OH and O radicals production in atmospheric pressure air/Ar/H₂O gliding arc discharge plasma jet

Abstract

Atmospheric pressure air/Ar/H 2 O gliding arc discharge plasma is produced by a pulsed dc power supply. An optical emission spectroscopic (OES) diagnostic technique is used for the characterization of plasmas and for identifications of OH and O radicals along with other species in the plasmas. The OES diagnostic technique reveals the excitation T x ≈5550-9000 K, rotational T r ≈1350-2700 K and gas T g ≈850-1600 K temperatures, and electron density »-´-() n 1.1 1.9 10 cm e 14 3 under different experimental conditions. The production and destruction of OH and O radicals are investigated as functions of applied voltage and air flow rate. Relative intensities of OH and O radicals indicate that their production rates are increased with increasing Ar content in the gas mixture and applied voltage. n e reveals that the higher densities of OH and O radicals are produced in the discharge due to more effective electron impact dissociation of H O 2 and O 2 molecules caused by higher kinetic energies as gained by electrons from the enhanced electric field as well as by enhanced n. e The productions of OH and O are decreasing with increasing air flow rate due to removal of Joule heat from the discharge region but enhanced air flow rate significantly modifies discharge maintenance properties. Besides, T g significantly reduces with the enhanced air flow rate. This investigation reveals that Ar plays a significant role in the production of OH and O radicals.

Examination of OH and H2O2 production by uniform and non-uniform modes of dielectric barrier discharge in He/air mixture

“…Traditional DBD develops via propagation of streamers (which at later phases determine position of filaments, provided by long enough voltage pulse duration) that have high electron energies due to very high reduced electric field values E/n in the streamer head (over 1000 Td). Production of OH in air-containing He plasma is primarily determined by reactions of dissociation of water by electron impact, dissociative excitation transfer between metastable He and water, and recombination reactions between atomic oxygen and hydrogen radicals [30][31][32][33]. Water molecules dissociation by metastable He is monotonically dependent on the reduced electric field values, and therefore determines lower OH production in the case of uniform mode discharge [34] (however, lifetime of metastable He in the presence of air/water is only few hundred ns, as evidenced by fast decay of the afterglow emission [15]).…”

NOx synthesis by atmospheric‐pressure N2/O2 filamentary DBD plasma over water: Physicochemical mechanisms of plasma–liquid interactions

“…In addition, the stronger UV emission from the N 2 second positive system may enhance the production of ions by photoionization of water molecules, which could explain the higher OH radical formation through reaction (). [ 38,65 ] Moreover, another reason for the reduction of OH radicals with the increase in content in the mixture is that OH radical can be consumed by O radical through reaction (). It should be noted that with a lower fraction of oxygen, fewer electrons will be consumed by negative ion formation, and thus the electron density is expected to be higher.…”

“…Several reports [36][37][38][39] have discussed the potential of inert gases to make stable plasmas with various types of discharges for the formation of RONS, but the temperature parameters (gas temperature, excitation temperature, rotational and vibrational temperature) are extensively modified in the presence of inert gases. Bogaerts et al [40] noticed that further improvements are needed to reach a better energy yield for NO x synthesis, where tailoring in reactor design, plasma power, gas flow, and gas temperature are important factors.…”

Bactericidal effects of plasma‐activated saline prepared by surface dielectric barrier discharge with different dielectric layers and working gases

“…The electron activated Ar to generate the metastable argon Ar*, and the energy of Ar* of 13.3 eV was responsible for dissociating H 2 O to OH (A) (R5, R6). [23,44] → e + Ar Ar*+e, (R5)…”

“…The electron activated Ar to generate the metastable argon Ar*, and the energy of Ar* of 13.3 eV was responsible for dissociating H 2 O to OH(A) (, ). [ 23,44 ] $$${\rm{e}}+\text{Ar}\to \text{Ar}* +{\rm{e}},$$$ $$${\text{Ar}* +{\rm{H}}}_{2}{\rm{O}}\to \text{Ar}+{\rm{H}}+\text{OH}({\rm{A}})\text{. }$$$…”