Interactions at the Interface between Atmospheric Pressure Pasmas and Liquids

Low temperature atmospheric pressure plasmas (APPs) interfacing with liquids have been extensively investigated in the context of plasma-aided decomposition of recalcitrant organic pollutants in water, plasma medicine and material synthesis. These applications leverage the unique ability of APPS to deliver large fluxes of highly reactive plasma species to liquids. Nonetheless, the strong non-linear coupling between the plasma and liquid phase leads to complex interfacial interactions which remain not well understood and have a major impact on the plasma properties and species fluxes impinging on the liquid. For example, liquid evaporation can lead to significant changes in the plasma composition, and sheaths and boundary layers have length scales of 100 μm or less leading to significant diagnostics challenges. Furthermore, atmospheric pressure plasmas are prone to instabilities introducing high spatial and temporal variations in plasma properties and dynamics.



In this presentation, we will report time resolved measurements of the development of plasma instabilities in pulsed discharges with a liquid electrode and describe the underpinning mechanisms that can trigger or prevent the formation of such instabilities in the presence of a liquid electrode. We will discuss the impact of plasma-induced liquid evaporation on the discharge morphology and reactive species formation, and show that with a detailed knowledge of the gas phase OH and electron densities near the liquid interface, we can quantitatively explain plasma-induced redox reactions with probe molecules in the solution phase for specific cases. Several examples of reactions enabled by plasma-induced solution electrochemistry with significant promise for chemical synthesis will be shown and a few case studies of unexplored liquid phase reactions will be presented.