Improvement in ammonia production efficiency via collision of fine water droplets with a nitrogen plasma jet

Plasma-based methods enable the one-step production of ammonia from water under ambient temperatures and pressures without CO 2 emissions, making them a crucial technology for achieving a carbon-neutral society. In the present study, ammonia is produced with a novel technique, mist and plasma (MAP), which enhances the energy efficiency of ammonia production by colliding fine water droplets (mist) with a nitrogen plasma jet. The efficiency of MAP is 57.6 mg-NH 3 /MJ, representing 8-36-fold improvement in efficiency compared with conventional in-liquid plasma techniques and interfacial reactions between nitrogen plasma and static bulk water. This performance is high-level reported efficiency for catalyst-free one-step ammonia production using water under ambient conditions. The efficiency depends on the surface area per unit space volume of the mist, nitrogen gas flow rate, and electrical discharge frequency. Further investigation and optimization could enable highly efficient and sustainable ammonia production technology. • Ammonia was produced by colliding water mist and N 2 plasma (MAP). • By MAP, some benefits such as increasing reaction area were achieved. • MAP increased the efficiency by up to 36-fold. • Efficiency varied with various factors, including nitrogen flow rate. • The maximum efficiency was 57.6 mg-NH 3 /MJ.