Bipolar ionomer membrane
Provided are membranes useful for electrochemical or fuel cells. A membrane may be formed of or include a sulfonated polymer whereby the sulfonated polymer is covalently or ionically associated with a multi-nitrogen containing heterocyclic molecule. The resulting membranes possess excellent ion conductivity and selectivity.
1. A membrane comprising:
a sulfonated polymer; and
a multi-nitrogen containing heterocyclic molecule, the heterocyclic molecule comprising a primary amine substituent;
wherein the primary amine is covalently or ionically bonded to a single sulfonic acid of the sulfonated polymer; and
wherein the sulfonated polymer is housed within a plurality of pores within a nonwoven or microporous support film.
2. The membrane of claim 1 wherein the heterocyclic molecule has a pKa of less than 9.0 after bonding to the sulfonated polymer.
3. The membrane of claim 1 , wherein the Gurley Air Permeability number of the membrane is greater than 86,400 sec/10 cc 0.20 in 2 .
4. The membrane of claim 1 wherein the proton resistivity of the membrane is at or below 20 ohm cm 2 .
5. The membrane of claim 1 wherein the vanadium transport of the membrane is at or below 1.1×10 −4 moles/day cm 2 in 1.0M vanadyl sulfate/3M sulfuric acid.
6. The membrane of claim 1 wherein the heterocyclic molecule is selected from the group consisting of adenine, aminoisoquinoline, aminobenzimidazole, aminoimidazopyridine, 4-aminopiperidine, and combinations thereof.
7. The membrane of claim 1 wherein the sulfonated polymer comprises at least one polymer selected from the group consisting of per(fluorosulfonic acid/polytetrafluoroethylene) copolymer, sulfonated polystyrene, sulfonated trifluoropolystyrene, sulfonated polystyrene-divinylbenzene copolymer, sulfonated styrene-butadiene, sulfonated polyparaphenylene, sulfonated poly(etheretherketone), sulfonated poly(ether-ketone-ether-ketone-ketone), sulfonated polysulfone, sulfonated poly(ethersulfone), sulfonated 2, 6-dimethyl-1, 4-phenylene oxide, sulfonated poly(phthalazinone ether ketone), sulfonated polyimides, sulfonated polyphosphazene, sulfonated polybenzimidazole, sulfonated polyphenylsulfone, poly(vinylidene fluoride)-graft-poly(styrene sulfonic acid), poly(arylene thioether ketone), poly(arylene thioether ketone ketone), sulfonated poly fluorenyl ether ketone, and combinations thereof.
8. The membrane of claim 1 wherein the sulfonated polymer is in the form of a non-porous film.
9. The membrane of claim 1 wherein the nonwoven or microporous support film comprises polytetrafluoroethylene, polysulfone, polyethersulfone, polyester, polyimide, polyamide, polyolefin, nitrocellulose, cellulose, mixed cellulose ester, or combinations thereof.
10. The membrane of claim 1 wherein the nonwoven or microporous support film has a pore cross sectional dimension of 0.01 to 1000 microns.
11. An electrochemical device comprising:
an anode;
a cathode; and
the membrane of claim 1 positioned between the anode and the cathode.
12. The electrochemical device of claim 11 wherein the membrane comprises the heterocyclic molecule on only one side.
13. The electrochemical device of claim 11 wherein the heterocyclic molecule is on the side proximal to the anode.
14. The electrochemical device of claim 11 in the form of a direct methanol fuel cell, or a battery.
15. The electrochemical device of claim 11 wherein the heterocyclic molecule is covalently connected to the sulfonated polymer via a sulfonamide, acid anhydride, or ester.
16. The electrochemical device of claim 11 in the form of a battery, the battery further comprising an anolyte and a catholyte, the anolyte and the catholyte comprising vanadium.
17. The membrane of claim 1 , wherein said heterocyclic molecule comprises at least one pendant nitrogen.
18. The membrane of claim 1 , wherein said heterocyclic molecule comprises a six membered ring.