Electrodes for alkaline fuel cells with circulating electrolyte

#1. Field of the Invention

#The present invention relates to novel electrode structures which are of use in electrochemical devices, particularly fuel cells, and it teaches new processes for the manufacture of electrode and stack designs. The invention improves also alkaline direct methanol fuel cells.

#2. Description of Related Art

#The invention is further illustrated in the Figures, in which:

#FIG. 1 is a schematic view of a porous electrode;

#FIG. 2 shows cathodic potential (versus zinc) versus current density relating to Example 1;

#Fuel cell electrodes have been designed which comprise a non-woven network of conductive fibers (like carbon fleece, nickel foam sheet or stainless steel wool layer), plus additional activated carbon material, carrying one or more catalyst components and at least one polymeric substance as binder and/or repellancy agent to establish three zone interfaces (liquid-solid-liquid) or three phase interfaces (gas-liquid-solid), whereby the electroactive catalyzed material is embedded into the conductive structure by specified deposition processes (coating, blading or spraying). The specific catalyst density of the finished electrodes is within the range of 0.8 mg/cm3 to 50 mg/cm3 (per vol.) or 0.1 mg/cm2 to 2.0 mg/cm2 (per area) and the overall density of the finished electrodes is within the range of 50 mg/cm2 to 150 mg/cm2 (per area).

#The inventive fuel cell electrodes comprise a non-woven network of conductive fibres and catalyzed active carbon material treated with one or more polymers as binders and/or surface-tension controlling agents, such hydrophobic binders (agents), including materials like polytetrafluoroethylene, fluorinated ethylene-propylene, polyethylene, polypropylene, ethylenepropylene and polyisobutenes, and hydrophilic (wetting) binders, including polysulfones and epoxy resins. The binders are selected for use in combination that assure the proper hydrophobic/hydrophilic balance of the electrode, which provides the optimum ionic conduction pathway in the electrode.

#Fuel cell electrodes according to the invention may comprise a non-woven network conductive fibres and catalyzed active carbon material, whereby the carbon material is steam- or CO2 activated Vulcan XC-72, or a mix with carbon black or graphite and the catalysts are selected