Operating mechanism of the electrolyte cathode atmospheric glow discharge

Abstract

Cathode fall (U _cf ), cathodic current density and atomic emission intensities originating from metal salts in the electrolyte cathode were measured as a function of different discharge parameters. Emission intensities in function of cathode fall indicate a potential barrier in the sputtered mass flux. This means that the primary particles of the cathode sputtering are of positive charge and the cathode fall including its internal variables is the most important factor. The measured current density and the U _cf as a function of pressure are in accordance with the low pressure data in the literature. The observed decrease of the U _cf with decreasing pH was explained by a model in that the secondary electron emission coefficient of the cathode (γ) is controlled through a reaction net of competing reactions of different electron scavengers involving the hydroxonium ions of the cathode solution. The model revealed two different electron emission processes of the electrolyte cathode, an emission coupled with hydrated electrons is dominating below pH 2.5 while a proton-independent emission of poor efficiency is working above pH 3. Our model fits to the reported yields of the ultimate products both in the solution and in the gas phase and offers a calculation of γ and U _cf in the function of the cathode acidity. The model provides two other independent γ calculation methods based on product analysis data.