| 摘要 |
<p>The object of the present invention is to provide a gas diffusion electrode with both increased dimensional stability and flexability and which can therefore be produced at lower cost. A further object is to provide an improved manufacturing process that is capable of producing large numbers of electrodes and MEAs at low unit cost, in high volumes and with high yields. Accordingly, there is provided a gas diffusion electrode comprising a non-woven network of fibres, one or more catalyst components and at least one polymeric substance characterised in that the catalyst component is embedded within the fibre network. Generally, the non-woven network of fibres has a density of less than 0.3 g/cm<3>, suitably less than 0.2 g/cm<3> and preferably less than 0.1 g/cm<3>. Fibres which are suitable for use in the present invention include carbon, glass, polymer, metal or ceramic fibres, preferably carbon, glass, metal or ceramic, typically of diameters in the range of 0.2 mu m to 50 mu m and with lengths from 0.05mm to 300mm, suitably 0.5mm to 150mm. If fibres other than carbon fibres or other electrically conducting fibres are used it is necessary that the catalyst component comprises carbon and optionally one or more other catalyst components such as metal or a metal supported on carbon in order that the final electrode structure is electrically conducting. The polymeric substances act as a binder to hold the electrode layer together. Depending on the polymeric substance used it may also act to provide essential electrode structural properties, such as control of the hydrophobic/hydrophilic balance. Examples of such polymers include polytetrafluoroethylene (PTFE), fluorinated ethylene-propylene (FEP), polyethylene, polypropylene, ethylene-propylene. The polymeric material can also act to provide the ionic conduction pathway in the electrode. Such proton conducting polymers are for example the perfluorosulphonic acid materials, produced by E.I. DuPont de Nemours, referred to as Nafion TM . The gas diffusion electrodes of the present invention are of use in electrochemical devices, including metal-air batteries, electrochemical gas sensors, and in electrosynthesis, and, particularly in fuel cells.</p> |
