Role of operating conditions on the liquid penetration depth of reactive species delivered from plasma jets*

RF-driven atmospheric pressure plasma sources can deliver high quantities of reactive species to liquids. The reactive species can be used to drive chemical conversion processes, either directly, or in the frame of concepts such as biocatalysis. For all applications, the penetration depths of different reactive species in the liquid are important.

Here, an alteration of the COST jet [1], with an additional dielectric capillary between the electrodes, is investigated using a pseudo-1D plug flow model implemented in GlobalKin [2] in a helium-water vapour gas-phase and a 1D liquid simulation considering the reactive and diffusive species behaviour. The species densities simulated in the gas-phase serve as input for the liquid simulation. The concentrations of reactive species in the liquid, as a function of distance from the liquid surface, under variations of deposited power, humidity content, gas flow rate and the distance between the jet and the liquid surface are studied. It is shown that variable conditions affect the reactive species composition at the liquid surface, which in turn affects the penetration depth. Implications for plasma-driven biocatalysis will be discussed.

[1] S. Schüttler et al., Phys. Chem. Chem. Phys., 26, 8255-8272 (2024).

[2] A. M. Lietz and M. J. Kushner, J. Phys. D: Appl. Phys. 49, 425204 (2016).