ROTATING HEMISPHERICAL ELECTRODE - ACCURATE EXPRESSIONS FOR THE LIMITING CURRENT AND THE CONVECTIVE WARBURG IMPEDANCE

The laminar boundary layer equations describing the steady-state axisy mmetric fluid motion near a spherical surface are solved numerically b y considering a series expansion of the colatitude theta limited to te n 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 theta with ten terms. This calculation also provi des 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, takin g into account the Schmidt number correction. The impedance results ar e experimentally confirmed over a wide range of dimensionless frequenc y (6 x 10(-3) less than or equal to p less than or equal to 1).