Highly proton conductive crosslinked vinylsulfonic acid polymer electrolyte composite membranes and its preparation method for polymer electrolyte fuel cells
A highly proton conductive polymer electrolyte composite membrane for a fuel cell is provided. The composite membrane includes crosslinked polyvinylsulfonic acid. The composite membrane is produced by impregnating a mixed solution of vinylsulfonic acid as a monomer, a hydroxyl group-containing bisacrylamide as a crosslinking agent and a photoinitiator or thermal initiator into a microporous polymer support, polymerizing the monomer, and simultaneously thermal-crosslinking or photo-crosslinking the polymer to form a chemically crosslinked polymer electrolyte membrane which is also physically crosslinked with the porous support. Further provided is a method for producing the composite membrane in a simple manner at low cost as well as a fuel cell using the composite membrane.
1. A polymer electrolyte composite membrane for a fuel cell, comprising a porous polymer support and a polymer electrolyte membrane composed of polyvinylsulfonic acid crosslinked with N,N′-(1,2-dihydroxyethylene)bisacrylamide, wherein the composite membrane has a proton conductivity of 0.22 S/cm at room temperature and a methanol permeability 0.12 kg/m 2 h or less.
2. The composite membrane of claim 1 , wherein the polymer support is a hydrocarbon membrane having a porosity of 30 to 60%, a pore size of 0.05 to 0.1 μm and a thickness of 20 to 55 μm.
3. The composite membrane of claim 1 , wherein the polymer electrolyte membrane is formed from a mixed solution of 50 to 90 parts by weight of anhydrous vinylsulfonic acid at a concentration as high as 95%, 10 to 50 parts by weight of the crosslinking agent and 0.1 to 0.5 parts by weight of an initiator.
4. The composite membrane of claim 3 , wherein the initiator is selected from N,N′-azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO) as thermal initiators.
5. A method for producing a highly proton conductive polymer electrolyte composite membrane for a fuel cell, the method comprising (a) impregnating a mixed solution of vinylsulfonic acid as a monomer, with crosslinking agent N,N′-(1,2-dihydroxyethylene)bisacrylamide and an initiator into a porous polymer support, and (b) laminating the solution impregnated porous support between polyethylene terephthalate (PET) films, followed by photocrosslinking or thermal crosslinking, wherein the composite membrane has a proton conductivity of 0.22 S/cm at room temperature and a methanol permeability 0.12 kg/m 2 h or less.
6. The method of claim 5 , wherein the photocrosslinking is performed by irradiation with ultraviolet (UV) light having an energy of 30 to 150 mJ/cm 2 .
7. The method of claim 5 , wherein the thermal crosslinking is performed in an oven at 110 to 120° for 1 to 2 hours.
8. The method of claim 5 , wherein said vinylsulfonic acid is present at 50 to 90 parts by weight and said crosslinking agent is present at 10 to 50 parts by weight.