Indirect Synthesis System for Ammonia from Nitrogen and Water Using Nonthermal Plasma Under Ambient Conditions

The indirect synthesis of NH₃ from N₂ and H₂O through plasma processing is proposed and demonstrated. NH₃ is a promising hydrogen storage material because of its high hydrogen storage density. Mg₃N₂ is a key material for indirect NH₃ synthesis, because the reaction of Mg₃N₂ with water easily generates NH₃ at room temperature. In this paper, therefore, we focus on generating Mg₃N₂ by nitridation of MgO with nonthermal atmospheric-pressure dielectric barrier discharge (DBD) plasma in a N₂ atmosphere. By intermittent DBD nitridation treatment while the reaction device was cooled in a water bath, a maximum Mg₃N₂ generation efficiency of 93 mg/kWh was estimated. Because NH₃ is generated through a simple chemical reaction, our scheme does not cause NH₃ decomposition by plasma, which is one of the greatest concerns associated with plasma synthesis. Contrary to the conventional NH₃ generation process, which emits CO₂ and requires high temperature and pressure, our scheme enables NH₃ synthesis from N₂ and H₂O without CO₂ emissions. This allows for an onsite small-scale NH₃ synthesis system to be realized under mild conditions, which is necessary for a future low-carbon society.