Low coverage p(2 × 2) iodide phase on Cu(1 0 0)

Abstract

The phase behavior of specifically adsorbed iodide on Cu(1 0 0) has been studied by means of in situ scanning tunneling microscopy in particular focusing on low coverage iodide phases. Using an aqueous solution containing 10 mM KClO 4 and 1 mM KI an iodide coverage of Θ=0.4 ML is formed on Cu(1 0 0) at E=−200 mV vs. Ag/AgI. The resulting adsorbate structure can be understood in terms of a uniaxially expanded c(2 × 2) phase that can be described by a c( p × 2) unit-mesh with p=2.5. Characteristically a wavy long-range superstructure is superimposed on the atomic corrugation due to the uniaxial incommensurability of this adlayer. However, injecting only a small volume of the KClO 4/KI containing solution into an iodide free electrolyte (10 mM HCl) significantly lower surface concentrations of iodide can be realized on Cu(1 0 0) at the same potential of E=−200 mV. For the first time a low coverage p(2 × 2) halide phase could be observed under electrochemical conditions. It is assumed that the interplay between a strong corrugation of the copper–iodide interaction on the one hand and long-range electrostatic interactions between neighboring adsorbate particles on the other hand allows a stabilization of this low coverage p(2 × 2)-I phase.