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Fig. 7. Dissolution of copper from a polycrystalline gold electrode at E = +25 mV vs.

Cu/Cu2+

in 0.01 M HC104 + 0.1 M NaC104 + 10 mM Cu2+. (A) STM images; time interval between images: 3 min. Image size: 255 nm x 255 nm. (B) Number of particles as a function of dissolution time.

roughly 50% of the clusters disappear every two minutes.

The above examples of copper deposition and dissolution represent local experiments. They address the deposition on one section of the substrate and the dissolution of a specific distribution of copper clusters. These local processes can be related to the overall process, since information on the latter is available from the Faradaic current measured in the course of an experiment. Significant discrepancies between local and average kinetics are often but not always observed [13, 14]. This reflects the stochastic nature of electrochemical kinetics on the mesoscopic scale, but there are also systematic deviations, which indicate that the local kinetics may be influenced by the tunneling tip. The elucidation of this influence, which has up to now only been addressed qualitatively, is crucial for the understanding of electrochemical processes on the mesoscopic scale.

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