CONTACT GLOW-DISCHARGE ELECTROLYSIS - A STUDY OF ITS ONSET AND LOCATION

At sufficiently high voltages a normal electrolysis switches over to a phenomenon called contact glow discharge electrolysis (CGDE) in which glow discharges take place across a gaseous envelope over either the anode or the cathode. A critical investigation on the influence of the relative anode-cathode dimensions, the relative anolyte-catholyte surface tension, the nature of the electrolyte constituents, and the polarity of the electrode on the onset and location of CGDE in aqueous media has been carried out. The mechanism of the growth of a stable vapour envelope on an electrode underneath an electrolyte during normal electrolysis has been examined in the light of the theory of hydrodynamic instabilities. Overall analysis of the results has led to the following conclusions: (a) vaporization, and not gas evolution at an electrode, is the prime requisite for the growth of CGDE in the aqueous phase; (b) an electrode-electrolyte area where the conditions help both easier vaporization and easier onset of hydrodynamic instabilities would be the location of CGDE; and (c) the nature of the glow discharges at an anode is quite different from that at a cathode.