Fixation of air nitrogen to ammonia and nitrate using cathodic plasma and anodic plasma in the air plasma electrolysis method

Abstract

The fixation of nitrogen (N₂) from the air into ammonia (NH₃) and nitrate (NO₃⁻) is usually conducted using the Haber–Bosch process, which requires the raw material of hydrocarbons for hydrogen (H₂), which has a large amount of energy but produces high CO₂ emissions. An environmentally friendly and energy-saving alternative is the air plasma electrolysis method, which can be used to synthesize NH₃ and NO₃⁻ under ambient conditions. In this study, this method was used to inject air into the plasma zone in a K₂SO₄ electrolyte solution to produce N₂ fixation compounds. The results showed that the use of cathodic plasma promoted the formation of NH₃ but suppressed NO₃⁻ production. The optimal air injection rate was achieved at 0.6 L.min⁻¹ and an electrical power of 452 W, with a total fixed N₂ of 51.66 mmol. The highest formation of NO₃⁻ in cathodic plasma was obtained in 35 min, with a value of 29.92 mmol, and 2.57 mmol NH₃ was achieved at 60 min. The high concentration of H₂ gas, which is a by-product of this process, can contribute to increasing the use of Haber–Bosch green technology in the production of NH₃.