Nitrogen Fixation Into Water by Pulsed High-Voltage Discharge

Nitrogen in the bubbling gas was directly fixed into water by pulsed high-voltage discharge. When the discharge occurred, nitrogen could be dissociated to form active N species to take part in the aqueous chemical process. Nitrous acid (HNO₂) was primarily produced, which was further converted into nitric acid (HNO₃). With the formation of HNO₂ and HNO₃, the pH of the liquid decreased. The decrease in pH sped up the conversion from HNO₂ into HNO₃, thus resulted in an increase in the NO₂ ^- concentration at first and a decrease after a turning point. The nitrogen fixation rate with bubbling nitrogen was faster than that with bubbling air in distilled water. By discharge for about 30 min, HNO₂ was converted into HNO₃ as the final products. Its concentrations were 1.96 mmol . L^-1 with bubbling air and 2.34 mmol . L^-1 with bubbling pure nitrogen. The energy efficiencies were 2.08 times 10^-9 and 2.48 times 10^-9 mol . J^-1, respectively.