Pressure as an additional control handle for non-thermal atmospheric plasma processes

O-2 and CO2 Dielectric Barrier Discharges (DBD) were studied at elevated (i.e., above atmospheric) pressure regimes (1-3.5bar). It was demonstrated that these operational conditions significantly influence both the discharge dynamics and the process efficiencies of O-2 and CO2 discharges. For the case of the O-2 DBD, the pressure rise results in the amplification of the discharge current, the appearance of emission lines of the metal electrode material (Fe, Cr, Ni) in the optical emission spectrum and the formation of a granular film of the erosion products (10-300nm iron oxide nanoparticles) on the reactor walls. Somewhat similar behavior was observed also for the CO2 DBD. The discharge current, the relative intensity of the CO Angstrom band measured by Optical Emission Spectroscopy (OES) and the CO2 conversion rates could be stimulated to some extent by the rise in pressure. The optimal conditions for the O-2 DBD (P=2bar) and the CO2 DBD (P=1.5bar) are demonstrated. It can be argued that the dynamics of the microdischarges (MD) define the underlying process of this behavior. It could be demonstrated that the pressure increase stimulates the formation of more intensive but fewer MDs. In this way, the operating pressure can represent an additional tool to manipulate the properties of the MDs in a DBD, and as a result also the discharge performance.