AN EXPLICIT FINITE-DIFFERENCE SIMULATION FOR CHRONOAMPEROMETRY AT A DISK MICROELECTRODE IN A CHANNEL FLOW SOLUTION

An explicit finite difference simulation is used to describe chronoamp erometry at a disk microelectrode in a channel flow solution. All know n phenomenologically important processes are represented in the simula tion, including the electrode ''edge effect'' in all three spatial dim ensions and the parabolic flow profile of a viscous liquid in a channe l. The simulation was achieved with the use of an exponentially expand ing spatial grid and a variable time increment to minimise the computa tional requirements. The simulation was used to study the effects of e lectrode radius, solution velocity and channel thickness on both the n ear steady-state limiting current (I(lim)nss) and the time taken to ac hieve the near steady-state condition (t(nss)) for a reversible one-el ectron charge transfer process. It was found that the solution velocit y 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 sol ution velocity. The relationships between I(lim)nss or t(nss) and solu tion velocity were found to be non-linear. The results of the simulati on compared favourably with experimental data obtained from the limiti ng current region of near steady-state voltammograms for the reversibl e oxidation of ferrocene at platinum disk microelectrodes of radii ove r the range 5-50 mum.