MEMBRANE AND PROCESS
A reinforced ion-conducting membrane comprises a planar reinforcing component which comprises a porous polymer material; an ion-conducting component embedded in at least a region of the planar reinforcing component, which ion-conducting component comprises an ion-conducting polymer material; and linking groups which are chemically bonded to both the planar reinforcing component and the ion-conducting component. The reinforced ion-conducting membrane is useful as the membrane in a membrane-electrode assembly for example as used in fuel cells.
1 . A reinforced ion-conducting membrane, suitable for use in a membrane electrode assembly of a fuel cell, comprising:
a planar reinforcing component which comprises a porous polymer material;
an ion-conducting component embedded in at least a region of the planar reinforcing component, which ion-conducting component comprises an ion-conducting polymer material; and
linking groups which are chemically bonded to both the planar reinforcing component and the ion-conducting component.
2 . The reinforced ion-conducting membrane according to claim 1 , wherein the porous polymer material is a porous fluoropolymer material.
3 . The reinforced ion-conducting membrane according to claim 2 , wherein the porous fluoropolymer material is expanded polytetrafluoroethylene (ePTFE).
4 . The reinforced ion-conducting membrane according to claim 1 , wherein the ion-conducting polymer material is a partly fluorinated or perfluorinated proton-conducting polymer.
5 . The reinforced ion-conducting membrane according to claim 4 , wherein the ion-conducting polymer material is perfluorosulfonic acid polymer (PFSA).
6 . The reinforced ion-conducting membrane according to claim 1 , wherein the linking groups are chemically bonded to the planar reinforcing component via covalent bonds or via ionic bonds.
7 . The reinforced ion-conducting membrane according to claim 1 , wherein the linking groups are chemically bonded to the ion-conducting component via covalent bonds or via ionic bonds.
8 . The reinforced ion-conducting membrane according to claim 1 , wherein the linking groups are derived from a coupling agent comprising a nitrogen containing moiety.
9 . The reinforced ion-conducting membrane according to claim 8 , wherein the coupling agent is selected from ammonia, amine compounds, aminosilanes or mixtures thereof.
10 . The reinforced ion-conducting membrane according to claim 9 , wherein the coupling agent is selected from ammonia, allyl amine, trimethoxyaminopropyl silane, dihydroimidazole silane or mixtures thereof.
11 . The reinforced ion-conducting membrane according to claim 1 , wherein the linking groups are non-polymeric.
12 . The reinforced ion-conducting membrane according to claim 1 , comprising one or more further planar reinforcing components.
13 . A process for the production of a reinforced ion-conducting membrane according to claim 1 , said process comprising the steps of:
(i) reacting a planar reinforcing component comprising a porous polymer material with a coupling agent to form a modified reinforcing component;
(ii) impregnating at least a region of the modified reinforcing component with ion-conducting component comprising an ion-conducting polymer material; and
(iii) drying the resulting impregnated modified reinforcing component.
14 . The process as claimed in claim 13 , wherein the porous polymer material is a porous fluoropolymer material.
15 . The process as claimed in claim 14 , wherein the porous fluoropolymer material is ePTFE.
16 . The process as claimed in claim 13 , wherein the ion-conducting polymer material is a partly fluorinated or perfluorinated proton-conducting polymer.
17 . The process as claimed in claim 16 , wherein the ion-conducting polymer material is perfluorosulfonic acid polymer (PFSA).
18 . The process as claimed in claim 13 , wherein step (i) is carried out by exposing the planar reinforcing component to a plasma discharge in the presence of the coupling agent.
19 . The process as claimed in claim 18 , wherein the plasma discharge is generated from a precursor plasma gas selected from hydrogen, argon, oxygen, nitrogen or mixtures thereof.
20 . The process as claimed in claim 19 , wherein the precursor plasma gas is hydrogen.
21 . The process as claimed in claim 13 , wherein the coupling agent comprises a nitrogen containing moiety.
22 . The process as claimed in claim 21 , wherein the coupling agent is selected from ammonia, amine compounds, aminosilanes or mixtures thereof.
23 . The process as claimed in claim 22 , wherein the coupling agent is selected from ammonia, allyl amine, trimethoxyaminopropyl silane and dihydroimidazole silane or mixtures thereof.
24 . The process as claimed in claim 13 , wherein step (iii) is carried out at a temperature of 60-120° C.
25 . The process as claimed in claim 13 , wherein step (iii) is followed by (iv) subjecting the dried impregnated modified reinforcing component to high temperature treatment.
26 . The process as claimed in claim 25 , wherein step (iv) is carried out at a temperature in the range 150 to 220° C.
27 . A catalyst coated reinforced ion-conducting membrane comprising the a reinforced ion-conducting membrane claimed in claim 1 and a catalyst applied to one or both faces of the reinforced ion-conducting membrane.
28 . The catalyst coated reinforced ion-conducting membrane as claimed in claim 27 , wherein the catalyst is an electrocatalyst.
29 . A membrane electrode assembly comprising a reinforced ion-conducting membrane as claimed in claim 1 having electrocatalyst layers disposed either side of the membrane and gas diffusion layers contacting each of the electrocatalyst layers.
30 . A fuel cell comprising the membrane electrode assembly as claimed in claim 29 .
31 . A reinforced ion-conducting membrane obtained by a process according to claim 13 .