NL7607469A - Porous electrode for electrochemical cells - has porous conductive layer with a binder, esp. of PTFE and an ion exchange layer with the same binder - Google Patents

Abstract

Porous electrode contains a porous electrically conductive layer contg. a binder, in contact with an ion exchange layer contg. the same binder as the conductive layer. The two layers may be in direct contact, or they may make contact via an intermediate layer which contains the same binder as the other two layers. Pref. the binder is a polymeric material, esp. PTFE, and the concn. of binder in the electrically conductive layer is 5-50 wt. %, esp. 8-30 wt. %, and in the ion exchange layer 5-50 wt. %, esp. 5-15 wt.%. The electrically conductive layer is pref. sufficiently porous to allow permeation of gases and liquids, but is sealed with a gas-permeable, liquid-tight layer of the same material as the binder in the electrically conductive and ion exchange layers. The electrodes are useful in electrochemical cells in which >=1 of the materials is gaseous, whereby one side of the electrode is in contact with the gas and the other side with a suitable electrolyte, so that the electrode reactions occur in the pores in the region of the gas/liq. contact interface. The ion exchange layer protects the electrode against penetration of harmful ions from the electrolyte into the electrochemically active material. In particular, the fuel cell may be run on air contg. CO2, which causes the formation of carbonate ion in the electrolyte, which has previously caused a deterioration in the electrochemical processes in the cell. The electrodes have high mechanical strength so that the chance of parting of the layers in use, is overcome. The electrodes can be made easily by standard methods, and can be made very thin so that the internal resistance of the electrode can be lower than when using unbonded ion exchange membranes.