Nitrogen Fixation into HNO₃ and HNO₂ by Pulsed High Voltage Discharge

Plasma processing induced by discharge offers a unique way to activate nitrogen molecules. Direct nitrogen fixation into water can be realized through this approach. In this study, air or pure nitrogen gas was used as the major nitrogen source bubbled into the discharge reactor. When a discharge occurred, nitrogen was dissociated to active species to take part in the aqueous chemical process. HNO₃ and HNO₂ were produced. The nitrogen fixation process was influenced distinctly by the presence of hydroxyl radicals. During a discharge of 21 min, HNO₃ was the main product and occupied 95% of the total nitrogen content in water. Its concentration was 1.36 × 10⁻³ mol/L⁻¹ with bubbling air and was 1.53 × 10⁻³ mol L⁻¹ with bubbling nitrogen, while the yield was 2.32 × 10⁻⁸ mol J⁻¹S⁻¹ and 2.06 × 10⁻⁸ mol J⁻¹S⁻¹, respectively.