Dynamics of the dissolution of an underpotentially deposited Cu layer on Au(111): a combined time-resolved surface-enhanced infrared and chronoamperometric study

It is well known that an ordered phase consisting of 2/3 monolayer (ML) of Cu and 1/3 ML of sulfate is formed by the underpotential deposition of Cu o n Au(111) in sulfuric acid. Dynamic processes involved in the dissolution o f the ordered phase for a potential step have been investigated by time-res olved surface-enhanced infrared absorption spectroscopy (SEIRAS) and chrono amperometry. The results demonstrate that the dissolution occurs through tw o successive steps. The initial step involves the desorption of 1/3 ML of C u and 1/3 ML of sulfate via a Langmuir-type kinetics and the remaining 1/3 ML of Ca is desorbed in the subsequent step via a nucleation-and-growth kin etics. The observation is partly consistent with dynamic Monte Carlo simula tions reported in the literature. (C) 2000 Elsevier Science S.A. All rights reserved.