SPATIOTEMPORAL PATTERN-FORMATION DURING THE REDUCTION OF PEROXODISULFATE IN THE BISTABLE AND OSCILLATORY REGIME - A SURFACE-PLASMON MICROSCOPY STUDY

Using surface plasmon microscopy we demonstrate that oscillations as w ell as transitions in the bistable regime during the reduction of S2O8 2- at Ag electrodes are accompanied by wave phenomena. Typical velocit ies of the waves range from some centimeters per second to meters per second, depending on the conductivity of the electrolyte. The characte ristic length of the patterns is determined by the temporal dynamics o f the potential drop across the double layer at high mass transport an d by the dynamics of the concentration of S2O82- at the electrode at l ow mass transport. The first gives rise to potential fronts with front widths between 0.1 and 0.5 mm; the second leads to smooth structures on the order of centimeters. Further, the influence of the electrode b oundary on the pattern formation in electrochemical systems is discuss ed, as well as the generality of the above-mentioned characteristic ti mes and lengths.