Kinetics of Cu underpotential deposition on iodine-modified Au(111) electrodes

Abstract

The kinetics of copper underpotential deposition (UPD) on Au(I 11) previously covered with an iodine adlayer were investigated by means of cyclic voltammetry (CV) and chronoamperometry (CA) techniques in an aqueous solution containing I MM CuSO4 and 0.05 M H2SO4. Characterization of the deposition process was based on quantitative analysis of the potentiostatic current-time curves recorded during Cu UPD. It was found that the deposition behavior can be well described by a model that involves three types of contributions: (i) a Langmuir-type adsorption process with two different kinds of two-dimensional nucleation mechanisms, (ii) an instantaneous, and (iii) a progressive contribution, the latter two limited by lattice incorporation of adatoms. It is shown that the main effect of the iodine adlayer is to slow the kinetics of Cu UPD when compared to the same process in the absence of an iodine adlayer. Results from CV also reveal a very stable iodine adlayer even after several Cu deposition/stripping cycles, requiring a high positive potential when surface oxidation takes place in order remove it from the Au(I 11).