Surface segregation of bismuth atoms in Ag-Bi alloys (based on results obtained by traditional electrochemical methods and the laser heating-induced temperature potential shift)

Abstract

The time effects observed on mechanically renewed electrodes of eutectic-type Ag–Bi alloys in NaF solutions in the potential range of ideal polarizability are studied by traditional electrochemical methods: cyclic voltammetry and electrochemical impedance spectroscopy. The observed effects are shown to be a result of surface segregation of Bi atoms (enrichment of the metal surface layer by these atoms) realized at a rate very high as compared with usual solid-state processes. The analysis of these data carried out in the framework of phenomenological models made it possible the assumption that the mechanism of surface (not bulk) diffusion is responsible for the “anomalously” high rate of electrode surface enrichment with Bi atoms to be substantiated. The additional information on the segregation processes at the interface of Ag–Bi electrode with NaF solution acquired by the method of laser heating-induced temperature potential shift correlates with the results of electrochemical investigations.