Spatiotemporal patterns on a disk electrode: Effects of cell geometry and electrolyte properties

Spatiotemporal patterns on a disk electrode are simulated with a model for the electrodissolution of a metal that exhibits passivity; a 3-dimensional geometry with a point reference electrode is used. The two variables of the model are the potential drop across the electric double layer and the proton concentration near the surface of the working electrode. Non-local coupling among reaction sites is through the electric field. Several patterns seen previously in experiments are reproduced in the simulations and the dependence of transitions among them on system geometry, electrolyte conductivity and double layer capacitance are explored. For example, a state with an inhomogeneous oscillation is changed to one with a rotating wave as the reference electrode is moved closer to the working electrode and negative coupling develops; under other conditions the negative coupling produces anti-phase oscillations.