Nanosecond pulsed plasma jets impinging on water for ammonia generation

Carbon-free nitrogen fixation plays an important role for global environmental sustainability, which demands novel approaches with improved nitrogen-use efficiency and allowing end-point fertilizer delivery. The most popular Haber-Bosch process synthesizes ammonia (NH 3 ) from N 2 and H 2 at high pressures and temperatures. This work investigates the feasibility of using a low-temperature, nanosecond pulsed atmospheric-pressure plasma jet (ns-APPJ) impinging on water for ammonia synthesis. By applying 200 ns, 20 kV pulses at 500 Hz to a hollow needle (0.838 mm ID, 1.270 mm OD), while flowing a N 2 gas through the needle at 490-990 sccm, a plasma jet was generated impinging on 1 mL of deionized water in a grounded PMMA cuvette. The gap distance between the needle tip and the water surface was kept at 5 mm. The production of NH 3 was found dependent on the treatment time, applied voltage, and gas flow rate. Up to 0.041 mg/hr of NH 3 production was obtained in our study. Effects of the use of different feeding gases such as dry air and humid air on the efficiency of NH 3 synthesis are also discussed.