SIMULATION OF 2-ELECTRON HOMOGENEOUS ELECTROCATALYSIS FOR STEADY-STATE VOLTAMMETRY AT HEMISPHERICAL MICROELECTRODES

Expanded space grid digital simulation of second-order, two-electron homogeneous electrocatalysis was extended to slow scan voltammetry at hemispherical microelectrodes. Predictions of the simulations are examined for reversible and quasireversible heterogeneous charge transfer of catalyst for a range of homogeneous catalytic rate constants (k1) and electrode radil. Working curves of catalytic efficiency vs log K1 were generated assuming reacting species with equal diffusion coefficients. As electrode radli in the <10-μm range decrease, progressively larger homogeneous catalytic rates are needed to yield analytically significant amplification of limiting currents. Simulations using hemispherical radli of (2/π)rd can be useπd to predict catalytic efficiencies for microdisk electrodes with radii rd. Simulated working curves were used to estimate a log K1 of 3.88 ± 0.55 (M−1 s−1) for electron transfer from the anion radical of 9,10-diphenylanthracene to 4,4′-dibromobiphenyl from steady-state catalytic efficiencies obtained at carbon microdisk electrodes. This value was In good agreement with 3.90 ± 0.16 M−1 s−1 found previously by cyclic voltammetry. © 1990, American Chemical Society. All rights reserved.