An explicit finite difference simulation for chronoamperometry at a disk microelectrode in a channel flow solution

Abstract

An explicit finite difference simulation is used to describe chronoamperometry at a disk microelectrode in a channel flow solution. All known phenomenologically important processes are represented in the simulation, including the electrode “edge effect” in all three spatial dimensions and the parabolic flow profile of a viscous liquid in a channel. The simulation was achieved with the use of an exponentially expanding spatial grid and a variable time increment to minimise the computational requirements. The simulation was used to study the effects of electrode radius, solution velocity and channel thickness on both the near steady-state limiting current ( I lim nss) and the time taken to achieve the near steady-state condition ( t nss) for a reversible one-electron charge transfer process. It was found that the solution velocity had a dramatic effect on both I lim nss and t nss, with an increase in I lim nss and decrease in t nss being observed with increased solution velocity. The relationships between I lim nss or t nss and solution velocity were found to be non-linear. The results of the simulation compared favourably with experimental data obtained from the limiting current region of near steady-state voltammograms for the reversible oxidation of ferrocene at platinum disk microelectrodes of radii over the range 5–50 μm.