Insights into hydrogen peroxide generation and reaction chemistry at a dc plasma-liquid interface by multiphysics modeling and chemical probe characterization

The plasma-liquid interface is a complex reaction system that presents both challenges and opportunities for emerging applications in water treatment, materials synthesis, and chemical conversion. Most of the studies to date have been experimental, including spectroscopic characterization of the plasma and chemical characterization of liquid-phase species. Here, we present a multi-physics model of the plasma-liquid interface that encompasses both the plasma and plasma-liquid interface using the MOOSE-based drift-diffusion-reaction software, Zapdos-Crane. The model was used to study a humid argon dc plasma over a water electrode, with results supported by experimental measurements. In this system, one of the reactions that occurs is the formation and dissolution of hydroxide (OH) radicals, which subsequently produce hydrogen peroxide. We studied potential mechanisms for H2O2 production with the plasma operated as both the cathode and anode. From both modeling and experiments, our results reveal that H2O2 production is increased during anodic plasma treatment due to elevated water vapor dissociation reactions near the interface. Solvated electrons generated during cathodic plasma treatment are shown to directly degrade aqueous H2O2, substantially inhibiting its accumulation.