Electrochemical oscillations in a hollow cylinder: spatio-temporal response

The spatio-temporal behavior of an electrochemical oscillator during anodic dissolution is studied theoretically for a specific geometric configuration. The system consists of a metal disk electrode located at the bottom of a hollow cylinder with insulating walls. On the electrode surface a dissolution-precipitation mechanism is assumed to occur in the presence of a salt him. A model is formulated based on boundary value problem for Laplace equation and the equations of conservation of charge and mass balance. The boundary value problem is transformed to an infinite set of ordinary differential equations and solved numerically. The spatio-temporal response is presented for four different cases, namely, relaxation oscillations, complex oscillations, excitability and bistability. It is shown that during relaxation oscillations the whole electrode surface oscillates in a homogeneous manner while in the remaining cases non-homogeneities cause complex spatial behavior. Within the excitable and bistable regions under spatial perturbations located at the center of the disk, the electrode surface turns from the passive to an active state through a potential front. Once on an active state, the system returns to its final stale via a potential front starting on the center of the disk and propagating along the electrode surface. (C) 2000 Elsevier Science Ltd. All rights reserved.