COADSORPTION OF COPPER WITH ANIONS ON PLATINUM(111) - THE ROLE OF SURFACE REDOX CHEMISTRY IN DETERMINING THE STABILITY OF A METAL MONOLAYER

The voltammetry for the underpotential deposition (UPD) of copper from aqueous sulfuric acid solution on flame-annealed Pt(111) electrodes pretreated with or in the presence of Cl-, Br-, I-, or S2- is reported. We find that the potential for the UPD of copper on Pt(111) decreases in the order Cl- > Br- > I- > S2- and is very linearly related to the standard reduction potential for the half-cell reaction CuX + e- → Cu + X-. This is consistent with the near-edge features of the observed X-ray absorption spectrum and with a model involving partial charge transfer from the adsorbed copper to the coadsorbate, which is most likely initially present on the platinum surface in a nonanionic (i.e., neutral) state. In addition, the kinetics of cooper UPD for the different cases were also found to vary linearly with the aforementioned standard potential. © 1990 American Chemical Society.