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

Abstract

O 2 and CO 2 Dielectric Barrier Discharges (DBD) were studied at elevated (i.e., above atmospheric) pressure regimes (1-3.5 bar). It was demonstrated that these operational conditions significantly influence both the discharge dynamics and the process efficiencies of O 2 and CO 2 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 (10-300 nm iron oxide nanoparticles) on the reactor walls. Somewhat similar behavior was observed also for the CO 2 DBD. The discharge current, the relative intensity of the CO Angstrom band measured by Optical Emission Spectroscopy (OES) and the CO 2 conversion rates could be stimulated to some extent by the rise in pressure. The optimal conditions for the O 2 DBD (P = 2 bar) and the CO 2 DBD (P = 1.5 bar) 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.

Plasma Technology for CO2 Conversion: A Personal Perspective on Prospects and Gaps

“…On the other hand, as mentioned above, the reduced electric field can also be lowered by a higher gas number density, and this should be easier to realize, i.e., by applying a higher gas pressure (above 1 bar). This was for instance demonstrated by Belov et al (2017), resulting in a higher CO 2 conversion at 1.5 bar compared to 1 bar (30% vs. 25%). However, a further increase in pressure did not result in a higher CO 2 conversion because other effects play a role as well, as the higher pressure also resulted in more intense but fewer microdischarge filaments.…”

Excitation and relaxation of the asymmetric stretch mode of CO2 in a pulsed glow discharge

“…More specifically, the most efficient reduction channel is considered to be the uppumping of the asymmetric stretch vibration toward the dissociation limit, resulting in only a little excess energy in the form of heat [1][2][3]. Over the recent years, researchers have studied this topic extensively [4], both numerically [5][6][7][8][9][10][11][12][13] and experimentally [14][15][16][17][18][19][20][21][22][23][24][25][26], often including the CO 2 vibrations in the discussion.…”