Numerical Study of Rayleigh–Benard Instability of a Binary Electrolyte in a Cell with Plane Parallel Electrodes Taking into Account the Space Charge

An electrochemical system consisting of two plane horizontal electrodes of the same metal and the interelectrode space filled with solution of a salt of this metal is considered. The conditions of emergence of Rayleigh–Benard convective instability in this system are investigated using a numerical method. Two reasons for the instability are taken into account: the buoyant force and the electrical force caused by a very small space charge formed near the electrode, at which the electrochemical reaction proceeds at the limiting diffusion current. The instability emergence conditions are characterized by critical values of two parameters corresponding to the aforementioned forces. The mutual effect of these forces on the instability emergence and an essential role of the ratio between the diffusion coefficients of electrolyte cations and anions are revealed.