Surface composition of binary alloys between Pd and Group IB metals as studied by Auger electron spectroscopy and cyclic voltammetry

Abstract

The surface composition of alloys between Pd and Group IB metals (Pd+IB alloys) was investigated on the basis of Auger electron spectroscopy (AES) and cyclic voltammetry. A correction factor for the extinction of Auger peak intensities by surface contaminants, mainly carbon, in deducing the surface composition was determined first. The applicability of this method was substantiated in the case of Pd + Au alloys by the empirical rule in the electrochemical observation that the potential of the oxygen reduction peak in the voltammograms varies linearly with the surface composition. Both AES and electrochemical analysis revealed that in Pd + Au alloy specimens treated by electrochemical oxidation-reduction cycles in 0.1 M NaOH within the potential range 0.05–1.50 V (vs. RHE) the original surface composition was maintained whereas a significant amount of surface Au enrichment took place on those specimens which were anodically polarized in 0.5 M H 2SO 4. AES analyses of the Pd+Ag and Pd+Cu alloy systems revealed that a weak degree (less than 0.1 in atomic fraction) of surface enrichment in Ag and Cu took place when they were treated by oxidation-reduction cycles in the potential ranges 0.05–1.0 and 0.05–0.50 V (vs. RHE), respectively, in 1.0 M NaOH.