Underpotential deposition of Cu on Au(111) in sulfate-containing electrolytes: a theoretical and experimental study

摘要

We study the underpotential deposition of Cu on single-crystal Au(111)electrodes in sulfate-containing electrolytes by a combination of computationalstatistical-mechanics based lattice-gas modeling and experiments. Theexperimental methods are in situ cyclic voltammetry and coulometry and ex situAuger electron spectroscopy and low-energy electron diffraction. Theexperimentally obtained voltammetric current and charge densities and adsorbatecoverages are compared with the predictions of a two-component lattice-gasmodel for the coadsorption of Cu and sulfate. This model includes effective,lateral interactions out to fourth-nearest neighbors. Using group-theoreticalground-state calculations and Monte Carlo simulations, we estimate effectiveelectrovalences and lateral adsorbate--adsorbate interactions so as to obtainoverall agreement with experiments, including both our own and those of othergroups. In agreement with earlier work, we find a mixed R3xR3 phase consistingof 2/3 monolayer Cu and 1/3 monolayer sulfate at intermediate electrodepotentials, delimited by phase transitions at both higher and lower potentials.Our approach provides estimates of the effective electrovalences and lateralinteraction energies, which cannot yet be calculated by first-principlesmethods.