CHARACTERIZATION OF MEMBRANE-ELECTRODE ASSEMBLIES FOR SOLID POLYMER ELECTROLYTE WATER ELECTROLYSIS

The development of medium size SPE(R) (Solid Polymer Electrolyte) water electrolysers requires satisfactory membrane-electrode assemblies. Pt-Nafion(R)-Pt, Pt-Ir-Nafion(R)-Pt and Pt-Ru-Nafion(R)-Pt composites have been tested for such applications. Anodic overvoltage, cathodic over-voltage and ohmic drop across the SPE(R) have been measured in the temperature range of 20 to 80-degrees-C and in the current density range 0 to 1 A cm-2. Kinetic parameters for the oxygen and hydrogen evolution reactions have been measured and compared to values obtained in aqueous acid solutions. Electrode structure has been investigated, before and after 2 500 h of continuous electrolysis at 1 A cm-2, by scanning electron microscopy, in order to check electrode stability at high current density. The effect of membrane surface etching on the roughness factors of the electrodes has also been investigated. Life tests performed on bare membranes and SPE composites at various operating pressures are presented and discussed. Results on the poisoning effect of nickel ions added to the feed water of the cells are reported.