Simplified methods for preparing a catalyst coated membrane (CCM) for solid polymer electrolyte fuel cells. The CCM has two reinforcing, expanded polymer sheets and the methods involve forming the electrolyte membrane from ionomer solution during assembly of the CCM. Thus, the conventional requirement to obtain, handle, and decal transfer solid polymer sheets in CCM preparation can be omitted. Further, CCM structures with improved mechanical strength can be prepared by orienting the expanded polymer sheets such that the stronger tensile strength direction of one is orthogonal to the other. Such improved CCM structures can be fabricated using the simplified methods.

To provide an electrolyte membrane that exhibits high proton conductivity even at low humidity, the electrolyte membrane includes a composite membrane including: a microporous polyolefin membrane that has an average pore diameter of 1 to 1000 nm and a porosity of 50 to 90% and that can be impregnated with a solvent having a surface free energy of 28 mJ/m.sup.2 or more, and an electrolyte containing a perfluorosulfonic acid polymer having an EW of 250 to 850 loaded into the pores of the microporous polyolefin membrane, wherein the membrane thickness of the composite membrane is 1 to 20 ?m.

An embodiment ionomer for a fuel cell includes a copolymer having no carbon-oxygen bond, wherein the copolymer includes hydrophilic moieties disposed at both ends, wherein each hydrophilic moiety includes a styrene unit and a proton conductive functional group, and a hydrophobic moiety interposed between the hydrophilic moieties, wherein the hydrophobic moiety includes an ethylene-based unit, a butylene-based unit, an isoprene-based unit, or any combination thereof.

Disclosed is a method for post-treating a polybenzimidazole-based separator before assembling the separator to an electrode assembly, the method including: providing the polybenzimidazole-based separator; heat-treating the polybenzimidazole-based separator at 60 to 180? C.; and cooling the heat-treated polybenzimidazole-based separator to room temperature.

A method for making a composite membrane includes the steps of coating a first layer of ionomer on an intermediate support, laminating a dry porous support into the wet first layer of ionomer, impregnating the porous support with ionomer from the coated ionomer layer, optionally drying the impregnated porous support and the first layer of ionomer, coating a second layer of ionomer on the impregnated porous support, drying the second layer of ionomer until most of the solvent is evaporated, and delaminating the composite membrane from the intermediate support. The composite membrane thus obtained includes a porous support impregnated with the ionomer and on each side of the impregnated support a dense ionomer layer.

Alkaline-stable cations were introduced to a polyolefin bearing phenyl side chains to enable manipulation of ion exchange capacity and hot pressing technique. Hydroxide exchange membranes or hydroxide exchange ionomers formed from these polymers exhibit superior chemical stability, hydroxide conductivity, decreased water uptake, good solubility in selected solvents, and improved device stability as compared to conventional hydroxide exchange membranes or ionomers. Hydroxide exchange membrane fuel cells and hydroxide exchange membrane electrolyzers comprising the polyolefin with pendant cation provide enhanced performance and durability at relatively high temperatures.

The method of making a nanocomposite polyelectrolyte membrane is a process for forming membranes for use in hydrogen and methanol fuel cell applications, for example. A hydrophobic polymer, such as polypropylene, is blended with a nanofiller, such halloysite nanotubes (HNTs) or propylene-grafted maleic anhydride nano-layered silica (Ma-Si), to form a dry mix, which is then pelletized for extrusion in a twin-screw extruder to form a thin film nanocomposite. The thin film nanocomposite is then annealed and cold stretched at room temperature. The cold stretching is followed by stretching at a temperature ranging from approximately 110 C. to approximately 140 C. The nanocomposite is then heat set to form the nanocomposite polyelectrolyte membrane. The nanocomposite polyelectrolyte membrane may then be further plasma etched and impregnated with a sulfonated polymer, such as sulfonated melamine formaldehyde, a polycarboxylate superplasticizer or perfluorosulfonic acid.

A method of fabricating a composite membrane, includes the steps of: forming a first solution comprising a charged polymer and a first uncharged polymer having a repeat unit of a formula of: ##STR00001##
where each of X and Y is a non-hydroxyl group; forming a second solution comprising a second uncharged polymer; electrospinning, separately and simultaneously, the first solution and the second solution to form a dual fiber mat; and processing the dual fiber mat to form the composite membrane.

Simplified methods are disclosed for preparing a catalyst coated membrane that is reinforced with a porous polymer sheet (e.g. an expanded polymer sheet) for use in solid polymer electrolyte fuel cells. The methods involve forming a solid polymer electrolyte membrane by coating membrane ionomer solution onto a first catalyst layer and then applying the porous polymer sheet to the membrane ionomer solution coating, while it is still wet, such that the membrane ionomer solution only partially fills the pores of the porous polymer sheet. A second catalyst ink is then applied which fills the remaining pores of the porous polymer sheet. Not only are such methods simpler than many conventional methods, but surprisingly this can result in a marked improvement in fuel cell performance characteristics.

To provide a simple method whereby an ionic polymer membrane having a high ion exchange capacity and a low water uptake can be produced by converting a SO.sub.2F group in a polymer to a pendant group having multiple ion exchange groups, while preventing a cross-linking reaction. At the time of obtaining an ionic polymer membrane by converting SO.sub.2F (group (1)) in a polymer sequentially to SO.sub.2NZ.sup.1Z.sup.2 (group (2)), SO.sub.2N.sup.(M.sub..sup.+)SO.sub.2(CF.sub.2).sub.2SO.sub.2F (group (3)), SO.sub.2N.sup.(H.sup.+)SO.sub.2(CF.sub.2).sub.2SO.sub.2F (group (4)) and SO.sub.2N.sup.(M.sub..sup.+)SO.sub.2(CF.sub.2).sub.2SO.sub.3.sup.M.sub..sup.+ (group (5)), the polymer is formed into a polymer membrane in the state of any one of the groups (1) to (4), and the polymer membrane is thermally treated in the state of group (4). Here, Z.sup.1 and Z.sup.2 are hydrogen atoms, etc., M.sub..sup.+ is a monovalent cation, and M.sub..sup.+ is a hydrogen ion or a monovalent cation.