Mechanism of the Breakdown of Normal Electrolysis and the Transition to Contact Glow Discharge Electrolysis

The question of how normal electrolysis (NE) at high voltages breaks down and transforms into contact g-low discharge electrolysis (CGDE) was addressed with the anode as the preferred center for the phenomenon. Because close analogies in physical characteristics exist in the NE-to-CGDE transition and the natural convection-to-stable film boiling transition observed during pool boiling of liquids, the applicability of Helmholtz Taylor's boiling heat transfer theory to the breakdown of NE and the transition to CGDE was examined. The approach was justified by the proportionality relationships observed between the critical flux of heat dissipated by the Joule effect near the anode and the anolyte surface tension or the radius of the anode wire. The results led to a detailed mechanism of the transition of NE to CGDE at the anode consisting of the following sequences: local solvent vaporization, setting up of stable counterflows between the vapor bubbles and the liquid anolyte at the anode, collapse of this flow pattern and formation of an unstable vapor film with an overlying heavier liquid, stabilization of the vapor film, and incipience of glow discharges across the film. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3186023] All rights reserved.