Rotating Hemispherical Electrode: Accurate Expressions for the Limiting Current and the Convective Warburg Impedance

Abstract

The laminar boundary layer equations describing the steady‐state axisymmetric fluid motion near a spherical surface are solved numerically by considering a series expansion of the colatitude θ limited to ten terms for each velocity component. The velocity expansions are used in the steady‐state mass balance equation to obtain concentration as a series expansion of θ with ten terms. This calculation also provides the Schmidt number correction to the steady‐state current density. Finally, the unsteady state mass balance equation is solved to obtain the convective Warburg impedance of an hemispherical electrode, taking into account the Schmidt number correction. The impedance results are experimentally confirmed over a wide range of dimensionless frequency .