Stationary Potential Patterns during the Reduction of Peroxodisulfate at Ag Ring Electrodes

Abstract

The potential distribution in front of a Ag ring electrode during the reduction of peroxodisulfate was measured with potential microprobes. Inhomogeneous stationary potential distributions were observed when using a Haber-Luggin capillary, i.e., placing the reference electrode close to the working electrode on the axis of the ring. It is shown that such an arrangement introduces a negative global coupling into the system which destabilizes homogeneous stationary states if the current-potential characteristics exhibits a negative differential resistance. Further consequences of the negative global coupling are discussed, and the effect of an additional, external series resistor is demonstrated.

Experiments on arrays of globally coupled chaotic electrochemical oscillators: Synchronization and clustering

“…22 In electrochemical systems a nonlocal coupling among reactive sites arises through the electric field; potential changes at some location are transmitted rapidly to other locations. [23][24][25][26][27] This coupling is long-range but is not global because its effect dies out with increasing distance. In addition, a global coupling can be imposed on eleca͒ Permanent address: Institute of Physical Chemistry, Kossuth Lajos University, Debrecen H-4010, Hungary.…”

Pattern Formation in the Belousov−Zhabotinsky Reaction with Photochemical Global Feedback

“…Many types of spatial patterns have been found in theoretical and experimental studies of chemical systems with GNF. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Antiphase oscillations were first discovered in the electrochemical dissolution of nickel under galvanostatic conditions. 11 Later, antiphase oscillations of fixed spatial domains were seen in other electrochemical systems with global feedback.…”

Experimental and Model Spatiotemporal and Spatial Patterns in Electrochemical Systems

“…Reprinted with permission from [22] http://link.aps.org/abstract/PRE/v51/p3997. Copyright 1995 by the American Physical Society illustration of such interplay of couplings was reported by Grauel et al [24] for the electroreduction of S 2 O 8 2À at Ag ring electrodes, for the parameter values close to or corresponding to the bistable characteristics of that process, and with the LugginHaber capillary minimizing the ohmic potential drop. Figure 2.8 shows the distribution of the electrode potential, varying as a function of time, along the ring Ag electrode (i.e., for the angle varying from 0 to 2p).…”

“…This is because external serial resistor introduced a positive global coupling which counteracted the negative global coupling and thus the formation of patterns. These experimental results were successfully modeled in terms of the appropriate equivalent circuits, where variation of external resistance tuned the relative contribution of the negative and positive global couplings [24].…”

“…Sect. 2.2) [24] cannot be classified as Turing ones. As described earlier, in the case of peroxodisulfate reduction, the formation of two spatial domains on the working electrode was due to the negative global coupling, caused by the external circuit, and not only by the migrations of ions in the electrolyte which is one of the major factors deciding the emergence of Turing patterns.…”