Proton exchange membrane material and methods of making the same
Hydrocarbon proton exchange membranes are disclosed that are composed of a material including a hydrophobic main chain, and acidic side chains. The main chain includes a polyaryl structure that is substantially free of ether linkages and also includes a fluoromethyl substituted carbon. The acidic side chains include a hydrocarbon tether terminated by a strongly acidic group, such as a fluoroalkyl sulfonate group. Chemical stability of the material is increased by removing the ether linkages from the main chain. The hydrophobic main chain and substantially hydrophilic side chains create a phase-separated morphology that affords enhanced transport of protons and water across the membrane even at low relative humidity levels. These materials are advantageous as membranes for use in fuel cells, redox flow batteries, water hydrolysis systems, sensors, electrochemical hydrogen compressors, actuators, water purifiers, gas separators, etc.
1. A proton exchange membrane material comprising a polymer according to formula I:
wherein Ar includes at least two or three aryl groups, R 1 includes a halomethyl, R 2 includes a flexible hydrocarbon tether having the structure according to formula II:
wherein R 3 comprises an acidic group comprising a sulfonate group, a phosphonate group, or a carboxylate group, wherein each of the sulfonate, the phosphonate and the carboxylate groups may be optionally substituted, and n is from 2 to about 20,
r is greater than at least about 100, and no ether group is adjacent the at least two aryl groups.
2. The proton exchange membrane material according to claim 1 , wherein the Ar including two or three aryl groups includes:
or combinations thereof.
3. The proton exchange membrane material according to claim 2 , wherein the Ar is
4. The proton exchange membrane material according to claim 1 , wherein the halomethyl comprises CF 3 .
5. The proton exchange membrane material according to claim 1 , wherein R 3 comprises a fluorophenyl sulfonate group.
6. The proton exchange membrane material according to claim 1 , wherein R 3 comprises a fluoroalkyl sulfonate group.
7. The proton exchange membrane material according to claim 1 , wherein R 3 comprises:
CF 2 CF 2 SO 3 H or SO 3 H.
8. The proton exchange membrane material according to claim 1 , wherein the polymer is the structure according to the following formula:
wherein x+y=1 and x>0.
9. The proton exchange membrane material according to claim 1 , wherein the polymer is a block copolymer or a multiblock copolymer.
10. An electrochemical energy conversion system comprising:
an anode;
a cathode; and
a proton exchange membrane disposed between the anode and the cathode,
wherein the proton exchange membrane includes a polymer comprising a structure according to formula I:
wherein:
Ar includes at least two or three aryl groups;
R 1 includes a halomethyl;
R 2 includes a flexible hydrocarbon tether having the structure according to formula II:
in which R 3 comprises an acidic group comprising a sulfonate group, a phosphonate group, or a carboxylate group, wherein each of the sulfonate, the phosphonate and the carboxylate groups may be optionally substituted, and n is from 2 to about 20; and
r is greater than at least about 100, and
wherein no ether group is adjacent the at least two aryl groups.
11. The system according to claim 10 , wherein the Ar including two or three aryl groups includes:
or combinations thereof.
12. The system according to claim 10 , wherein the halomethyl comprises CF 3 .
13. The system according to claim 10 , wherein R 3 comprises at least one of a fluoroalkyl sulfonate group or a fluorophenyl sulfonate group.