Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl 2 via the Friedel–Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a) crosslinking on the sulfonic acid groups; and (b) crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol) showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO 2+ crossover compared to Nafion.
References
[1]
Hosseiny, S.S.; Saakes, M.; Wessling, M. A polyelectrolyte membrane based vanadium/air redox flow battery. Electrochem. Commun.？2011, 13, 751–754, doi:10.1016/j.elecom.2010.11.025.
[2]
Menictas, C.; Skyllas-Kazacos, M. Performance of vanadium-oxygen redox fuel cell. J. Appl. Electrochem.？2011, 41, 1223–1232, doi:10.1007/s10800-011-0342-8.
[3]
Haneko, H.; Akira, N.K.; Kanji, S.; Masato, N. Redox Battery. Eur. Patent 0517217, 9 December 1997.
[4]
Haneko, H.; Akira, N.; Ken, N.; Kanji, S.; Masato, N. Redox Battery. U.S. Patent 5,318,865, 7 June 1994.
[5]
Li, X.; Zhang, H.; Mai, Z.; Zhang, H.; Vankelecom, I. Ion exchange membranes for vanadium redox flow battery (VRB) applications. Energy Environ. Sci.？2011, 4, 1147–1160, doi:10.1039/c0ee00770f.
[6]
Hosseiny, S.S.; Wessling, M. Advanced Membrane Science and Technology for Sustainable Energy and Environmental Applications; Woodhead Publishing: Cambridge, UK, 2011.
[7]
Jia, C.; Liu, J.; Yan, C. A significantly improved membrane for vanadium redox flow battery. J. Power Sources？2010, 195, 4380–4383, doi:10.1016/j.jpowsour.2010.02.008.
[8]
Kreuer, K.D. On the development of proton conducting polymer membranes for hydrogen and methanol fuel cells. J. Membr. Sci.？2001, 185, 29–39, doi:10.1016/S0376-7388(00)00632-3.
[9]
Luo, Q.; Zhang, H.; Chen, J.; You, D.; Sun, C.; Zhang, Y. Preparation and characterization of Nafion/SPEEK layered composite membrane and its application in vanadium redox flow battery. J. Membr. Sci.？2008, 325, 553–558, doi:10.1016/j.memsci.2008.08.025.
[10]
Daoust, D.; Devaux, J.; Godard, P. Part 3. General kinetic model of the sulfonation of PEEK fluoroarylketone chain-end repeat unit. Polym. Int.？2001, 50, 932–936, doi:10.1002/pi.719.
[11]
Shibuyal, N.; Porter, R.S. Kinetics of PEEK sulfonation in concentrated sulfuric acid. Macromolecules？1992, 25, 6495–6499, doi:10.1021/ma00050a017.
[12]
Zeng, J.; Jiang, C.; Wang, Y.; Chen, J.; Zhu, S.; Zhao, B.; Wang, R. Studies on polypyrrole modified nafion membrane for vanadium redox flow battery. Electrochem. Commun.？2008, 10, 372–375, doi:10.1016/j.elecom.2007.12.025.
[13]
Luu, D.X.; Kim, D. Strontium cross–linked sPEEK proton exchange membranes for fuel cell. Solid State Ionics？2011, 192, 627–631, doi:10.1016/j.ssi.2010.05.007.
[14]
Xuea, Y.; Fub, R.; Wub, C.; Leeb, J.Y. Acid–base hybrid polymer electrolyte membranes based on SPEEK. J. Membr. Sci.？2010, 350, 148–153, doi:10.1016/j.memsci.2009.12.022.
[15]
Kerres, J.; Ullrich, A.; Meier, F.; H？ring, T. Synthesis and characterization of novel acid–base polymer blends for application in membrane fuel cells. Solid State Ionics？1999, 125, 243–249, doi:10.1016/S0167-2738(99)00181-2.
[16]
Chen, J.; Maekawaa, Y.; Asanoa, M.; Yoshidaa, M. Double crosslinked polyetheretherketone-based polymer electrolyte membranes prepared by radiation and thermal crosslinking techniques. Polymer？2007, 48, 6002–6009, doi:10.1016/j.polymer.2007.08.005.
[17]
Vona, M.L.D.; Sgreccia, E.; Licoccia, S.; Alberti, G.; Torte, L.; Knauth, P. Analysis of temperature-promoted and solvent-assisted cross-linking in sulfonated Poly(ether ether ketone) (SPEEK) proton-conducting membranes. J. Phys. Chem.？2009, 113, 7505–7512, doi:10.1021/jp9006679.
Yao, H.; Zhu, J.; McKinney, M.A.; Wilkie, C.A. Cross-Linking of polystyrene by friedel-crafts chemistry: Multifunctional additives. J. Vinyl Addit. Technol.？2000, 6, 205–210, doi:10.1002/vnl.10254.
[25]
Compan, V.; Riande, E.; Fernandez-Carretero, F.; Berezina, N.; Sytcheva, A.R. Influence of polyaniline intercalations on the conductivity and permselectivity of perfluorinated cation-exchange membranes. J. Membr. Sci.？2008, 318, 255–263, doi:10.1016/j.memsci.2008.02.048.
[26]
Mohammadi, T.; Skyllas-Kazacos, M. Preparation of sulfonated composite membrane for vanadium redox flow battery applications. J. Membr. Sci.？1995, 107, 35–45, doi:10.1016/0376-7388(95)00096-U.
[27]
Luo, X.; Lu, Z.; Xi, J.; Wu, Z.; Zhu, W.; Chen, L.; Qiu, X. Influences of permeation of vanadium ions through PVDF-g-PSSA membranes on performances of vanadium redox flow batteries. J. Phys. Chem. B？2005, 109, 20310–20314, doi:10.1021/jp054092w. 16853627
[28]
Sun, C.; Chen, J.; Zhang, H.; Han, X.; Luo, Q. Investigations on transfer of water and vanadium ions across Nafion membrane in an operating vanadium redox flow battery. J. Power Sources？2010, 195, 890–897, doi:10.1016/j.jpowsour.2009.08.041.
[29]
Deb, P.C.; Rajput, L.D.; Hande, V.R.; Sasane, S.; Kumar, A. Modification of sulfonated poly(ether ether ketone) with phenolic resin. Polym. Adv. Technol.？2007, 18, 419–426, doi:10.1002/pat.830.
[30]
Stejkal, E.; Tanner, J. Spin diffusion measurements: Spin echoes in the presence of a time-dependent field gradient. J. Chem. Phys.？1965, 42, 288–292, doi:10.1063/1.1695690.
[31]
Murray, K.A.; Holmes, A.B.; Moratti, S.C.; Rumbles, G. Conformational changes in regioregular polythiophenes due to crosslinking. J. Mater. Chem.？1999, 9, 2109–2116, doi:10.1039/a902683e.
[32]
Masamitsu, S.; Satoshi, M.; Haruyuki, O.; Masahiro, T. Photo-cross-linkable polymers with thermally degradable property. Chem. Mater.？2002, 14, 334–340, doi:10.1021/cm0103646.
[33]
Okamura, H.; Takatori, Y.; Tsunooka, M.; Shirai, M. Synthesis of random and block copolymers of styrene and styrenesulfonic acid with low polydispersity using nitroxide-mediated living radical polymerization technique. Polymer？2002, 43, 3155–3162, doi:10.1016/S0032-3861(02)00162-3.
[34]
Li, J.; Wilmsmeyer, K.G.; Madsen, L.A. Anisotropic diffusion and morphology in perfluorosulfonate ionomers investigated by NMR. Macromolecules？2008, 42, 255–262.
[35]
Filipoi, C.; Demco, D.E.; Zhu, X.; Vinokur, R.; Conradi, O.; Fechete, R.; M？ller, M. Channel orientation anisotropy in perfluorosulfonic acid/SiO2 composite proton exchange membranes: Water self-diffusion study using NMR. Chem. Phys. Lett.？2011, 513, 251–255, doi:10.1016/j.cplett.2011.08.006.
[36]
Xi, J.; Wu, Z.; Qiu, X.; Chen, L. Nafion/SiO2 hybrid membrane for vanadium redox flow battery. J. Power Sources？2007, 166, 531–536, doi:10.1016/j.jpowsour.2007.01.069.
