Study of oxygen and ozone reactions on surfaces previously treated by ozone

The chemical kinetics of oxygen atoms and ozone molecules were investigated in a fully-modulated DC discharge in pure oxygen gas in a borosilicate glass tube, using cavity ringdown spectroscopy (CRDS) of the optically forbidden O(3P2)→O(1D2) absorption at 630 nm. Measurements were made over a range of tube temperatures (10 °C and 50 °C) gas pressures (0.5–4 Torr) and discharge current (10–40 mA). The discharge current was square-wave modulated (on for 0.2 s and off for 1 s), allowing the build-up to steady-state and the decay in the afterglow to be studied. This paper focusses on the afterglow period. The O atom density decays non-exponentially in the afterglow, indicating a surface loss probability dependent on incident active particle fluxes. The oxygen atom absorption peak lies on a time-varying absorption continuum due (in the afterglow) to the Chappuis bands of ozone. The ozone density passes through a maximum a few 100 ms into the afterglow, then decays slowly. An existing time-resolved self-consistent 1D radial model of O2 positive column discharges was modified to interpret the new results. The ozone behaviour in the afterglow can only be modelled by the inclusion of: (1) surface production of O3 from the reaction of O2 molecules with adsorbed O atoms, (2) reactions of vibrationally-excited ozone with O atoms and with O2(a1Δg) molecules, and (3) surface loss of ozone with a probability of around 10−5.

Section: Ozone Surface Productionmentioning

confidence: 62%

Section: Surface Destruction Of Ozonementioning

confidence: 99%

Oxygen atom and ozone kinetics in the afterglow of a pulse-modulated DC discharge in pure O₂: an experimental and modelling study of surface mechanisms and ozone vibrational kinetics

Booth,

Guaitella,

Zhang

et al. 2023

“…(The subscript s denotes a surface species.) These reactions for O 3 destruction have been proposed by several researchers [6,13,25]. As will be discussed in section 4, W s is more abundant than O s and is therefore responsible for the majority of O 3 destruction on the surface.…”

Section: Description Of the Modelmentioning

confidence: 84%

“…Yanallah et al simulated O 3 production and showed that including O 3 loss reactions on the surfaces changed the electrical characteristics of the discharge [5]. Mazánková et al exposed copper and aluminum surfaces to O 3 produced by an ozonizer to study surface composition [6]. They showed that the elemental O composition of those surfaces increased after exposure to O 3 .…”

Section: Introductionmentioning

confidence: 99%

A surface mechanism for O₃ production with N₂ addition in dielectric barrier discharges

Meyer

Foster

Kushner

2023

Ozone, O3, is a strong oxidizing agent often used for water purification. O3 is typically produced in dielectric barrier discharges (DBDs) by electron-impact dissociation of O2, followed by three-body association reactions between O and O2. Previous studies on O3 formation in low temperature plasma DBDs have shown that O3 concentrations can drop to nearly zero after continued operation, termed the ozone-zero phenomenon. Including small (< 4%) admixtures of N2 can suppress this phenomenon and increase the O3 production relative to using pure O2 in spite of power deposition being diverted from O2 to N2 and the production of nitrogen oxides, NxOy. The ozone-zero phenomenon is hypothesized to occur because O3 is destroyed on the surfaces in contact with the plasma. Including N2 in the gas mixture enables N atoms to occupy surface sites that would otherwise participate in O3 destruction. The effect of N2 in ozone-producing DBDs was computationally investigated using a global plasma chemistry model. A general surface reaction mechanism is proposed explain an increase in O3 production with N2 admixtures. The mechanism includes O3 formation and destruction on the surfaces, adsorption and recombination of O and N, desorption of O2 and N2, and NOx reactions. Without these reactions on the surface, the density of O3 monotonically decreases with increasing N2 admixture due to power absorption by N2 leading to the formation of nitrogen oxides. With N-based surface chemistry, the concentrations of O3 are maximum with a few tenths of percent of N2 depending on the O3 destruction probability on the surface. The consequences of the surface chemistry are less than the effect of gas temperature without surface processes. An increase in the O3 density with N-based surface chemistry occurs when the surface destruction probability of O3 or the surface roughness was decreased.

“…(For example, the rate coefficient for the reaction of N 2 O 5 with O atom is less than 3 × 10 −22 m 3 s −1 [74].) Furthermore, the model does not include surface reactions, which can contribute to atomic species recombination [75], ozone creation and destruction [76][77][78] and NO oxidation to NO 2 [79].…”

Section: Chemical Kinetic Modelmentioning

confidence: 99%

Chemical composition of gaseous products generated by coplanar barrier discharge in air and N₂/O₂ mixtures

Trunec

Navrátil²,

Tomeková³

et al. 2022

Absolute densities of gaseous products generated by coplanar dielectric barrier discharge in N2/O2 mixtures and in ambient air were determined using Fourier transform infrared (FTIR) spectroscopy. A theoretical model containing up to four molecular absorption cross sections was used to split the peaks overlapping in the FTIR spectra. The product densities were determined for a wide range of applied input powers (100 - 400 W). Ozone (O3) and nitrogen oxides (N2O, NO, NO2 and N2O5) were identified as the stable products of the discharge in N2/O2 mixtures, HNO2, HNO3 and CO2 were steadily present in the gas coming from the discharge in ambient air. It was found that the actual product composition strongly depends on the gas temperature. At low input power with the low gas temperature, (O3 density was high and the NO and NO2 densities were very low. At a specific input power (and the gas temperature) O3 disappeared, while NO density started to increase gradually and NO2 density increased steeply. N2O5 density increased at low input power but decreased suddenly at the same temperature when O3 density decreased. The influence of the gas temperature on the discharge product composition was also confirmed by the 0D chemical kinetic model and by temperature measurement. The maximal ozone density reached approximately 2.7 × 1023 m-3 for the input power below 150 W and the gas mixture N2:O2 40:60. Density of 2.6 × 1022 m-3 was obtained for NO2 in the same gas mixture above 250 W.