Surface segregation of silver atoms on Au–Ag alloys according to data of laser-heating induced temperature potential shifts, XPS and conventional electrochemical methods

Process of the surface segregation of Ag atoms at the interface of Au–Ag alloy electrodes with the surface inactive electrolyte (NaF) was studied in the potential region of ideal polarizability by the methods of potential shifts induced by laser heating, impedance and cyclic voltammetry. It was shown that impedance measurements on electrodes with the mechanically renewed surface make it possible to obtain well reproducible data on the kinetics of enrichment of the electrode surface layer with silver atoms. As follows from analysis of capacitance vs. potential dependences measured at different moments after the electrode renewal, these dependences are well described by the model of “common diffuse layer”. The use of this model allowed us to calculate the time dependences of the electrode surface coverage by silver atoms after renewal. Specific features of the influence of the electrode potential on the kinetics of the surface segregation of Ag atoms at the Au–Ag electrode surface were demonstrated and analyzed within the framework of the bulk diffusion model. Data for the metal/solution interface were supplemented by the XPS data for Au–Ag/vacuum interface.