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 on Au(111) in sulfuric acid. Dynamic processes involved in the dissolution of the ordered phase for a potential step have been investigated by time-resolved surface-enhanced infrared absorption spectroscopy (SEIRAS) and chronoamperometry. The results demonstrate that the dissolution occurs through two successive steps. The initial step involves the desorption of 1/3 ML of Cu and 1/3 ML of sulfate via a Langmuir-type kinetics and the remaining 1/3 ML of Cu is desorbed in the subsequent step via a nucleation-and-growth kinetics. The observation is partly consistent with dynamic Monte Carlo simulations reported in the literature.