Abstract: The invention relates to the field of electrochemical cells and fuel cells, more specifically to polymer-electrolyte-membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC). A multi-layer membrane-electrode-assembly (ML-MEA) comprising two electrically conductive bipolar plates and a membrane-electrode-assembly (MEA) bonded together by means of an electrically insulating adhesive material is disclosed. The adhesive material, preferably a polyurethane-based system, is in direct contact with the protective film layers attached to front side and the back side of the MEA, thus contamination of the ionomer membrane and/or the electrode layers with adhesive components is avoided. Multi-layer MEAs with improved long term stability and life time are obtained. The products are used for the manufacture of low temperature PEMFC and DMFC stacks.

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: The invention relates to the field of electrochemical cells and fuel cells, more specifically to polymer-electrolyte-membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC). A multi-layer membrane-electrode-assembly (ML-MEA) comprising two electrically conductive bipolar plates and a membrane-electrode-assembly (MEA) bonded together by means of an electrically insulating adhesive material is disclosed. The adhesive material, preferably a polyurethane-based system, is in direct contact with the protective film layers attached to front side and the back side of the MEA, thus contamination of the ionomer membrane and/or the electrode layers with adhesive components is avoided. Multi-layer MEAs with improved long term stability and life time are obtained. The products are used for the manufacture of low temperature PEMFC and DMFC stacks.

Abstract: The present invention relates to the field of electrochemical cells and fuel cells, more specifically to polymer-electrolyte-membrane (PEM) fuel cells and describes a process for the manufacture of membrane-electrode-assemblies (MEAs) containing five layers. The five-layer MEA is assembled together by means of a lamination process involving an adhesive component. The anode gas diffusion layer, the catalyst-coated membrane and the cathode gas diffusion layer are combined together by a low temperature/low pressure lamination process. Handling of the MEAs and assembly of the products into PEMFC and DMFC stacks is simplified. Less damage and perforation of the catalyst-coated membrane occurs and thus the performance of the five-layer MEAs is significantly improved.

Abstract: The invention comprises a process for making a membrane electrode assembly comprising a polymer electrolyte membrane having two opposite faces, on each face of which is applied a catalyst layer and a gas distribution layer. The two gas distribution layers in the membrane electrode assembly are formed by hydrophobized carbon substrates which, using appropriate inks containing at least one catalyst, dissolved ionomer and solvent, are each coated with a catalyst layer and are then laid on opposite faces of the polymer electrolyte membrane with the catalyst layers still in the moist state. Afterwards, a firm bond between electrolyte membrane, catalyst layers and carbon substrates is produced by treating the membrane electrode assembly at elevated temperature under pressure.

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: The present invention relates to the field of electrochemical cells and fuel cells, more specifically to polymer-electrolyte-membrane (PEM) fuel cells and describes a process for the manufacture of membrane-electrode-assemblies (MEAs) containing five layers. The five-layer MEA is assembled together by means of a lamination process involving an adhesive component. The anode gas diffusion layer, the catalyst-coated membrane and the cathode gas diffusion layer are combined together by a low temperature/low pressure lamination process. Handling of the MEAs and assembly of the products into PEMFC and DMFC stacks is simplified. Less damage and perforation of the catalyst-coated membrane occurs and thus the performance of the five-layer MEAs is significantly improved.

Abstract: The invention comprises a process for making a membrane electrode assembly comprising a polymer electrolyte membrane having two opposite faces, on each face of which is applied a catalyst layer and a gas distribution layer. The two gas distribution layers in the membrane electrode assembly are formed by hydrophobized carbon substrates which, using appropriate inks containing at least one catalyst, dissolved ionomer and solvent, are each coated with a catalyst layer and are then laid on opposite faces of the polymer electrolyte membrane with the catalyst layers still in the moist state. Afterwards, a firm bond between electrolyte membrane, catalyst layers and carbon substrates is produced by treating the membrane electrode assembly at elevated temperature under pressure.

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 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: 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.