Abstract: The invention herein relates to a PEM fuel cell stack consisting of one or more superimposed fuel cells (1), each containing a membrane electrode assembly (2) and electrically conductive bipolar plates (3, 4), whereby the membrane electrode assemblies each comprise a polymer electrolyte membrane (5), which is in contact on each side with a reaction layer (6, 7); whereby the reaction layers cover a smaller area than the polymer electrolyte membrane, and between each reaction layer and the adjacent bipolar plates—essentially congruent with the reaction layers—respectively one compressible gas distribution layer (8, 9) of carbon fiber material is provided, and gaskets (11, 12) are interposed in the region outside the area covered by the gas distribution layers; whereby the gas diffusion electrodes formed by the reaction layers and the gas distribution layers exhibit a no-load thickness of D1 and the gaskets a thickness D2.

Abstract: A process is disclosed for applying electrode layers to a polymer electrolyte membrane strip in a desired pattern, wherein the front and back of the membrane are continuously printed with the electrode layers in the desired pattern using an ink containing an electrocatalyst, and the printed electrode layers are dried at elevated temperature immediately after the printing operation, the printing taking place while maintaining accurate positioning of the patterns of the electrode layers on the front and back in relation to one another.

Abstract: A PEM fuel cell stack including one or more fuel cells (1) arranged on top of one another, each of which contains a membrane electrode assembly (2) between two electrically conductive bipolar plates (3,4), the surfaces of which are equipped with flow channels (10) open on one side for the supply of reactive gases, whereby the membrane electrode assemblies each comprise a polymer electrolyte membrane (5), both sides of which are in contact with a reaction layer (6,7), whereby the surface area of the reaction layers is smaller than that of the polymer electrolyte membrane and a compressible, coarse-pore gas distribution layer (8,9) made from carbon fiber fabric is inserted between each reaction layer and the adjacent bipolar plates congruent to the reaction lawyers along with seals (11,12) in the area outside the surface covered by the gas distribution layers, whereby the gas distribution layers in the no-load condition display a thickness D1 and the seals a thickness D2.

Abstract: A gas diffusion structure for polymer electrolyte fuel cells having a sheet-like carbon substrate made hydrophobic and having two main opposing surfaces and a contact layer on one of these surfaces. The contact layer is formed of an intimate mixture of at least one hydrophobic polymer, which can be polyethylene, polypropylene or polytetrafluoroethylene, and finely divided carbon particles, wherein the weight percentage of the carbon particles relative to the total weight of the contact layer amounts to 40 to 90 wt. %. The gas diffusion structure is a carbon substrate made hydrophobic by at least one hydrophobic polymer and the hydrophobic polymers are restricted to two layers extending from both opposing surfaces into the carbon substrate down to a depth of from 5 to 40 &mgr;m and the hydrophobic polymers fill of from 20 to 60% of the pore volume within those layers.

Abstract: A membrane electrode unit for polymer electrolyte fuel cells consisting of a polymer electrolyte membrane, both faces of which are in contact with porous reaction layers and gas distributor layers. The reaction layers contain noble metal catalysts supported on carbon and a proton-conducting polymer, a so-called ionomer. At least one of the two reaction layers also contains a noble metal black.

Abstract: An ink is disclosed for producing membrane electrode assemblies for fuel cells which contains a catalyst material, an ionomer, water and an organic solvent. The ink is characterized in that the organic solvent is at least one compound from the group of linear dialcohols with a flash point higher than 100° C. and is present in the ink in a concentration between 1 and 50 wt. %, with respect to the weight of water.

Abstract: A membrane-electrode unit for polymer-electrolyte fuel cells. The membrane-electrode unit consists of a polymer electrolyte membrane and porous reaction layers applied to both sides comprising a catalyst and a proton-conducting polymer, a so-called ionomer. The membrane-electrode unit is characterized in that one part A1 of the catalyst of the reaction layers is saturated with the ionomer and is embedded in the ionomer whereas one part A2 of the catalyst is kept free from the ionomer, where the parts A1 and A2 are in a weight ratio of 1:1 to 20:1.

Abstract: A catalyst layer on a substrate material which contains a proton-conducting polymer (ionomer), electrically conductive carbon particles and fine particles of at least one precious metal. The catalyst layer is obtainable by coating the substrate material with an ink which contains a dispersion of the carbon particles and at least one organic precious metal complex compound in a solution of the ionomer, and drying the coating below a temperature at which the ionomer or the substrate material is thermally damaged, the precious metals in the complex compounds being present with an oxidation number of 0 and the complex compounds being thermally decomposed during drying to form the fine precious metal particles.

Abstract: A stable paste for fired-on layers which produces few pyrolysis products contains 0.3 to 3 wt. % of polyethylenimine as binder. The binder inhibits sedimentation of the contents of the paste.

Abstract: A porous gas diffusion electrode for membrane fuel cells on an ion-conducting polymer. The electrode contains a finely divided electrocatalyst which is dispersed in a proton-conducting ionomer and has a total porosity of more than 40 to less than 75%. It supplies considerably improved performance data in comparison to known electrodes. The electrode can be produced by using pore-forming materials which are dissolved during the re-protonation of the ion-conducting polymers with sulfuric acid or are decomposed by the action of temperature.