Phosphonated polymers, and methods of production thereof, for use as polymer electrolyte membranes (PEMs) and/or catalyst ionomeric binders for electrodes in PEM fuel cells
The present disclosure provides phosphonated polymers that can be used, for example, as polymer electrolyte membranes (PEMs) and/or catalyst ionomeric binders for electrodes in PEM fuel cells, and more particularly for high-temperature PEM fuel cells. High-temperature PEM fuel cells that use phosphonated polymers of the present disclosure suffer from reduced or no acid leaching because, in at least some examples, phosphonic acid moieties are covalently bound to the backbone of the polymers. A phosphonated polymer include a backbone having one or more aromatic monomers, with each aromatic monomer having one or more phosphonic acid groups. A phosphonic acid group may include phosphonic acid or a functional group that is hydrolysable into phosphonic acid.
1. A phosphonated polymer for use as a polymer electrolyte membrane (PEM) and/or a catalyst ionomeric binder for one or more electrodes in a PEM fuel cell, comprising:
a backbone comprising at least one aromatic monomer; and
a functional group comprising a tetrafluorophenylphosphonic acid or a tetrafluorophenylphosphonate ester.
2. The phosphonated polymer of claim 1 , wherein the at least one aromatic monomer is selected from the group consisting of:
3. The phosphonated polymer of claim 2 , wherein:
R′ is individually selected to be hydrogen, fluorine, a methyl group (CH3), or an alkyl group ((CH2)mCH3), wherein m is an integer as low as 0 and as high as 10; and
X is either oxygen or sulfur.
4. A polymer electrolyte membrane (PEM) fuel cell comprising:
an anode;
a cathode; and
a PEM positioned between the anode and the cathode, the PEM comprising a phosphonated polymer, the phosphonated polymer comprising:
a backbone comprising at least one aromatic monomer; and
a functional group comprising a tetrafluorophenylphosphonic acid or a tetrafluorophenylphosphonate ester.
5. The PEM fuel cell of claim 4 , wherein the at least one aromatic monomer is selected from the group consisting of:
6. The PEM fuel cell of claim 5 , wherein:
R′ is individually selected to be hydrogen, fluorine, a methyl group (CH3), or an alkyl group ((CH2)mCH3), wherein m is an integer as low as 0 and as high as 10; and
X is either oxygen or sulfur.
7. A polymer electrolyte membrane (PEM) fuel cell comprising:
an anode;
a cathode;
a PEM positioned between the anode and the cathode; and
catalyst ionomeric binder corresponding to at least one of the anode or the cathode, the catalyst ionomeric binder comprising a phosphonated polymer, the phosphonated polymer comprising:
a backbone comprising at least one aromatic monomer; and
a functional group comprising a tetrafluorophenylphosphonic acid or a tetrafluorophenylphosphonate ester.
8. The PEM fuel cell of claim 7 , wherein the at least one aromatic monomer is selected from the group consisting of:
9. The PEM fuel cell of claim 8 , wherein:
R′ is individually selected to be hydrogen, fluorine, a methyl group (CH3), or an alkyl group ((CH2)mCH3), wherein m is an integer as low as 0 and as high as 10; and
X is either oxygen or sulfur.
10. The phosphonated polymer of claim 1 , wherein the backbone consists essentially of two or more adjacent aromatic groups, wherein the adjacent aromatic groups are directly bonded together by carbon-carbon bonds.
11. The PEM fuel cell of claim 4 , wherein the backbone consists essentially of two or more adjacent aromatic groups, wherein the two or more adjacent aromatic groups are directly bonded together by carbon-carbon bonds.
12. The PEM fuel cell of claim 7 , wherein the backbone consists essentially of two or more adjacent aromatic groups, wherein the two or more adjacent aromatic groups are directly bonded together by carbon-carbon bonds.