Alpay ŞAHİN, Muzaffer BALBAŞI, İrfan AR, Handan AKTAN

Silika destekli, fosforlanmış poli(vinil alkol) bazlı membranların sentezlenmesi ve karakterizasyonu

Polimer elektrolit membranlı yakıt hücreleri (PEMYH), yüksek verimliliğe sahip, güvenilir ve çevre dostusistemler olmaları nedeniyle, son yıllarda araçlar ve diğer taşınabilir uygulamalar için en çok gelecek vaat edenalternatif enerji kaynağı adayıdır. PEMYH’ nin en önemli kısmı, anottan katota proton taşınımını sağlayan veyakıt ile oksitleyici gazların temasını engellemek için bariyer görevi yapan polimer elektrolit membranlardır.Nafion® gibi perflorosülfonik asit bazlı polimer membranlar, sahip oldukları kimyasal, mekanik özellikler veyüksek proton iletkenlikleri nedeniyle PEMYH’ inde elektrolit olarak sıklıkla kullanılmaktadırlar. Ancak Nafion®membranların yüksek sıcaklıklarda proton iletkenliklerinin düşmesi ve pahalı olmaları nedeniyle alternatifmembran malzemeleri geliştirmeye yönelik yoğun çalışmalar yapılmaktadır. Bu çalışmanın amacı; polimerelektrolit membranlı yakıt hücrelerinde kullanılmak üzere, Nafion® membranlara göre daha iyi özelliklere sahipve ucuz, polivinil alkol (PVA) bazlı kompozit polimerik membran geliştirilmesidir. Membranların fosfonasyonişlemleri Hipofosforöz asit ($H _3PO _2$) kullanılarak yapılmıştır. Daha sonra farklı oranlarda yapıya tetraetil ortosilikat(TEOS) eklenerek membranlar sentezlenmiştir. Bu şekilde hem fosfonasyon derecesinin hem de katkı maddesininmembran özelliklerine etkisi incelenmiştir. Sentezlenen membranlar, Fourier Dönüşüm Kızılötesi Spektroskopisi(FT-IR) , su tutma kapasiteleri, şişme özellikleri, iyon değişim kapasiteleri ve iletkenlik ölçümleri ile karakterizeedilmişlerdir. Membranların su tutma yüzdeleri katkı miktarlarına bağlı olarak şişme özelliği göstermeden %20- 140, iyon değişim kapasiteleri 1,35 – 2,86 meq/g, proton iletkenlikleri ise oda sıcaklığında ve %100 nemlilikte0,56 – 3,43 mS/cm aralığında değişmiştir. Sonuç olarak, yakıt hücreleri için bu çalışmada geliştirilen membranlar,günümüzde en çok kullanılan ve pahalı olan perflorlu membranlara alternatif olması açısından ümit vermiştir.

Synthesis and characterization of phosphonated poly(vinyl alcohol) based membrane with silica support

Polymer electrolyte membrane fuel cells (PEMFC) are considered to be the promising alternative energy sourcefor vehicles and other portable applications due to their high efficiency, confidence and being an environmentallyfriendly technology. The most important part of PEMFC is polymer electrolyte membrane that serves as carrier forthe transportation of protons from anode to cathode and acts as a barrier to avoid the contact between the fuel andoxidant. The perfluorosulfonic acid polymer membranes such as Nafion®, are used as the electrolytes in PEMFCbecause of their favorable chemical features and high proton conductivity. However, because of loss of protonconductivity of Nafion® membranes at high temperatures and their high cost causes to large number of studieshave been devoted to develop alternative membrane materials. The aim of this study is to develop poly(vinylalcohol) (PVA) based composite membranes for fuel cells that has better properties and cheaper than the Nafion®membrane. PVA based membranes with different molar ratios were prepared to understand the effect of theirhypophosphorous acid ($H _3PO _2$) and tetraethyl orthosilicate (TEOS) contents on the conductivity of themembranes. Membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), water uptakecapacity, swelling ratios, ion exchange capacity and conductivity measurements. Water uptake percentages ofmembranes without swelling were found as changing in the range of %20-140 depending on their doped materialcontent. Ion exchange capacities of membranes change in the range of 1.35 – 2.86 meq/g and their protonconductivities at room temperature and 100% RH take place in the range of 0.56 – 3.43 mS/cm. Thesemembranes which were developed in this study for fuel cells, are promising alternative for expensive commercialperflorunated membranes.

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1. Smitha,B., Sridhar, s., Khan, A.A., “Solid polymer electrolyte membranes for fuel cell applications-a review” Journal of Membrane Science, 259 : 10-26 (2005).
2. Ma, X., Zhang, C., Xiao, G., Yan, D., “Synthesis and properties of sulfonated poly(arylene ether phosphine oxide)s for proton exchange membranes”, Journal of Power Sources, 188 : 57–63 (2009).
3. Colicchio, I., Wen, F., Keul, H., Simon, U., Moeller, M., “Sulfonated poly(ether ether ketone)–silica membranes doped with phosphotungstic acid. Morphology and proton conductivity”, Journal of Membrane Science, 326 : 45–57 (2009).
4. Chuang, S., Hsu, S.L., Liu, Y., “Synthesis and properties of fluorine-containing polibenzimidazole/silica nanocomposite membranes for proton exchange membrane fuel cells”, Journal of Membrane Science, 305 : 353-363 (2007).
5. Şahin, A., Balbaşı, M., Ar, İ., “Borik asit ve boron fosfat destekli, sülfolanmış polistiren/polivinil alkol kompozit membran sentezi ve karakterizasyonu”, Gazi Üniversitesi Mühendislik-Mimarlık Fakültesi Dergisi, 24: 137-145 (2009).
6. Alberti, G., Casciola, M., Capitani, D., Donnadio, A., Narducci, R., Pica, M., Sganappa, M., “ Novel Nafion- zirconium phosphate nanocomposite membranes with enhanced stability of proton conductivity at medium temperature and high relative humidity”, Electrochimica Acta, 52 : 8125-8132 (2007).
7. Mehta, V., Cooper, J. S., “Rewiev and analysis of PEM fuel cell design and manufacturing”, Journal of Power Sources, 114 : 32-53 (2002).
8. Wang, G., Weng, Y., Chu, D., Xie D., Chen, R., “Preparation of alkaline anion exchange membranes based on functional poly(ether-imide) polymers for potential fuel cell applications”, Journal of Membrane Science, 326 : 4–8 (2009).
9. Anis, A., Banthia, A. K., Bandyopadhyay, S., “ Synthesis and characterization of polyvinyl alcohol copolymer/phosphomolybdic acid-based crosslinked composite polymer electrolyte membranes”, Journal of Power Sources, 179 : 69-80 (2007)
10. Higa, M., Sugita, M., Maesowa, S., Endo, N., “ Poly(vinyl alcohol)-based polymer electrolyte membranes for direct methanol fuel cell”, Electrochimica Acta (2009)
11. Kumar, G. G., Uthirakumar, P., Nahm, K. S., Elizabeth, R. N., “Fabrication and electro chemical properties of poly vinyl alcohol/para toluene sulfonic acid membranes for the application of DMFC”, Solid State Ionics, 180 : 282-287 (2009).
12. Kim, S. K., Park, H.B., Rhim, J.W. And Lee, Y.M., “Preparation and characterization of crosslinked PVA/SiO2 hybrid membranes containing sulfonic acid groups for direct methanol fuel cell applications”, Journal of Membrane Science, 240: 37-48 (2004).
13. Hirankumar, G., Selvasekarapandian, S.i Kuwata, N., Kawamura, J., Hattori, T., “Thermal; electrical and optical studies on the poly(vinyl alcohol) based polimer electrolytes”, Journal of Power Sources, 144:262-267(2005).
14. Li, L., Wang, Q., Wang, R., “Enchancing mechanical properties of poly(vinyl alcohol) blown films by drawing and surface crosslinking, Journal of Applied Polymer Science”, 98: 774- 779(2005).
15. Kim, D. S., Guiver, M. D., Nam, S. Y., Yun, T. I., Seo, M. Y., Kim, S, J., Hwang, H. S., Rhim, J. W., “Prepertion of ion exchange membranes for fuel cell based on crosslinked poly(vinyl alcohol)with poly(styrene sulfonic acid-co-maleik acid), Journal of Membrane Science, 281:156- 162(2006).
16. Deluca, N.W. And Elabd, Y.A., “Nafion/poly(vinyl alcohol) blends: Effect of composition and annealing temperature on transport properties”, Journal of Membrane Science, 282 : 217-224 (2006).
17. Gohil, J.M., Ray, B., Ray, P., “Studies on the cross-linking of poly(vinyl alcohol)”, Journal of Polymer Research, 13 : 161-169 (2006).
18. Son, J.H., Kang, Y.S. And Won, J., “Poly(vinyl alcohol) -based polymer electrolyte membranes containing polyrotaxane”, Journal of Membrane Science, 281 (1-2): 345-350 (2006).
19. Lin, C.W., Huang, Y.F. And Kanan, A.M., “Semi-interpenetrating network based on cross- linked poly(vinyl alcohol) and poly(styrene sulfonic acid-co-maleic anhydride) as proton exchange fuel cell membranes”, Journal of Power Sources, 164 (2): 449-456 (2007).
20. Yang, C. C., “Synthesis and characterization of cross-linked PVA/TiO2 composite polymer membrane for alkaline DMFC”, Journal of Membrane Science, 2888: 51-60 (2007)
21. T. Yang, “Composite membrane of sulfonated poly(ether ether ketone) and sulfated poly (vinyl alcohol) for use in direct methanol fuel cells, Journal of Membrane Science, (2008).
22. Zhang, Y., Cui, Z., Liu, C., Xing, W., Zhang, J., “Implantation of Nafion® ionomer into polyvinyl alcohol/chitosan composites to form novel protonconducting membranes for direct methanol fuel cells”, Journal of Power Sources, (2008).
23. Yang, C. C., Lee, Y. J., Yang, J. M., “Direct methanol fuel cell (DMFC) based on PVA/MMT composite polymer membranes”, Journal of Power Sources, 188 : 30–37 (2009).
24. Huang, Y.F., Chuang, L.C., Kannan, A.M., Lin, C.W., “Proton-conducting membranes with high selectivity from cross-linked poly(vinyl alcohol) and poly(vinyl pyrrolidone) for direct methanol fuel cell applications”, Journal of Power Sources, 186 : 22–28 (2009).
25. Kim, D. S., Park, I. C., Cho, H. I., Kim, D. H., Moon, G. Y., Lee, H. K., Rhim, J. W., “Effect of organo clay content on proton conductivity and methanol transport through crosslinked PVA hybrid membrane for direct methanol fuel cell”, Journal of Industrial and Engineering Chemistry, 15 : 265 (2009).
26. Bhat, S.D., Sahu, A.K., George, C., Pitchumani, S., Sridhar, P., Chandrakumar, N., Singh, K.K., Krishna, N., Shukla, A. K., “Mordenite- incorporated PVA–PSSA membranes as electrolytes for DMFCs”, Journal of Membrane Science, 340 : 73–83 (2009).
27. Kim, D. S., Cho, H. I., Kim, D. H., Lee, B. S.,Lee, B. S., Yoon, S., Kim, Y. S., Moon, G. Y., Byun, H., Rhim, J., “Surface fluorinated poly(vinyl alcohol)/ poly(styrene sulfonic acid- co-maleic acid) membrane for polymer electrolyte membrane fuel cells”, Journal of Membrane Science, (2009).
28. Krishnan, P., Park, J. S. And Kim, C.S., “Preparation of proton-conducting sulfonated poly(ether ether ketone)/boron phosphate composite membranes by an in situ sol–gel process” , Journal of Membrane Science, 279 (1-2): 220-229 (2006).
29. Lavorgna, M., Mascia, L., Mensitieri, G., Gilbert, M., Scherillo, G. And Palomba, B., “Hybridization of nafion membranes by the infusion of functionalized siloxane precursors”, Journal of Membrane Science, 294 (1-2): 159- 168 (2007).
30. Kim, Y.T., Kim, K.H., Song, M.K. And Rhee, H.W., “Nafion/ZrSPP composite membrane for high temperature operation of proton exchange membrane fuel cells”, Current Applied Physics, 6 (4): 612-615 (2006).