Optimizing underwater plasma discharges: Role of electrode geometry and electrical design

Abstract

This study investigates the optimization of underwater plasma discharges by examining the influence of electrode geometry and electrical design on contaminant removal efficiency. A plasma-chemical reactor capable of igniting multiple discharges within a solution was developed, utilizing iron and molybdenum electrodes to explore the electrical characteristics and energy distribution among discharge channels. Experimental results revealed that increasing the number of electrodes enhances discharge frequency, with the two-discharge configuration exhibiting the highest energy efficiency for chemical processes, including radical generation and hydrogen peroxide formation. Notably, the majority of input energy was dissipated as Joule heating; however, the two-discharge system demonstrated a reduced thermal gradient, favoring chemical reactions over thermal losses. Testing with a model dye-contaminated solution showed optimal degradation efficiency for the two-discharge setup, attributed to the synergistic effects of reactive species generation and electrode-derived oxide structures. Molybdenum electrodes, despite yielding lower hydrogen peroxide concentrations, achieved significant dye removal due to their high sorption capacity. These findings underscore the importance of discharge topology in reactor design, suggesting that sequential discharge architectures represent a promising approach to maximize oxidative capacity while minimizing energy dissipation. This work provides critical insights for advancing plasma-based water treatment technologies.