ИСТИНА

In the present study, the time dependences of the electrical double layer capacitance (С vs.  curves) were measured in situ on alloy electrodes from the moment of their mechanical renewal (leveling off of the bulk and surface compositions) in electrolyte solution. For Ag-Sn (up to 3 at.% Sn) and Au-Sn (1 at.% of Sn) alloys, it was shown that the time effects observed after the renewal are a result of the alloy surface layer enrichment with Sn atoms, i.e., their surface segregation. It should be noted that at the metal-solution interface, this process is realized with a rate that can be considered as “anomalously” high for solid-phase processes. As was shown by the treatment of experiment data in the framework of phenomenological models, in 20 – 40 minutes after the renewal, the surface concentration of Sn atoms reached 25 at.% for the Ag-Sn alloy and ~17 at.% for the Au-Sn alloy and then remained unchanged. These data were compared with the data obtained by electrochemical measurements under the same electrochemical conditions on electrodes prepared from intermetallic compounds Ag3Sn and Au5Sn. The results of this comparison allowed us to assume that the process of surface segregation involved the formation of intermetallic-like compounds Ag3Sn and Au5Sn, respectively, in a thin surface layer of the studied alloy electrodes.