Highly Proton-Conducting Membranes Based on Poly(arylene ether)s with Densely Sulfonated and Partially Fluorinated Multiphenyl for Fuel Cell Applications (original) (raw)
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Multiblock sulfonated-fluorinated poly (arylene ether) s for a proton exchange membrane fuel cell
Polymer, 2006
New proton exchange membranes were prepared and evaluated as polymer electrolytes for a proton exchange membrane fuel cell (PEMFC). Sulfonated-fluorinated poly(arylene ether) multiblocks (MBs) were synthesized by nucleophilic aromatic substitution of highly activated fluorine terminated telechelics made from decafluorobiphenyl with 4,4 0-(hexafluoroisopropylidene)diphenol and hydroxyl-terminated telechelics made from 4,4 0-biphenol and 3,3 0-disulfonated-4,4 0-dichlorodiphenylsulfone. Membranes with various sulfonation levels were successfully cast from N-methyl-2-pyrrolidinone. An increase sulfonated block size in the copolymer resulted in enhanced membrane ion exchange capacity and proton conductivity. The morphological structure of MB copolymers was investigated by tapping mode atomic force microscopy (TM-AFM) and compared with those of Nafion w and sulfonated poly(arylene ether) random copolymers. AFM images of MBs revealed a very well defined phase separation, which may explain their higher proton conductivities compared to the random copolymers. The results are of particular interest for hydrogen/air fuel cells where conductivity at high temperature and low relative humidity is a critical issue.
Polysulfone ionomers for proton-conducting fuel cell membranes
Electrochimica Acta, 2005
Polysulfones and polyphenylsulfones having pendant phenyl groups with sulfonic acid units have been prepared by lithiation of the respective polymer, followed by reaction with 2-sulfobenzoic acid cyclic anhydride. The resulting ionomers were cast into membranes and properties such as thermal stability, ion-exchange capacity, water sorption and proton conductivity were evaluated. These membranes proved to have a high thermal stability, with a decomposition temperature between 300 and 350 • C, and a high proton conductivity, 60 mS/cm at 70 • C for a polyphenylsulfone with 0.9 sulfonic acid group per repeating unit measured at 100% relative humidity. Moreover, some of the membranes endured immersion in water at temperatures ranging from 20 to 150 • C without swelling extensively, and therefore kept their mechanical stability under these conditions. It was also shown that these membranes retained a high conductivity up to 150 • C under humidifying conditions. The combination of properties make these membranes potential candidates for fuel cells operating at temperatures above 100 • C.
Journal of Polymer Science Part B: Polymer Physics, 2017
The synthesis and characterization of new di-and tetra-sulfonated ether diketone monomers are described. From these monomers, a wide series of sulfonated poly(arylene ether ketone)s (SPAEK) are synthesized by varying the sulfonic acid repartition along the polymer backbones. Their chemical structures are thoroughly characterized by NMR. From these polymers tough membranes are obtained from solution casting method and their water uptake, ionic conductivity, and water/ gas permeation properties are determined and compared with those of Nafion membrane. Preliminary fuel cell tests show that SPAEK membranes are promising candidates for fuel cell application. This work brings new insights concerning the beneficial effects of introducing densely sulfonated monomers in a polyarylether macromolecular structure along with fluorinated groups improving conductivity while reducing unwanted excessive swelling. V
Proton-conducting membranes from poly(ether sulfone)s grafted with sulfoalkylamine
Journal of Membrane Science, 2013
Highly sulfonated poly(ether sulfone)s with densely populated flexible acid side chains were prepared for fuel cell applications by polycondensation of 3,3'-dihydroxybenzidine with bis(4-fluorophenyl)sulfone and 4,4 0 -biphenol, followed by postsulfonation using 1,4-butanesultone at room temperature. The sulfonated polymers gave tough, flexible, and transparent membranes by solvent casting. The membranes had high ion exchange capacity (IEC) values (2.47-2.95 mequiv/g) and displayed good proton conductivities in the range of 13.90-20.90 Â 10 À 2 and 1.08-2.21 Â 10 À 2 S/cm at 95% and 35% relative humidity (RH) (80 1C), respectively. In particular, the S-PES-55 membrane with the highest IEC value showed higher or comparable proton conductivity than that of Nafion 212 in the range of 35-95% RH. The morphologies of these membranes were investigated by TEM analysis, which exhibited wellconnected hydrophilic channels due to their high IEC values and densely populated flexible acid side chains. In contrast with many reported highly sulfonated polymers, the membranes showed good dimensional stability regardless of their high IEC values.
Membranes
In this study, a series of high molecular weight ionomers of hexaarylbenzene- and fluorene-based poly(arylene ether)s were synthesized conveniently through condensation and post-sulfonation modification. The use a of blending method might increase the stacking density of chains and affect the formation both of interchain and intrachain proton transfer clusters. Multiscale phase separation caused by the dissolution and compatibility differences of blend ionomer in high-boiling-point solvents was examined through analysis and simulations. The blend membranes produced in this study exhibited a high proton conductivity of 206.4 mS cm−1 at 80 °C (increased from 182.6 mS cm−1 for precursor membranes), excellent thermal resistance (decomposition temperature > 200 °C), and suitable mechanical properties with a tensile strength of 73.8–77.4 MPa. As a proton exchange membrane for fuel cell applications, it exhibits an excellent power efficiency of approximately 1.3 W cm−2. Thus, the ionome...
Journal of Power Sources, 2007
In the present study, we examine the water and proton transport properties of hexafluorinated sulfonated poly(arylenethioethersulfone) (6F-SPTES) copolymer membranes for applications to proton exchange membrane fuel cells (PEMFCs). The 6F-SPTES copolymer membranes build upon the structures of previously studied sulfonated poly(arylenethioethersulfone) (SPTES) copolymer membranes to include CF 3 functional groups in efforts to strengthen water retention and extend membrane performance at elevated temperatures (above 120 • C). The 6F-SPTES copolymer membranes sustain higher water self-diffusion and greater proton conductivities than the commercial Nafion ® membrane. Water diffusion studies of the 6F-SPTES copolymer membranes using the pulsed-field gradient spin-echo NMR technique reveal, however, the fluorinated membranes to be somewhat unfavorable over their non-fluorinated counterparts as high temperature membranes. In addition, proton conductivity measurements of the fluorinated membranes up to 85 • C show comparable results with the non-fluorinated SPTES membranes.
Journal of Polymer Science Part A: Polymer Chemistry, 2011
Three series of fully aromatic ionomers with naphthalene moieties and pendant sulfobenzoyl side chains were prepared via K 2 CO 3 mediated nucleophilic aromatic substitution reactions. The first series consisted of poly(arylene ether)s prepared by polycondensations of 2,6-difluoro-2 0 -sulfobenzophenone (DFSBP) and 2,6-dihydroxynaphthalene or 2,7-dihydroxynaphthalene (2,7-DHN). In the second series, copoly-(arylene ether nitrile)s with different ion-exchange capacities (IECs) were prepared by polycondensations of DFSBP, 2,6difluorobenzonitrile (DFBN), and 2,7-DHN. In the third series, bis(4-fluorophenyl)sulfone was used instead of DFBN to prepare copoly(arylene ether sulfone)s. Thus, all the ionomers had sulfonic acid units placed in stable positions close to the electron withdrawing ketone link of the side chains. Mechanically strong proton-exchange membranes with IECs between 1.1 and 2.3 meq g À1 were cast from dimethylsulfoxide solutions. High thermal stability was indicted by high degradation temperatures between 266 and 287 C (1 C min À1 under air) and high glass transition temperatures between 245 and 306 C, depending on the IEC. The copolymer membranes reached proton conductivities of 0.3 S cm À1 under fully humidified conditions. At IECs above $1.6 meq g À1 , the copolymer membranes reached higher proton conductivities than Nafion V R in the range between À20 and 120 C. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 734-745, 2011
2011
which is two times longer than that of un-fluorinated SPFEK. The PEM properties and single fuel cell performances were investigated by comparison of un-and fluorinated polymer ionomers. The fluorinated membranes demonstrated an enhanced hydrophobic surface property, increased proton conductivities and better single fuel cell performances. Surface fluorination provides a convenient and useful approach to prepare highly proton conductive membrane with long life-time PEM fuel cell applications.
On the development of proton conducting polymer membranes for hydrogen and methanol fuel cells
Journal of Membrane Science, 2001
The transport properties and the swelling behaviour of NAFION and different sulfonated polyetherketones are explained in terms of distinct differences on the microstructures and in the pK a of the acidic functional groups. The less pronounced hydrophobic/hydrophilic separation of sulfonated polyetherketones compared to NAFION corresponds to narrower, less connected hydrophilic channels and to larger separations between less acidic sulfonic acid functional groups. At high water contents, this is shown to significantly reduce electroosmotic drag and water permeation whilst maintaining high proton conductivity. Blending of sulfonated polyetherketones with other polyaryls even further reduces the solvent permeation (a factor of 20 compared to NAFION), increases the membrane flexibility in the dry state and leads to an improved swelling behaviour. Therefore, polymers based on sulfonated polyetherketones are not only interesting low-cost alternative membrane material for hydrogen fuel cell applications, they may also help to reduce the problems associated with high water drag and high methanol cross-over in direct liquid methanol fuel cells (DMFC). The relatively high conductivities observed for oligomers containing imidazole as functional groups may be exploited in fully polymeric proton conducting systems with no volatile proton solvent operating at temperatures significantly beyond 100 • C, where methanol vapour may be used as a fuel in DMFCs.