Surface composition of CuAu single crystal electrodes determined by a coupled UHV-electrochemical approach and a Monte-Carlo simulation

Recent papers show that copper could act as an electrode capable of electrocatalysing the reduction of carbon dioxide, a major greenhouse gas. However, no fundamental studies on single crystals have been related, and although the presence of surface oxides seems to be important, little is known about the mechanism. Single crystal electrodes of Au, Cu and AuCu alloys (1, 10, and 20 at.% gold) and a 50 at.% gold polycrystal alloy have been synthesized and characterized by AES and cyclic voltammetry (CV). The segregation equilibrium was studied experimentally (using the low-energy Auger peaks of Cu and Au after deconvolution) and theoretically (with classical thermodynamics and a Monte-Carlo Metropolis approach). All the alloy electrodes show a surface enrichment in gold. The electrochemical characterization reveals that the dilution of copper by gold delays the oxidation of the electrode to more positive potentials with respect to pure copper, whereas simultaneously the reduction of protons occurs at more negative potentials than pure gold. Thanks to an electrochemical-UHV transfer system, we show that the surface composition of the electrode drastically depends on the working potential. Copyright (C) 2004 John Wiley Sons, Ltd.