nanoparticles have various surface areas (150, 200, 300, and 380 m 2 g −1 ) and average particle sizes (7, 12, and 14 nm). The SiO2 nanoparticles are evenly dispersed in the SPAES matrix by aid of a non-ionic surfactant (Pluronics ® L64). Interestingly, SiO2 particles with a high surface area and small particle size showed the best results: high proton conductivity, long membrane life time under oxidative conditions, good dimensional stability, outstanding single cell performance, and reduced methanol crossover. Moreover, SiO2 content plays an important role in membrane microstructures and membrane properties such as proton conductivity and methanol barrier behavior. An excessive SiO2 content caused a large aggregation of SiO2 particles, leading to the deterioration of mechanical properties in nanocomposite membranes. In the present study, optimal SiO2 content for maximizing the fuel cell performance of current nanocomposite membranes was ca. 2 wt.%. © 2007 Elsevier B.V. All rights reserved.
Michael D Guiver - One of the best experts on this subject based on the ideXlab platform.
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durable Sulfonated Poly arylene sulfide sulfone nitrile s containing naphthalene units for direct methanol fuel cells dmfcs
Macromolecules, 2013Co-Authors: Dong Won Shin, Michael D Guiver, So Young Lee, Na Rae Kang, Kang Hyuck Lee, Young Moo LeeAbstract:Sulfonated Poly(arylene sulfide sulfone nitrile)s (SN) were synthesized to investigate the effects of naphthalene units in the Polymer backbone on membrane properties. The small and planar naphthalene in the main chain reduced interdomain distance, as confirmed by molecular simulations and small-angle X-ray scattering patterns. The SN Polymer membranes exhibited excellent chemical and mechanical properties, better than those of their phenylene counterpart (SP). In particular, the water uptake and swelling ratio of the SN membranes were much lower than those of the SP membranes. Furthermore, the SN membranes exhibited a greatly reduced methanol permeability ((9–17) × 10–8 cm2 s–1) compared to Nafion 212 (330 × 10–8 cm2 s–1) at 30 °C in 10 M methanol. Moreover, sulfide- and naphthalene-based chemical structure of the SN membranes enhanced their DMFC single cell performance and long-term stability during fuel cell operation.
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morphological transformation during cross linking of a highly Sulfonated Poly phenylene sulfide nitrile random coPolymer
Energy and Environmental Science, 2012Co-Authors: So Young Lee, Chang Hyun Lee, Michael D Guiver, Na Rae Kang, Dong Won Shin, Kwansoo Lee, Young Moo LeeAbstract:We present a new approach of morphological transformation for effective proton transport within ionomers, even at partially hydrated states. Highly Sulfonated Poly(phenylene sulfide nitrile) (XESPSN) random network coPolymers were synthesized as alternatives to state-of-the-art perfluorinated Polymers such as Nafion®. A combination of thermal annealing and cross-linking, which was conducted at 250 °C by simple trimerisation of ethynyl groups at the chain termini, results in a morphological transformation. The resulting nanophase separation between the hydrophilic and hydrophobic domains forms well-connected hydrophilic nanochannels for dramatically enhanced proton conduction, even at partially hydrated conditions. For instance, the proton conductivity of XESPSN60 was 160% higher than that of Nafion® 212 at 80 °C and 50% relative humidity. The water uptake and dimensional swelling were also reduced and mechanical properties and oxidative stability were improved after three-dimensional network formation. The fuel cell performance of XESPSN membranes exhibited a significantly higher maximum power density than that of Nafion® 212 under partially hydrated environments.
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blend membranes consisting of Sulfonated Poly ether ether ketone and 1h perimidine tethered Polysulfone for direct methanol fuel cells
Electrochemical and Solid State Letters, 2009Co-Authors: Wei Li, Arumugam Manthiram, Michael D GuiverAbstract:Blend membranes consisting of Sulfonated Poly(ether ether ketone) (SPEEK, an acidic Polymer) and various amounts of 1H-perimidine tethered Polysulfone (a basic Polymer) have been prepared and characterized. The blend membranes show increased proton conductivity and decreased ion-exchange capacity and liquid uptake in water and methanol/water solutions com- pared to plain SPEEK. The blend membranes also exhibit better electrochemical performance and lower methanol crossover in direct methanol fuel cells compared to plain SPEEK and Nafion 115 membranes due to an enhancement in proton conductivity through acid―base interactions and an insertion of the 1H-perimidine groups into the ionic clusters of SPEEK.
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acid base blend membranes based on 2 amino benzimidazole and Sulfonated Poly ether ether ketone for direct methanol fuel cells
Electrochemistry Communications, 2007Co-Authors: Arumugam Manthiram, Michael D GuiverAbstract:Abstract Direct methanol fuel cells (DMFC) are attractive for portable and automobile power needs, but their commercialization is hampered by high methanol permeability and the high cost of the currently used Nafion membrane. We report here a novel, low-cost blend membrane consisting of Polysulfone-2-amide-benzimidazole (a basic Polymer) and Sulfonated Poly(ether ether ketone) (an acidic Polymer), which facilitates proton conduction through acid–base interactions while preserving excellent chemical and mechanical stabilities. The blend membrane exhibits performance in DMFC much higher than that of Nafion 115 and similar to that of Nafion 112, but with a remarkably superior long-term performance than Nafion 112 due to significantly reduced methanol crossover, enhancing the commercialization prospects of DMFC.
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blend membranes based on Sulfonated Poly ether ether ketone and Polysulfone bearing benzimidazole side groups for proton exchange membrane fuel cells
Electrochemistry Communications, 2006Co-Authors: Yongzhu Fu, Arumugam Manthiram, Michael D GuiverAbstract:Abstract A novel acid–base blend membrane based on Sulfonated Poly(ether ether ketone) (SPEEK) and Polysulfone bearing benzimidazole side groups has been synthesized, characterized, and evaluated in proton exchange membrane fuel cell (PEMFC). The benzimidazole group tethered to the Polysulfone backbone acts as a medium through the basic nitrogen for transfer of protons between the sulfonic acid groups of SPEEK, supporting a Grotthuss-type mechanism in addition to the vehicle-type mechanism present among SPEEK. The blend membrane exhibits better performance in PEMFC at 90 and 100 °C compared to the pure SPEEK and Nafion 115 membranes. The Polymers bearing pendant benzimidazole groups offer a promising strategy to develop new membranes that can operate at higher temperatures and low relative humidity.
So Young Lee - One of the best experts on this subject based on the ideXlab platform.
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durable Sulfonated Poly arylene sulfide sulfone nitrile s containing naphthalene units for direct methanol fuel cells dmfcs
Macromolecules, 2013Co-Authors: Dong Won Shin, Michael D Guiver, So Young Lee, Na Rae Kang, Kang Hyuck Lee, Young Moo LeeAbstract:Sulfonated Poly(arylene sulfide sulfone nitrile)s (SN) were synthesized to investigate the effects of naphthalene units in the Polymer backbone on membrane properties. The small and planar naphthalene in the main chain reduced interdomain distance, as confirmed by molecular simulations and small-angle X-ray scattering patterns. The SN Polymer membranes exhibited excellent chemical and mechanical properties, better than those of their phenylene counterpart (SP). In particular, the water uptake and swelling ratio of the SN membranes were much lower than those of the SP membranes. Furthermore, the SN membranes exhibited a greatly reduced methanol permeability ((9–17) × 10–8 cm2 s–1) compared to Nafion 212 (330 × 10–8 cm2 s–1) at 30 °C in 10 M methanol. Moreover, sulfide- and naphthalene-based chemical structure of the SN membranes enhanced their DMFC single cell performance and long-term stability during fuel cell operation.
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morphological transformation during cross linking of a highly Sulfonated Poly phenylene sulfide nitrile random coPolymer
Energy and Environmental Science, 2012Co-Authors: So Young Lee, Chang Hyun Lee, Michael D Guiver, Na Rae Kang, Dong Won Shin, Kwansoo Lee, Young Moo LeeAbstract:We present a new approach of morphological transformation for effective proton transport within ionomers, even at partially hydrated states. Highly Sulfonated Poly(phenylene sulfide nitrile) (XESPSN) random network coPolymers were synthesized as alternatives to state-of-the-art perfluorinated Polymers such as Nafion®. A combination of thermal annealing and cross-linking, which was conducted at 250 °C by simple trimerisation of ethynyl groups at the chain termini, results in a morphological transformation. The resulting nanophase separation between the hydrophilic and hydrophobic domains forms well-connected hydrophilic nanochannels for dramatically enhanced proton conduction, even at partially hydrated conditions. For instance, the proton conductivity of XESPSN60 was 160% higher than that of Nafion® 212 at 80 °C and 50% relative humidity. The water uptake and dimensional swelling were also reduced and mechanical properties and oxidative stability were improved after three-dimensional network formation. The fuel cell performance of XESPSN membranes exhibited a significantly higher maximum power density than that of Nafion® 212 under partially hydrated environments.
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direct surface fluorination of Sulfonated Poly phenylene sulfide sulfone nitrile spssn membrane for high performance fuel cell
Meeting Abstracts, 2010Co-Authors: So Young Lee, Chi Hoon Park, Na Rae Kang, Dong Won Shin, Doo Sung Hwang, Young Moo LeeAbstract:he proton exchange membrane (PEM) is one of the key components in fuel cell systems. The important technical focus is on developing PEMs, which are able to exhibit high proton conductivity, low fuel permeability and reduced water uptake. The perfluoro Sulfonated membranes such as Nafion have been widely used because of its high resistance to chemical attack as well as high proton conductivity in the Polymer backbone. However, they have disadvantages such as low thermal stability due to their low Tg and high reactant permeablility. Up to now, much efforts have been put into the development of novel Sulfonated aromatic hydrocarbon Polymer membranes to overcome drawbacks of Nafion. We have already reported on the novel Sulfonated Poly (phenylene sulfide sulfone nitrile) (SPSSN). The thioether group was introduced to increase the hydrolytic and oxidative stability and excellent thermal stability, even at 120C. Moreover nitrile groups in the backbone were added, which play an important role in reducing water uptake and dimensional swelling without siginificant proton conductivity loss. In this study, we investigate surface modification of Sulfonated Poly(phenylene sulfide sulfone nitrile)(SPSSN) membrane by using direct fluorination. Surface fluorination treatments convert some C-H into C-F bonds on the membrane surface. In particular, the surface enrichment of fluorine atoms led to anisotropic swelling behavior, associated with stable electrode interface formation. Strikingly random coPolymer as a Polymer matrix showed, the low surface free energy of the C-F bonds induced a well difined continuous ionic channel structure, similar to those of multiblock coPolymer. Therefore, surface fluorinated SPSSN membranes were expected to improve proton conductivity, reduce water uptake and increase high dimensional stability compared to pristine membrane due to the synergy effect of -CNgroup. Experimental Sulfonated Poly(phenylene sulfide sulfone nitrile) random Polymer (SPSSN) were synthesized as previously reported. SPSSN membrane with an average thickness of 60 μm was obtained after casting a 15 wt% solution on the glass plate, and drying in a vacuum oven. Then, the membrane was acidified by 1M H2SO4 boiling solution for 4 hours and washed in boiling water for 4 hours. Surface fluorinated SPSSN membranes were prepared by dilute fluorine gas (500 ppm F2/N2 at atmospheric pressure) at 25 C for 10, 30, and 60 minutes in a reaction chamber. The degree of fluorination was same on both sides of the membranes. The successful surface fluorination of SPSSN was confirmed via ESCA. Proton conductivity, IEC, water uptake, dimensional stability were determined using procedure outlined elsewhere. Membrane electrode assembles(MEAs) were prepared using catalyst coated substrate (CCS) method. The active area was 5cm, and catalyst loading was approximately 0.3mg/cm. Single cell performances of surface fluorinated SPSSN membranes were measured under a flow rate of H2/O2=100 sccm/ 100 sccm at 70 C Results and Discussion The effect of surface fluorination of SPSSN membrane on IEC, water uptake, and dimensional stability are listed in Table 1. These membrane properties were improved by exposing them to highly reactive F2 gas diluted in N2 for a short period time. Table 1. Basic PEM properties of surface fluorination membranes
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synthesis of crosslinked Sulfonated Poly phenylene sulfide sulfone nitrile for direct methanol fuel cell applications
Macromolecular Rapid Communications, 2009Co-Authors: Duong Sang Phu, Chang Hyun Lee, Chi Hoon Park, So Young Lee, Young Moo LeeAbstract:With a view towards direct methanol fuel cell applications, novel Sulfonated Poly(phenylene sulfide sulfone nitrile) (sPPSSfN) has been prepared and subsequently crosslinked by a Friedel-Craft reaction using 4,4'-oxybis(benzoic acid) as a crosslinker to achieve lower water swelling and lower methanol permeability. The dimensional change of SPPSSfN40 is 43.7% in 90 °C liquid water but that of the crosslinked membrane, XsPPSSfN40, is 23.3% while maintaining proton conductivity at 0.22 S · cm(-1) . These results show that the Friedel-Craft crosslinking of the novel sPPSSfN membrane effectively reduces water uptake and the degree of swelling while improving the dimensional stability and maintaining high proton conductivity.
Yuezhong Meng - One of the best experts on this subject based on the ideXlab platform.
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synthesis and properties of novel Sulfonated Poly arylene ether sulfone ionomers for vanadium redox flow battery
Energy Conversion and Management, 2010Co-Authors: Dongyang Chen, Shuanjin Wang, Min Xiao, Yuezhong MengAbstract:Novel Sulfonated Poly(arylene ether sulfone)s with electron-withdrawing sulfone groups in each repeat unit were synthesized via step Polymerization followed by post-sulfonation using chlorosulfonic acid. The sulfonation degree can be readily controlled by adjusting the feed ratio of the repeat unit of Polymers to chlorosulfonic acid. The synthesized Polymers are soluble in common aprotic solvents such as dimethyl sulfoxide, N,N′-dimethylacetamide and dimethylformamide, and can be cast into transparent membranes from their solutions. The ion exchange capacity, water uptake, swelling ratio, sulfonation degree, mechanical property, oxidative property, thermal property and proton conductivity were investigated in detail using different methodologies. As an objective to apply these Polymers as separators for vanadium redox flow battery, the VO2+ permeability and cell performance for the single cell were examined and assessed.
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synthesis and characterization of novel Sulfonated Poly arylene thioether ionomers for vanadium redox flow battery applications
Energy and Environmental Science, 2010Co-Authors: Dongyang Chen, Shuanjin Wang, Min Xiao, Yuezhong MengAbstract:High-molecular-weight Poly(arylene thioether ketone) (PTK) and Poly(arylene thioether ketone ketone) (PTKK) Polymers were successfully synthesized by one-pot Polymerization of N,N′-dimethy-S-carbamate masked dithiols with activated dihalo compounds, followed by post-sulfonation using chlorosulfonic acid as the sulfonation agent in dichloromethane solution to give the production of Sulfonated Poly(arylene thioether ketone) (SPTK) and Sulfonated Poly(arylene thioether ketone ketone) (SPTKK) with appropriate ion-exchange capacities. The chemical structures were confirmed by 1H NMR, FT-IR and elemental analysis (EA). The thermal properties were fully investigated by TGA-IR. The synthesized SPTK and SPTKK Polymers are soluble in aprotic solvents such as N,N′-dimethylacetamide (DMAc), N,N′-dimethylformamide and dimethyl sulfoxide, and can be cast into membranes on a glass plate from their DMAc solution. The proton conductivities of these membranes are comparable to Nafion117 membranes under the same conditions. Cell performance tests showed that the vanadium redox flow batteries (VRBs) assembled with SPTK and SPTKK membranes possessed higher Coulombic efficiencies than VRBs assembled with Nafion117 membranes at the current density of 50 mA cm−2, because of their one-order-of magnitude lower VO2+ permeabilities. In conclusion, these ionomers could be promising candidates as proton-exchange membranes for vanadium redox flow battery (VRB) applications.
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preparation and properties of Sulfonated Poly fluorenyl ether ketone membrane for vanadium redox flow battery application
Journal of Power Sources, 2010Co-Authors: Dongyang Chen, Shuanjin Wang, Min Xiao, Yuezhong MengAbstract:Abstract In order to develop novel membranes for vanadium redox flow battery (VRB) with low self-discharge rate and low cost, Sulfonated Poly(fluorenyl ether ketone) (SPFEK) was synthesized directly via aromatic nucleophilic Polycondensation of bisphenol fluorene with 60% Sulfonated difluorobenzophenone and 40% difluorobenzophenone. The SPFEK membrane shows the lower permeability of vanadium ions. The open circuit voltage evaluation demonstrates that the SPFEK membrane is superior to Nafion 117 membrane in self-discharge test. Both energy efficiencies (EE) and power densities of the VRB single cell based on the SPFEK membrane are higher than those of the VRB with Nafion 117 membrane at the same current densities. The highest coulombic efficiency (CE) of VRB with SPFEK membrane is 80.3% while the highest CE of the VRB with Nafion 117 membrane is 77.0%. The SPFEK membrane shows the comparative stability to Nafion 117 membrane in VO 2 + electrolyte. The experimental results suggest that SPFEK membrane is a promising ion exchange membrane for VRB.
Michael A Hickner - One of the best experts on this subject based on the ideXlab platform.
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specific ion effects on the permselectivity of Sulfonated Poly ether sulfone cation exchange membranes
Journal of Membrane Science, 2016Co-Authors: Harrison J Cassady, Emily C Cimino, Manish Kumar, Michael A HicknerAbstract:Abstract Water uptake and permselectivity were measured for five Sulfonated Poly(ether sulfone) cation exchange membranes with varying degrees of functionalization from 20% to 60%. Experiments were conducted in aqueous salt solutions of LiCl, NaCl, KCl, Li2SO4, Na2SO4 and K2SO4 to isolate the effect of counter-ions and co-ions on membrane permselectivity. Water uptake ranged from 0.13 g water / g Polymer to 0.76 g water / g Polymer depending on the degree of functionalization and salt used, but was not found to describe the permselectivity differences between salts as the counter-ion and co-ion were varied. This lack of correlation between water uptake and permselectivity is counter to expectations for swollen Polymers. Counter-ion binding affinity, charge density and dilute solution mobility were identified as factors influencing membrane permselectivity. Specifically, counter-ions with higher binding affinities to the fixed charge group of the Polymer showed lower permselectivities due to counter-ion condensation. Co-ion polarizability was identified as the primary factor for co-ion effects on permselectivity, with more polarizable co-ions resulting in lower membrane permselectivities.
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stable fluorinated Sulfonated Poly arylene ether membranes for vanadium redox flow batteries
RSC Advances, 2012Co-Authors: Dongyang Chen, Soowhan Kim, Gary Yang, Michael A HicknerAbstract:Partially fluorinated Sulfonated Poly(arylene ether) (SFPAE) coPolymers were investigated as chemically stable proton exchange membranes for application in vanadium redox flow batteries (VRFB). The membranes' proton conductivity and vanadium ion permeability were quantified and correlated to other membrane properties such as water uptake and tensile modulus to provide insight into the tradeoffs in the design of new membranes for flow battery applications. The SFPAE-1.8 sample with optimized proton conductivity to vanadium permeability selectivity was selected for evaluation in a VRFB device and compared to the performance of a cell with a NAFION® N212 membrane. The VRFB cell with a SFPAE-1.8 membrane had higher coulombic efficiency, voltage efficiency, and energy efficiency compared to a VRFB with a N212 membrane under all tested current densities. The capacity fade of a VRFB with the SFPAE-1.8 membrane was 1.1 mA h per cycle, which was about 7 times lower than the fade experienced for a VRFB with a N212 membrane. The performance characteristics of the device could be correlated directly to the membrane properties and this work demonstrates our progress towards high-performance, low-cost, long-lifetime ion exchange membranes for electrochemical energy storage devices.
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transport in Sulfonated Poly phenylene s proton conductivity permeability and the state of water
Polymer, 2006Co-Authors: Michael A Hickner, Cy H Fujimoto, Chris J CorneliusAbstract:The transport properties of a series of Sulfonated Poly(phenylene)s were found to strongly correlate to the ion exchange capacity of the Polymer. Sulfonated Poly(phenylene) membranes have shown promise as proton exchange membranes for fuel cells. In general, these materials have minimal methanol and glucose crossover while maintaining high proton conductivity, which is necessary for efficient operation of fuel cells powered by liquid fuels. Proton conductivity in addition to methanol and glucose permeability were compared to Nafion as a function of ion exchange capacity. It was found that the transport in Nafion membranes was much higher than that in the Sulfonated Poly(phenylene)s for a given ion exchange capacity. Water content and its absorbed state within membranes were elucidated by differential scanning calorimetry in order to provide insight as to how the transport properties varied between the materials studied. The domain morphology of these ionomers was imaged with transmission electron microscopy in order to contrast the morphological differences between Nafion and the Sulfonated Poly(phenylene) series.
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processing induced morphological development in hydrated Sulfonated Poly arylene ether sulfone coPolymer membranes
Polymer, 2003Co-Authors: Yu Seung Kim, Michael A Hickner, Limin Dong, Bryan S Pivovar, James E. McgrathAbstract:Abstract The development of morphological solid-state structures in Sulfonated Poly(arylene ether sulfone) coPolymers (acid form) by hydrothermal treatment was investigated by water uptake, dynamic mechanical analysis (DMA), and tapping mode atomic force microscopy (TM-AFM). The water uptake and DMA studies suggested that the materials have three irreversible morphological regimes, whose intervals are controlled by coPolymer composition and hydrothermal treatment temperature. Ambient temperature treatment of the membranes afforded a structure denoted as Regime1 . When the coPolymer membranes were exposed to a higher temperature, AFM revealed a morphology ( Regime2 ) where the phase contrast and domain connectivity of the hydrophilic phase of the coPolymers were greatly increased. A yet higher treatment temperature was defined which yielded a third regime, likely related to viscoelastic relaxations associated with the hydrated glass transition temperature (hydrated T g ). The required temperatures needed to produce transitions from Regime1 to Regime2 or Regime3 decreased with increasing degree of disulfonation. These temperatures correspond to the percolation and hydrogel temperatures, respectively. Poly(arylene ether sulfone) coPolymer membranes with a 40% disulfonation in Regime2 under fully hydrated conditions showed similar proton conductivity (∼0.1 S/cm) to the well-known perfluorinated coPolymer Nafion ® 1135 but exhibited higher modulus and water uptake. The proton conductivity and storage modulus are discussed in terms of each of the morphological regimes and compared with Nafion 1135. The results are of particular interest for either hydrogen or direct methanol fuel cells where conductivity and membrane permeability are critical issues.
