Dr. Rajeshwar Singh

Abstract:

Contact glow discharge electrolysis (CGDE) is a novel electrochemical phenomenon in which gas plasma is maintained by dc glow discharges between one of the electrodes and the surrounding electrolyte in a conventional electrolysis cell setup.The phenomenon develops either cathode/anode spontaneously in course of ordinary electrolysis whenever the voltage applied is sufficiently high. The transition from ordinary electrolysis to CGDE is marked by a significantly large drop in the current with simultaneous appearance of a luminous gaseous sheath over the cathode or the anode. CGDE can be observed in aqueous, man aqueous or molten electrolytes whenever the conditions for its formation are favorable. This novel electrolysis is an example of electrochemical processes across a plasma-electrolyte interface in contrast to a solid-electrolyte interface in conventional electrolysis. The chemical effects of CGDE are, not surprisingly, remarkably different from those of ordinary electrolysis. The products are novel for ordinary electrolysis and their yields exceed significantly the Faraday law values. The phenomenon has been reported in the literature off and on since its first reporting in 1844, and described by various terms such as anode effect, aqueous anode effect electrode effect, glow electrolysis galvanoluminescence, electrode glow besides contact glow discharge electrolysis.

A closely related phenomenon where electrochemical processes too occur at a plasma electrolyte interface is ‘glow discharge electrolysis (GDE)’. As compared to CGDE, GDE has been investigated much more extensively. In this technique, one of the electrodes (called the gas plasma electrode) usually the anode is placed above the liquid electrolyte and a glow discharge is passed from the electrode to the surface of the electrolyte. It is distinguished from CGDE in that one of the electrodes is located in the gas space in contrast to that both the electrodes are dipped into the liquid electrolyte during CGDE. However, there are interesting similarities in the chemical effects of CGDE and GDE. The Products obtained at the glow discharge electrode in either phenomenon are novel for normal electrolysis and the yields are remarkably deviated from those stipulated by Faraday’s laws. Different aspects of CGDE have drawn the attention of many investigators. Origin, chemical effects, spectroscopy of light emission is the principal aspects of investigation. CGDE is a potential tool for generating OH radical, H radicals, metallic nano-particles and heat treatment of metal useful for dental implants.