Adsorption of urea on the Pt(100) electrode: experiments and lattice-gas modeling

We report a complete experimental and theoretical description of urea adsorption on the Pt(100) electrode. We have used voltammetry, radiochemistry, LEED and quantitative Auger electron spectroscopy, as well as Monte Carlo simulations of a lattice-gas model developed for this study. We demonstrate that the simulation results agree well with those of our experiments. These include an ordered c(2 × 4) adsorbed urea phase and sharply peaked voltammograms. We interpret our observations as associated with a phase transition between the urea phase for potentials on the positive side of the voltammetric peak and a (1 × 1) monolayer of hydrogen phase on the negative side. The main products of this research are the lattice-gas model that describes the microscopic adsorption geometry and the effective lateral interaction energies of the urea surface species involved in the phase transition behavior.