DIGITAL-SIMULATION OF STEADY-STATE AND NONSTEADY STATE VOLTAMMETRIC RESPONSES FOR ELECTROCHEMICAL REACTIONS OCCURRING AT AN INLAID MICRODISK ELECTRODE - APPLICATION TO EC(IRR), EC' AND CE 1ST-ORDER REACTIONS

A general algorithm based on the Hopscotch method and a conformal map is used to treat electrochemical reactions with coupled homogeneous chemical reactions occurring both at conventionally sized electrodes and at ultramicroelectrodes. A change of the dimensionless parameter p = a(nFv/RTD)1/2, where a is the radius of the electrode, v the potential sweep rate and D the diffusion coefficient, allows us to describe properly the planar and the convergent mass transfer to an inlaid disk-shaped electrode. The dimensionless parameter lambda'= ka2/D, which is a function of the sum of the chemical rate constants (k) and of the electrode radius, describes the kinetics and may be used instead of the conventional parameter lambda = k(RT/nFv). A suitable choice of the space-time grid gives accurate results, even for kinetic problems affected by stiffness difficulties. The adequacy of the implementation is established by comparison with known solutions relative to the EC(irr') EC' and CE mechanisms for two limiting cases, i.e. planar and radial mass transport conditions.