Numerical Solution of Mass Transfer Resistances Problem in an Electrolysis Process

The aim of this work was to establish the effect of mass transfer resistances in an electrochemical reaction carried out on the surface of an electrode by using mathematical modeling. For this purpose, it was assumed that the reaction occurs instantaneously on the surface of the electrode. This mathematical model considers the transport phenomena in the Nernst diffusion layer. Numerical predictions of the model show that when the Biot number (Bi) is small, the external resistance to the mass transfer is large, while the amount of the electroactive species reaching the electrode’s surface is small, which indicates that the process is controlled by mass transfer. In contrast, for large values of Biot number, the external resistance decreases, as the amount of electroactive species transported from bulk liquid to the electrode’s surface is large, indicating that the process is controlled by the reaction on the electrode’s surface. As a result of the application of this model, it has been found that the required dimensionless time (τ) to reach a steady state for Bi = [100 1.0 0.1] are 0.5, 1.5, and 3.0, respectively.