Influence of Reaction-Induced Thermal Convection on the Electrical Currents Measured in Chronoamperometry and Cyclic Voltammetry

Electrochemical reactions invariably occur with a change in the molar volume between reactant and product, as well as a change in enthalpy. These factors give rise to convective flows driven respectively by concentration and temperature and affect the mass transport in the system, but the latter has received very little attention in the scientific literature. The present study attempts to fill this gap by quantifying the effect of thermal convection on the electrical currents in chronoamperometry and cyclic voltammetry, using the electrochemical oxidation of hexacyanoferrate (II) to hexacyanoferrate (III) as a model reaction. To this end, finite element numerical simulations of both electroanalytical techniques have been performed over a broad range of electrode radii (0.25 to 25 mm). The results presented here indicate that for chronoamperometry, convection has a substantial overall effect on the current, but thermal convection in particular is practically negligible for the studied systems. In contrast, for cyclic voltammetry performed under similar conditions, neither type of convection plays a significant role.