Kinetics of CuEtX film formation on copper piezoelectrodes

The interactions of ethylxanthate ions (EtX−) with copper electrodes were investigated using voltammetric, potential step, and nanogravimetric techniques. It has been found that chemisorption of EtX− ions on copper is followed by a multi-layer CuEtX film growth at sufficiently positive potentials. The growth mechanism of the anodic films has been elucidated and a kinetic equation proposed. The increasing irreversibility of the film formation/reduction processes has been found for films with thicknesses increasing from 2 to 10 monolayers (ML). The analysis of the phenomenological kinetic equation shows that a relatively large loss of the potential driving force, ca. 27 mV ML−1, strongly inhibits the CuEtX film growth at increasing film thickness. The electroreduction of thicker CuEtX films is also strongly retarded and the electrodissolution rates approach 0.42 ng cm−2 s−1 at E=−700 mV versus SCE. At high cathodic overpotentials (E=−1200 mV), a dielectric breakdown of the film with instantaneous and complete film removal was observed. The film disintegration was manifested by a positive spike on the apparent mass transients. The implications of the appearance of apparent mass spikes in dynamic film conversions have been discussed and the use of an electrochemical quartz crystal nanobalance as a diagnostic tool in studies of film dynamics proposed.