Tuning Product Distribution in Plasma‐Activated Water by Modifying Reactor Design

The need for sustainable, nitrogen‐bound fertilizers motivates low‐energy unconventional routes. We present a plasma‐activated water approach where nitrogen is bubbled through water, producing reactive nitrogen species that generate products such as nitrate and ammonium. To elucidate how reactor geometries affect product distribution, three geometries were compared: the slurry reactor, where plasma streamers propagate across a stirred liquid containing dispersed catalyst, the needle film reactor, and the needle packed reactor with an inner electrode housed in a submerged quartz tube. We observed that slurry configuration produced a more oxidative environment, reaching 9.58 mg of NO 3 − (99.73% selectivity) and 0.026 mg of NH 4 + at 25 mL/min with no catalyst. Conversely, the needle film configuration shifted the ion distribution toward cationic products, yielding 1.75 mg of NO 3 − (86.44% selectivity) and 0.274 mg of NH 4 + at 25 mL/min, while the needle packed bed reactor hindered the production of both products leading to the lowest yields for both analytes. These results show that reactor design and catalyst integration can tune redox pathways toward sustainable nitrogen fertilizer production.