Preparation, characterization and catalytic properties of perfluorosulfonated ion-exchange membranes containing surface-concentrated, hydrated ruthenium oxide particles

Abstract

Microparticulate hydrated ruthenium oxide precipitates have been prepared in Nafion ion-exchange membranes by treatment of the Ru-exchanged membranes with KOH or NaOH solutions. These precipitates are concentrated near both membrane surfaces giving a concentration profile which depends on the conditions of preparation. The particle size, nature and distribution across the membrane thickness of the precipitates were characterized by scanning electron microprobe analysis, transmission electron microscopy, electron microdiffraction and X-ray diffraction. The oxide is present as very fine crystalline spherical particles whose size ranges from 200 to 1000 Å. Precipitation was also achieved at one side only in free-standing membranes with ruthenium oxide at one side and uranium oxide at the other. Nafion-coated modified electrodes containing precipitated ruthenium oxide particles catalyse the oxidation of water to oxygen and the reduction of oxygen to hydrogen peroxide and water in the presence of mediators. The relevance of these results to the construction of solid polymer electrolyte devices containing active electrocatalysts is discussed.