Ionic mass transfer on fixed disk and conical electrodes under streaming solutions—I. Theoretical approach

S.L Marchiano,A.J Arvía

doi:10.1016/0013-4686(67)80117-8

Abstract

A solution of the convective-diffusion differential equation for the case of disk and conical electrodes axially placed in laminar flow is attempted. The integration of the equations is done with an approximate streaming function which is valid for values of the function up to 0·3 within an error of one per cent.The rate equation for a steady convective-diffusion process on the disk electrode isj = 0·780Di(Uvr)12 Sc13(Ci0-Cis).The type of solution is then extended to the case of conical electrodes with axial symmetry. A similar equation is thus obtained and the numerical coefficients for the average rate equation are in agreement with the one of the above equation, within 4 per cent, and are independent of the cone angle. The latter result agrees also with a previous equation deduced by analogy with the corresponding heat-transfer problem.

Highlights

THERE are various possibilities for increasing the rate of mass transfer in electrochemical reactions
One of the more detailed studies refers to the rotating disk electrode where the corresponding convective-diffusion dilferential equation has been satisfactorily solved[1] on the basis of a known exact solution of the hydrodynamic equations. 8~8 This electrode presents a uniformly accessible reaction surfaq[4] from the standpoint of diffusion
In the literature several attempts are mentioned where an increase of the rate of mass transfer was achieved by flowing the electrolyte solution while the working electrode was static.- One of these refers to an arrangement of a conical electrode under a streaming solution

Summary

INTRODUCTION

THERE are various possibilities for increasing the rate of mass transfer in electrochemical reactions. The present study has a double purpose: first, to attempt the solution of the convective-diffusion differential equation for either fixed disk or conical electrodes in flowing solutions, to obtain an explicit function relating the current density with the variables which affect the rate of ionic mass transfer comprising the solution for tied disk electrodes as a limiting case of the problem of conical electrodes; secondly, to verify experimentally the theoretical deductions. The former aspect is reported in this Part I and the latter in Parts II and III. This second solution is extended to conical electrodes and compared and correlated with that for the disk-type tied electrode

THE FIXED DISK ELECTRODE

I I 6 I

Findings

APPLICATION TO ELECTROCHEMICAL