Galvanic displacement of copper adatoms on platinum in PtCl42- solutions

The kinetics of interaction of copper adatoms Cuad on polycrystalline Pt (pc Pt) with PtCl42- (0.5 M H2SO4 supporting electrolyte) at open circuit is studied. Hidden currents of Cuad displacement (ihidCu) are compared with exchange currents of Cu2++2e⇄CuadCu2++2e⇄Cuad reaction determined by the impedance method and also with hidden currents of platinum deposition on pc Pt under open-circuit conditions. The substantial excess of ihidCu high θCu over the Pt deposition currents (in absence Cuad) is attributed to the “direct” chemical interaction between PtCl42- and Cuad. The anomalous increase in ihid with increasing potential at small θCu is explained by the involvement of adsorbed oxygen forms in the displacement process. CVA and transients of open-circuit potential are measured on the Pt(1 1 1) electrode. For measurements “in the solution meniscus”, the displacement process on Pt(1 1 1) and pc Pt was shown to be largely diffusion controlled.