Effect of intermittent convection movements on voltammogram and current transients

摘要

The influence of intermittent convection movements on electrochemical voltammograms is investigated. When the bath temperature rises to 315 K, the voltammograms exhibit irregular plateaus that differ for independent voltammetry scans, even when the setup is maintained under exactly the same conditions. In this paper, we show that such behavior can be caused by convection movements that develop in the electrolytic cell as a consequence of velocity fluctuations, since no bubbles or regular convective patterns are observed at this temperature. Theoretical current-potential curves for the heterogeneous deposition of metals on silicon electrodes is derived from a model consisting of a one-dimensional balance equation that includes diffusion, convection, and reaction through a time-dependent boundary condition. We obtain the current density associated with the adsorption of particles on the surface and, through this expression, we consider the effect of constant convective velocities on voltammograms. Finally, we examine the effect of random convective movements, described by a Monte Carlo algorithm that takes into account the random temporal fluctuations around a null convective current. The model predicts accentuated fluctuations on the current profiles, especially on the current plateaus that correspond to a stationary current regime. The validity of the theoretical model is checked against experimental data. (c) 2008 American Institute of Physics.