Understanding the chemical reactions in cathodic plasma electrolysis

Plasma electrolysis (PE) combines the characteristics of electrolysis and plasma discharges, creating high-energy-density plasmas that lead to intensive physical processes and chemical reactions on the working electrode. The authors have found that the physical processes and the chemical reactions could be decoupled under certain conditions, and a textured electrode surface could be created through a chemical-reaction-dominated process instead of an irregular porous surface produced by the physical-dominated interactions. A plasma fluid model for the chemical-reaction-dominated discharge is established with constraint conditions obtained from the experiments. This study aims to elucidate the plasma characteristics and the chemical reactions in cathodic PE. The modeling reveals that the plasma is highly electronegative, and the dominant neutral species are H₂ and O₂ dissociated from water vapor. The decoupling mechanism is attributed to the low surface tension, high viscosity and high boiling point of glycerol in the electrolyte, which suppress the localized intensive physical interactions and promote the formation of a stable vapor layer. The formation of textured surface is attributed to the anisotropic chemical etching by the reactive species generated in the plasmas.