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

In this study, an atmospheric‐pressure filamentary dielectric barrier discharge plasma is produced over a deionized (DI) water surface to study the physicochemical mechanisms of plasma–liquid surface interactions for NOx synthesis. The gas‐phase plasma diagnostics are performed using optical emission spectroscopy, Fourier‐transform infrared spectroscopy, and by recording voltage–current curves, and liquid‐phase species are analyzed using ion chromatography and UV−visible spectrophotometer. The investigations indicate that the reaction pathways for reactive oxygen and nitrogen species (H2O2, NO 2 ‐, N O 3 −) formation in DI water depend on different experimental conditions. It is observed that the conversion of nitrites into nitrates is significantly influenced by reactive oxygen species. The energy yield for the total amount of NOx synthesized ranges from 1.3 × 10−4 to 3.4 × 10−3 mol/MJ. A newly developed plasma–liquid configuration using filamentary dielectric barrier discharges shows that the conversion and production mechanism of nitrites into nitrates in the liquid is significantly influenced by reactive oxygen species, that is, O and O3. The conversion mechanism of NO 2 − into NO 3 − in such a nonthermal plasma–liquid system is very appealing for future applications, for example, nitrogen fixation, plasma agriculture, plasma medicine, and so forth.