Poly(aryl piperidinium) polymers with pendant cationic groups are provided which have an alkaline-stable cation, piperidinium, introduced into a rigid aromatic polymer backbone free of ether bonds. 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 mechanical properties in an ambient dry state as compared to conventional hydroxide exchange membranes or ionomers. Hydroxide exchange membrane fuel cells comprising the poly(aryl piperidinium) polymers with pendant cationic groups exhibit enhanced performance and durability at relatively high temperatures.

Described herein is a polymer-electrolyte-membrane fuel cell (PEMFC) that incorporates a shunt into the membrane separator that becomes electronically conductive around a well-defined anodic onset potential, thereby preventing excessive anodic potentials at the positive electrode that would otherwise drive deleterious parasitic reactions such as catalyst dissolution or catalyst and carbon oxidation.

Described herein is a polymer-electrolyte-membrane fuel cell (PEMFC) that incorporates a shunt into the membrane separator that becomes electronically conductive around a well-defined anodic onset potential, thereby preventing excessive anodic potentials at the positive electrode that would otherwise drive deleterious parasitic reactions such as catalyst dissolution or catalyst and carbon oxidation.

The copolymer includes divalent units represented by formula —[CF.sub.2—CF.sub.2]—, at least one divalent unit represented by formula (I): and at least one divalent unit independently represented by formula (II): A is —N(RF.sup.a).sub.2 or a is non-aromatic, 5- to 8-membered, perfluorinated ring comprising one or two nitrogen atoms in the ring and optionally comprising at least one oxygen atom in the ring, each RFa is independently linear or branched perfluoroalkyl having 1 to 8 carbon atoms and optionally interrupted by at least one catenated O or N atom, each Y is independently —H or —F, with the proviso that one Y may be —CF.sub.3, h is 0, 1, or 2, each i is independently 2 to 8, and j is 0, 1, or 2. A catalyst ink and polymer electrolyte membrane including the copolymer are also provided.

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Membrane electrode assembly and method for fabricating the same. In one embodiment, the method may involve providing an anion exchange membrane and then applying catalyst coatings to opposing surfaces of the anion exchange membrane, whereby a membrane electrode assembly may be formed. Next, the membrane electrode assembly may be subjected to a two-part treatment process. In a first part of the process, the membrane electrode assembly may be swelled, at room temperature, by exposure to an aqueous ethanol solution vapor while being retained under tension in a frame. The aqueous ethanol solution vapor may be, for example, 80:20 by volume ethanol and water. In a second part of the process, the swollen membrane electrode assembly may be removed from the frame and then pressed, at room temperature, between two plates. A layer of rubber and a layer polytetrafluoroethylene may be placed between each plate and the swollen membrane electrolyte assembly.

A membrane electrode assembly that can enhance power generation performance, and a polymer electrolyte fuel cell. The membrane electrode assembly for use in a polymer electrolyte fuel cell according to an aspect of the present invention includes a polyelectrolyte membrane, a fuel electrode-side electrocatalyst layer, and an oxygen electrode-side electrocatalyst layer. The fuel electrode- and oxygen electrode-side electrocatalyst layers and contain voids which include pores having a diameter in the range of 3 nm or more and 5.5 μm or less. When the integrated pore volume for all the pores in the fuel electrode- and oxygen electrode-side electrocatalyst layers and is a first integrated volume, the value obtained by dividing the first integrated volume by the mass of the catalytic material contained in both of the electrocatalyst layers is in the range of 2.8 or more and 4.5 or less.

A membrane electrode assembly that can enhance power generation performance, and a polymer electrolyte fuel cell. The membrane electrode assembly for use in a polymer electrolyte fuel cell according to an aspect of the present invention includes a polyelectrolyte membrane, a fuel electrode-side electrocatalyst layer, and an oxygen electrode-side electrocatalyst layer. The fuel electrode- and oxygen electrode-side electrocatalyst layers and contain voids which include pores having a diameter in the range of 3 nm or more and 5.5 μm or less. When the integrated pore volume for all the pores in the fuel electrode- and oxygen electrode-side electrocatalyst layers and is a first integrated volume, the value obtained by dividing the first integrated volume by the mass of the catalytic material contained in both of the electrocatalyst layers is in the range of 2.8 or more and 4.5 or less.

A protonated dimeric ionic liquid that enhances and improves the performance of a fuel cell catalyst. The protonated dimeric ionic liquid comprises 9′9′-(butane-1, 4-diyl)bis(3,4,6,7,8,9-hexahydro-2H-pyrimido[1,2-a]pyrimidin-1-ium) 1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonate (HTBD) Membrane electrode assemblies (MEAs) and polymer electrolyte membrane fuel cells (PEMFCs) employing the protonated dimeric ionic liquid are also disclosed.

A protonated dimeric ionic liquid that enhances and improves the performance of a fuel cell catalyst. The protonated dimeric ionic liquid comprises 9′9′-(butane-1, 4-diyl)bis(3,4,6,7,8,9-hexahydro-2H-pyrimido[1,2-a]pyrimidin-1-ium) 1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonate (HTBD) Membrane electrode assemblies (MEAs) and polymer electrolyte membrane fuel cells (PEMFCs) employing the protonated dimeric ionic liquid are also disclosed.

A dimeric ionic liquid that enhances and improves the performance and durability of a fuel cell catalyst. The dimeric ionic liquid comprises 1,1-(butane-1,4-diyl)bis(9-methyl-3,4,6,7,8,9-hexahydro-2H-pyrimido[1,2-a]pyrimidin-1-ium 1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonate (D-[MTBD][C.sub.4F.sub.9SO.sub.3]). Membrane electrode assemblies (MEAs) and polymer electrolyte membrane fuel cells (PEMFCs) employing the dimeric ionic liquid are also disclosed.