Ohmic Potential Drop at Electrodes Exhibiting Steady-State Diffusion Currents

Theory shows that all (micro)electrodes exhibit the same ohmic potential drop provided they are In a steady-state dlffuslonal regime and the cell geometry would yield the electrodes's primary resistance. Laplace's equation describes both the steady-state diffusion and the resistance In such electrochemical cells. This experimental situation can be realized using microelectrodes whose dimensions are small enough to obtain dtffuslonal steady state before natural convection occurs. Expressions are derived for the ohmic potential drop occurring during voltammetry. Two limiting cases are discussed, the electrolysis of a pure binary electrolyte and a binary electrolyte In the presence of a large excess of supporting electrolyte. The results are Independent of solvent and of the geometry of the microelectrode provided the diffuse double layer Is small compared to the diffusion layer thickness.