Membrane for fuel cell, and fuel cell incorporating that membrane
View Patent ↗A proton exchange membrane for a fuel cell is prepared from a polyimidazole polymer having the formula: wherein R 1 -R 3 are independently H, a halogen, an alkyl or a substituted alkyl. X 1 and X 2 are independently or an electron withdrawing group such as CN. The membrane may be doped to alter its conductivity. The membrane may be prepared from a copolymer of the polyimidazole. Also disclosed is a fuel cell incorporating the membrane.
1. A fuel cell having a proton exchange membrane, said membrane comprising a polyimidazole polymer of the type:
wherein n is a positive integer, R 1 -R 3 are independently H, a halogen, alkyl, or a substituted alkyl; and wherein X 1 and X 2 are independently H or an electron withdrawing group; said membrane including a silicon compound therein.
2. The fuel cell of claim 1 , wherein X 1 and X 2 are each CN.
3. The fuel cell of claim 1 , wherein said membrane further includes a polar solvent dissolved therein.
4. The fuel cell of claim 3 , wherein said polar solvent is selected from the group consisting of N-methylpyrrolidone, dimethylformamide, dimethylsulfoxide, and combinations thereof.
5. The fuel cell of claim 1 , wherein said membrane further includes a dopant therein.
6. The fuel cell of claim 1 , wherein said dopant comprises a strong acid.
7. The fuel cell of claim 6 , wherein said strong acid is selected from the group consisting of nitric acid, phosphoric acid, polyphosphoric acid, sulfuric acid, and combinations thereof.
8. The fuel cell of claim 6 , wherein said strong acid is an organic acid.
9. The fuel cell of claim 1 , wherein said membrane comprises a copolymer of said polyimidazole polymer and another material.
10. The fuel cell claim 1 , wherein R 1 -R 3 are independently H or a C 1 -C 5 alkyl.
11. The fuel cell of claim 1 , wherein X 1 and X 2 are independently: NR 3 + , SR 2 + , NO 2 , SO 2 R, CN, SO 2 Ar, COOR, NRCOR, OR, SR, C≡CR, Ar, CR═CR 2 ; wherein R is: H, alkyl, or substituted alkyl, and wherein Ar is an aromatic group.
12. The fuel cell of claim 1 , wherein the polymer comprising said membrane has a molecular weight in the range of 5×10 3 -10 7 daltons.
13. The fuel cell of claim 1 , wherein said membrane has a thickness in the range of 25-200 microns.
14. The fuel cell of claim 1 , wherein said membrane has an electrical conductivity greater than 0.01 S/cm.
15. The fuel cell of claim 1 , wherein said membrane comprises a polyimidazole polymer which is copolymerized with an acidic monomer.
16. The fuel cell of claim 15 , wherein said acidic monomer is an acidic vinyl monomer.
17. The fuel cell of claim 16 , wherein said acidic vinyl monomer is selected from the group consisting of: vinyl phosphonic acid, vinyl sulfonic acid, styrene sulfonic acid, and combinations thereof.
18. The fuel cell of claim 1 , wherein R 1 -R 3 are fluorine.
19. The fuel cell of claim 1 , wherein said membrane includes a heteropolyacid.
20. The fuel cell of claim 19 , wherein said heteropolyacid is selected from the group consisting of: monododecylphosphate, phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, and combinations thereof.
21. The fuel cell of claim 19 , wherein said heteropolyacid is adsorbed on a carrier which is dispersed in said polymer.
22. The fuel cell of claim 21 , wherein said carrier comprises silica.
23. The fuel cell of claim 1 , wherein said silicon compound comprises SiO 2 .
24. The fuel cell of claim 1 , wherein said silicon compound comprises a network of —Si—O—Si— which extends through at least a portion of said membrane.
25. A fuel cell having a proton exchange membrane, said membrane comprising a polyimidazole polymer of the type:
wherein n is an integer, R 1 -R 3 are fluorine; and wherein X 1 and X 2 are independently H or an electron withdrawing group.
26. A fuel cell having a proton exchange membrane, said membrane comprising a polyimidazole polymer of the type:
wherein n is an integer, R 1 -R 3 are independently H, a halogen, alkyl, or a substituted alkyl; and wherein X 1 and X 2 are independently H or an electron withdrawing group; said membrane including a heteropolyacid.
27. The fuel cell of claim 26 , wherein said heteropolyacid is selected from the group consisting of: monododecylphosphate, phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, and combinations thereof.