Resumé
The electrolyte of choice for low temperature polymer electrolyte fuel cells (PEFCs) has traditionally been DuPontTM Nafion® membranes or similar poly(perfluorosulfonic acid)s. The chemical structure and morphology in the hydrated state of Nafion® is shown in figure 1 from which it is seen that the material consists of hydrophilic and hydrophobic domains. This structure gives hydrated Nafion® very high proton conductivity as well as great stability.[i]
However, the poly(perfluorosulfonic acid) membranes are very expensive materials, and their high water uptake, significant methanol crossover, and relatively poor thermal stability constitute serious drawbacks with respect to their fuel cell use.[ii],[iii],[iv] These aspects propel the search for cheaper and better alternatives.
In this study membrane systems consisting of a hydrophobic poly(ethylene-alt-tetrafluoroethylene) (ETFE) backbone grafted by hydrophilic poly(styrene sulfonic acid) (PSSA) have been synthesized in a three-step procedure comprising electron beam irradiation, grafting polymerization reaction, and sulfonation. The chemical structure of the resulting ETFE-g-PSSA is shown in figure 2, and it is believed that the morphology upon hydration resembles that of the poly(perfluorosulfonic acid)s. The stability of the material has been improved by crosslinking by divinylbenzene (DVB) and by inferring methyl- and tert-butyl substituents on the styrene aromatic ring.
It has been found that crosslinking by divinylbenzene clearly improves the chemical stability of both sulfonated styrene- and methylstyrene/t-butylstyrene-grafted ETFE membranes. However, the crosslinking reduces the proton conductivity due to decreased water uptake, thus downgrading the membranes' electrolytic properties. Grafting with a fraction of DVB in the order of 1-2 vol-% of the total monomers seems to be advantageous for both of the two grafting systems as a compromise between high chemical stability and good proton conductivity of the final membrane. The use of methylstyrene and t-butylstyrene as grafting monomers instead of styrene gives the resulting membranes a significantly increased chemical stability, while a reasonable proton conductivity can still be obtained. Both membrane systems show a smaller methanol uptake than water uptake.
[i] Kreuer, K.-D.; Paddison, S. J.; Spohr, E.; Schuster, M.; Chemical Reviews 104 (2004) 4637-4678
[ii] Skou, E.; Kauranen, P.; Hentschel, J.; Solid State Ionics 97 (1997) 333-337
[iii] Fuel Cell Handbook; Seventh Edition; EG&G Technical Services, Inc.; 2004; p. 3.1-3.25
[iv] Doyle, M.; Rajendran, G. in Handbook of Fuel Cells - Fundamentals, Technology, and Applications, Volume 3: Fuel Cell Technology and Applications: Part 1 (edited by Vielstich, W.; Lamm, A.; Gasteiger, H. A.); John Wiley & Sons Ltd; Chichester; 2003; p. 351-395
| Originalsprog | Engelsk |
|---|---|
| Publikationsdato | 2007 |
| Antal sider | 1 |
| Status | Udgivet - 2007 |
| Begivenhed | Annual meeting of the Danish Electrochemical Society 2007 - Århus, Danmark Varighed: 4. okt. 2007 → 5. okt. 2007 |
Konference
| Konference | Annual meeting of the Danish Electrochemical Society 2007 |
|---|---|
| Land | Danmark |
| By | Århus |
| Periode | 04/10/2007 → 05/10/2007 |
Fingeraftryk
Emneord
- Brændselscelle, membran, polymerelektrolyt, podning, tværbinding, alkylsubstitution, fluorpolymer, ETFE, styren, divinylbenzen, DVB, methylstyren, tert-butylstyren, t-butylstyren
Citer dette
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Preparation and investigation of cheap polymer electrolyte membranes for fuel cells. / Larsen, Mikkel Juul; Ma, Yue; Lund, Peter Brilner; Skou, Eivind Morten.
2007. Poster session præsenteret på Annual meeting of the Danish Electrochemical Society 2007, Århus, Danmark.Publikation: Konferencebidrag uden forlag/tidsskrift › Poster › Forskning
TY - CONF
T1 - Preparation and investigation of cheap polymer electrolyte membranes for fuel cells
AU - Larsen, Mikkel Juul
AU - Ma, Yue
AU - Lund, Peter Brilner
AU - Skou, Eivind Morten
PY - 2007
Y1 - 2007
N2 - The electrolyte of choice for low temperature polymer electrolyte fuel cells (PEFCs) has traditionally been DuPontTM Nafion® membranes or similar poly(perfluorosulfonic acid)s. The chemical structure and morphology in the hydrated state of Nafion® is shown in figure 1 from which it is seen that the material consists of hydrophilic and hydrophobic domains. This structure gives hydrated Nafion® very high proton conductivity as well as great stability.[i] However, the poly(perfluorosulfonic acid) membranes are very expensive materials, and their high water uptake, significant methanol crossover, and relatively poor thermal stability constitute serious drawbacks with respect to their fuel cell use.[ii],[iii],[iv] These aspects propel the search for cheaper and better alternatives. In this study membrane systems consisting of a hydrophobic poly(ethylene-alt-tetrafluoroethylene) (ETFE) backbone grafted by hydrophilic poly(styrene sulfonic acid) (PSSA) have been synthesized in a three-step procedure comprising electron beam irradiation, grafting polymerization reaction, and sulfonation. The chemical structure of the resulting ETFE-g-PSSA is shown in figure 2, and it is believed that the morphology upon hydration resembles that of the poly(perfluorosulfonic acid)s. The stability of the material has been improved by crosslinking by divinylbenzene (DVB) and by inferring methyl- and tert-butyl substituents on the styrene aromatic ring. It has been found that crosslinking by divinylbenzene clearly improves the chemical stability of both sulfonated styrene- and methylstyrene/t-butylstyrene-grafted ETFE membranes. However, the crosslinking reduces the proton conductivity due to decreased water uptake, thus downgrading the membranes' electrolytic properties. Grafting with a fraction of DVB in the order of 1-2 vol-% of the total monomers seems to be advantageous for both of the two grafting systems as a compromise between high chemical stability and good proton conductivity of the final membrane. The use of methylstyrene and t-butylstyrene as grafting monomers instead of styrene gives the resulting membranes a significantly increased chemical stability, while a reasonable proton conductivity can still be obtained. Both membrane systems show a smaller methanol uptake than water uptake.[i] Kreuer, K.-D.; Paddison, S. J.; Spohr, E.; Schuster, M.; Chemical Reviews 104 (2004) 4637-4678[ii] Skou, E.; Kauranen, P.; Hentschel, J.; Solid State Ionics 97 (1997) 333-337[iii] Fuel Cell Handbook; Seventh Edition; EG&G Technical Services, Inc.; 2004; p. 3.1-3.25[iv] Doyle, M.; Rajendran, G. in Handbook of Fuel Cells - Fundamentals, Technology, and Applications, Volume 3: Fuel Cell Technology and Applications: Part 1 (edited by Vielstich, W.; Lamm, A.; Gasteiger, H. A.); John Wiley & Sons Ltd; Chichester; 2003; p. 351-395
AB - The electrolyte of choice for low temperature polymer electrolyte fuel cells (PEFCs) has traditionally been DuPontTM Nafion® membranes or similar poly(perfluorosulfonic acid)s. The chemical structure and morphology in the hydrated state of Nafion® is shown in figure 1 from which it is seen that the material consists of hydrophilic and hydrophobic domains. This structure gives hydrated Nafion® very high proton conductivity as well as great stability.[i] However, the poly(perfluorosulfonic acid) membranes are very expensive materials, and their high water uptake, significant methanol crossover, and relatively poor thermal stability constitute serious drawbacks with respect to their fuel cell use.[ii],[iii],[iv] These aspects propel the search for cheaper and better alternatives. In this study membrane systems consisting of a hydrophobic poly(ethylene-alt-tetrafluoroethylene) (ETFE) backbone grafted by hydrophilic poly(styrene sulfonic acid) (PSSA) have been synthesized in a three-step procedure comprising electron beam irradiation, grafting polymerization reaction, and sulfonation. The chemical structure of the resulting ETFE-g-PSSA is shown in figure 2, and it is believed that the morphology upon hydration resembles that of the poly(perfluorosulfonic acid)s. The stability of the material has been improved by crosslinking by divinylbenzene (DVB) and by inferring methyl- and tert-butyl substituents on the styrene aromatic ring. It has been found that crosslinking by divinylbenzene clearly improves the chemical stability of both sulfonated styrene- and methylstyrene/t-butylstyrene-grafted ETFE membranes. However, the crosslinking reduces the proton conductivity due to decreased water uptake, thus downgrading the membranes' electrolytic properties. Grafting with a fraction of DVB in the order of 1-2 vol-% of the total monomers seems to be advantageous for both of the two grafting systems as a compromise between high chemical stability and good proton conductivity of the final membrane. The use of methylstyrene and t-butylstyrene as grafting monomers instead of styrene gives the resulting membranes a significantly increased chemical stability, while a reasonable proton conductivity can still be obtained. Both membrane systems show a smaller methanol uptake than water uptake.[i] Kreuer, K.-D.; Paddison, S. J.; Spohr, E.; Schuster, M.; Chemical Reviews 104 (2004) 4637-4678[ii] Skou, E.; Kauranen, P.; Hentschel, J.; Solid State Ionics 97 (1997) 333-337[iii] Fuel Cell Handbook; Seventh Edition; EG&G Technical Services, Inc.; 2004; p. 3.1-3.25[iv] Doyle, M.; Rajendran, G. in Handbook of Fuel Cells - Fundamentals, Technology, and Applications, Volume 3: Fuel Cell Technology and Applications: Part 1 (edited by Vielstich, W.; Lamm, A.; Gasteiger, H. A.); John Wiley & Sons Ltd; Chichester; 2003; p. 351-395
KW - Brændselscelle, membran, polymerelektrolyt, podning, tværbinding, alkylsubstitution, fluorpolymer, ETFE, styren, divinylbenzen, DVB, methylstyren, tert-butylstyren, t-butylstyren
KW - Fuel cell, membrane, polymer electrolyte, grafting, crosslinking, alkyl substitution, fluoropolymer, ETFE, styrene, divinylbenzene, DVB, methylstyrene, tert-butylstyrene, t-butylstyrene
M3 - Poster
ER -