Underpotential deposition of copper and silver on single crystal surfaces of rhodium

A brief review of the field of underpotential deposition (UPD) processes in the theory/modeling perspective is given, and new insights into the UPD of copper and silver on Rh(1 1 1) and Rh(1 0 0) in perchloric and sulfuric acid media are reported. Voltammetric results show a clear dependence of the UPD shift on Rh substrate geometry and on the type of the electrolyte used. For copper, we identified one peak on Rh(1 0 0) and two peaks on Rh(1 1 1), separated by 210 and 350 mV in perchloric and sulfuric electrolytes, respectively. Preliminary XPS experiments were performed to investigate some specific aspects of copper deposition processes. Overall, we report a strong effect of the anion adsorption on positions of Cu UPD peaks, with the effect being more noticeable on Rh(1 1 1) than on Rh(1 0 0). In the experiments with silver on Rh(1 1 1), multiple peaks were obtained, whereas no Ag UPD peak was found either on Rh(1 0 0) or on polycrystalline Rh. In addition, we found that the Ag UPD process on Rh(1 1 1) is dependent on silver concentration. As indicated in the paper Tables, except for Cu UPD on Rh(1 0 0), there is a major deviation from the linear relationship between the UPD shift and the difference between the work function of the substrate and that for the underpotentially deposited adatoms.