Prof. Eckhard Spohr, Lehrstuhl für Theoretische Chemie Universität Duisburg-Essen D-45141 Essen, Germany
A reactive trajectory approach for the study of proton discharge at charged metal surfaces is discussed. It is based on an extension of a minimalistic empirical valence bond (EVB) model to study proton transfer in the bulk. Quantum mechanical density functional theory calculations were parametrized for the EVB force _eld. The model is used to investigate reactive (discharging) proton trajectories that were started in the bulk of a water _lm adsorbed on charged metal electrodes. We study the electrochemically active Pt(111) surface un- der various conditions.For pure water in contact with the electorde, the results indicate a transition between a reaction-dominated regime at moderate negative charges, where the rate constant increases ex- ponentially, to a \transport limited" regime where the transfer rate is almost independent of the surface charge density (at more nega- tive surface charge densities). For NaCl electrolyte solutions, proton discharge depends both on the bulk concentration (screening) and on adsorbed ions (site blocking and spolvent ordering).