Chemical synthesis and characterization of nano-crystalline palladium oxide

Abstract

Growing interest in the synthesis of palladium oxide arises from its potential use as a palladium precursor, for catalysis and as an electrode material. We report the preparation of palladium oxide by precipitation from supersaturated aqueous solutions of Pd(NO 3) 2 or PdCl 2. Theoretical modeling was carried out to ascertain the best yield of the reaction with respect to the preparation conditions, i.e. temperature, pH and ionic strength, in the PdO-HCl-NH 3-HNO 3-NaOH-H 2O system. Experiments were performed in a batch reactor, and effects of the various parameters such as the reagent flow-rates or the aging time were studied. Microstructural characterization of the resulting powders shows that only hydrated palladium oxide PdO.xH 2O is formed, with structural features ranging from polymeric entities undetectable by Photon Correlation Spectroscopy to porous aggregates containing 20 nm sized primary particles with varying degree of crystallinity. Reduction of the palladium oxide in ethanol to produce metallic palladium is also briefly discussed.