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 configuratio n. The system consists of a metal disk electrode located at the bottom of a hollow cylinder with insulating walls. On the electrode surface a dissolut ion-precipitation mechanism is assumed to occur in the presence of a salt h im. A model is formulated based on boundary value problem for Laplace equat ion and the equations of conservation of charge and mass balance. The bound ary value problem is transformed to an infinite set of ordinary differentia l equations and solved numerically. The spatio-temporal response is present ed for four different cases, namely, relaxation oscillations, complex oscil lations, excitability and bistability. It is shown that during relaxation o scillations the whole electrode surface oscillates in a homogeneous manner while in the remaining cases non-homogeneities cause complex spatial behavi or. Within the excitable and bistable regions under spatial perturbations l ocated at the center of the disk, the electrode surface turns from the pass ive 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 E lsevier Science Ltd. All rights reserved.