B. Martuzans and Yu. Skryl
In the paper the numerical solution of Nernst–Planck equations is considered taking into account the Poisson equation. The proposed difference scheme was used to solve a pair of problems with two components: the ambipolar diffusion and the liquid junction. It is shown that the concentration level critical for the Planck condition depends on the concentration gradient to the power 2/3. This dependence allows one to estimate the applicability of the Planck condition to different electrochemical systems.