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

Abstract

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.

Influence of Gas Temperature on Gaseous Products Generated by Coplanar Barrier Discharge in Air and N2/O2 Mixtures

“…Besides N 2 O 5 and N 2 O molecules, HNO 3 with the pronounced part of the cross section within 180-240 nm can contribute to the UV light absorption in humid air plasma. Nevertheless, the similarity between curves b and c suggests that the nitric acid is not present at 200 W, in agreement with the FTIR measurement [3]. Power dependencies of the O 3 and NO 2 densities are along with the results of FTIR spectroscopy [3] shown in Figure 4.…”

“…Nevertheless, the similarity between curves b and c suggests that the nitric acid is not present at 200 W, in agreement with the FTIR measurement [3]. Power dependencies of the O 3 and NO 2 densities are along with the results of FTIR spectroscopy [3] shown in Figure 4. In order to improve the image clarity, very low densities obtained by OAS and FTIR are not shown in the plot.…”

“…However, OAS enables fast measurements in time, which was used for the measurement of discharge products after immediate change of discharge power (see next subsection). Typical optical absorption spectra, measured at specific powers and in molecules also fall in this region, they were not observed, as their densities (see the results of FTIR measurement in [3]) as well as their absorption cross sections were significantly lower than those of O 3 . Due to almost complete light extinction around O 3 absorption maximum (at 254 nm), the measured absorbance in this wavelength region is weighted with a large error.…”

Evaluation of Selected Properties of Dielectric Barrier Discharge Plasma Jet

“…On the other hand, the amount of generated NO x compounds is relatively small, which is also consistent with only a slight pH drop. Despite the possibility of interaction with nitrogen N 2 present in the atmospheric air surrounding the discharge [ 75 ], plasma occurs mainly in the working gas, the components of which are transferred along with the stream to the liquid but the energy delivery is much weaker here than in more powerful plasma discharges, e.g., mini-gliding arc or transient spark [ 7 , 67 ]. Due to the small concentrations of nitrogen compounds and the more complex chemistry involved in both the liquid reactions and the reagents used to determine their concentrations, the results are not as well reproducible as for H 2 O 2 .…”

Extension of Tomato Shelf Life via Nitric Oxide Treatment Using Air Plasma

“…Therefore, generating appropriate amounts of O3 and NO on-site using plasma technology is more e cient. However, controlling the concentrations of O3 and NO via plasma operating conditions is challenging, because various byproducts, such as NO 2 and NO 3, are also produced [25,26], complicating the utilization of plasma-generated chemicals. Managing such a complex gaseous system is di cult.…”