Characterization of Discharge Types during Cathodic Plasma Electrolysis

In-liquid plasma electrolysis refers to the ignition of a plasma in a thin vapor layer surrounding a solid electrode immersed in a liquid electrolyte and its associated processes. Over the last century, this phenomenon has been described under various names and is frequently denoted as Contact Glow Discharge Electrolysis. Previous works could show that the plasma might not solely consist of a glow that extends through the entire vapor layer, as the name implies, but consists of multiple filamentary discharges. Building on our previous work on the statistical evaluation of such discharges (J. Phys. D: Appl. Phys. 58 (2025) 215204), here we study the discharge properties, such as their general appearance, gas temperature, electron density, current density, electron production mechanism, and the discharge voltage, using optical emission spectroscopy, scanning electron microscopy imaging, and electrolyte potential measurements. Our results indicate that the discharges do not solely consist of glow discharges. Instead, the possible co-existence of other discharges, such as arcs and sparks, is discussed.