CONCENTRATION IMPEDANCES STUDY OF A COPPER ELECTRODISSOLUTION MECHANISM

The concentration impedances of electrolyte species involved in an electro-chemical reaction taking place on a rotating disk electrode are not always classical convective diffusion impedances expressed as R th(taup)1/2/(taup)1/2. They are classical when the flux of the species at the interface is proportional to the faradaic current density. The concentration impedances of the electrolyte species are however more complicated when the structure of the reaction mechanism is such that this condition is not satisfied. A mechanism for the anodic dissolution of a metal, one of the simplest mechanisms presenting this property, has been investigated. For certain values of kinetic parameters and electrode potential, it is nevertheless possible to obtain impedance diagrams comprising an arc with a shape that is analogous to that of a convective diffusion impedance.