Cyclic voltammetry at microelectrodes. Influence of natural convection on diffusion layers as characterized by in situ mapping of concentration profiles

Cyclic voltammetry was performed at microelectrodes under experimental conditions where no forced convection participates to the mass transport. Mapping of the dynamic concentration profiles were achieved using a method previously described. According to the time scale of the experiments and size of the microelectrodes, the results show that several regimes may be achieved. To delineate respectively the involvement of planar diffusion, hemispherical diffusion and natural convection in the overall mass transport, the experimental voltammograms and concentration profiles were compared to simulated ones accounting for each contribution. Excellent agreement was observed between data and predictions establishing that convection influences cyclic voltammetry even at microelectrodes reputed to be immune owing to their micrometric sizes.