(485a) Modeling of Voltametric Behavior of Nanostructured Electrodes

Nanostructured electrodes have become ubiquitous in fuel cells as well as other electrochemical devices.  The voltammetric response of such electrodes has typically be described using the classic model of Nicholson and Shain.  This model however assumed semi-infinite diffusion to a smooth, flat electrode surface.  Arrays of nanotubes or other similar nanostructured electrodes do not fit this category.  Such systems involve semi-infinite diffusion to the outer surface of the nanostructured electrode as well as diffusion within the electrode layer itself.  The widely used, classic models do not account for this diffusion within the nanostructure.  As a result, many different conclusions have been drawn about the nature of the performance of various nano-electrodes.  We present a model of nanostructured electrode performance with two distinct regions: a semi-infinite region representing the bulk electrolyte, and thin-film layer representing the nanostructured region. The results predict a constant thin layer diffusivity lower than the bulk diffusivity due to the nature of the nanostructure array region; hindered pore diffusion. The resulting current-potential relationship is fit to cyclic voltammetric data for a Pt nanotube array for the common potassium ferrocyanide redox reaction whose bulk diffusivities and electron rate transfer parameters are already accepted in literature. The analysis provides fundamental insight, accounting for both kinetic and mass transfer effects in the nanostructured array.