Dielectric Barrier Discharge of Moist Nitrogen: A Methodology for Exclusive NO Generation

Chemical transformations of moist nitrogen in dielectric barrier discharge cold plasma into NO, NO
₂
, and NO
₂
^-
in conjunction with the control for exclusive NO generation are reported. Initial gas-phase products NO and NO
₂
were identified and estimated spectrophotometrically at respective absorption λ
_max
taking the set of three closely spaced peaks around 204, 214.5, and 226 nm in case of the former, while at 400 nm for latter. Other products NO
₂
^-
and H
₂
O
₂
were identified and estimated by wet-chemical sampling methods followed by colorimetric analyzes, respectively, at 540 and 350 nm. NO, NO
₂
, and NO
₂
^-
yields increased continuously, with increase in gas residence time inside the plasma zone, applied voltage between two electrodes, and the moisture concentration in the gas stream. Typical G values estimated are: NO, 3.98 × 10
^-3
; total NO
₂
and NO
₂
^-
, 6.30 × 10
^-3
; and H
₂
O
₂
, 2.7 × 10
^-3
μmol · J
^-1
. In the product mixture, employing NO
₂
and NO
₂
^-
absorber solution, 50-750 ppm level NO was obtained as an exclusive product with 0.05-24 kHz ac power supplies.