Engineering Plasma–Liquid Microdischarge Systems for Direct N 2 -to-NH 3 Conversion at Ambient Conditions

Ammonia (NH3) can be synthesized directly from N2 and H2O using plasma micro-discharges formed at the water–electrode interface, offering a promising alternative to both conventional electrocatalysis and nonthermal plasma processes. However, discharge performance and stability are strongly affected by device engineering. This study reports the development and engineering of a hybrid electrochemical device that integrates a micro-plasma cathode for sustainable NH3 production under ambient temperature and pressure. Solvated electrons generated through plasma–liquid interactions, particularly within interfacial aerosol microdroplets, act as highly reducing species, eliminating the need for catalysts or external chemical reagents. The effects of the plasma–liquid gap, gas feed flow rate, discharge current, and cathode inner diameter on NH3 yield are systematically investigated. Optimizing these factors enables Faradaic efficiency exceeding 70% and significantly enhances the instantaneous N2-to-NH3 yield, outperforming previously reported plasma–liquid systems. These findings highlight the importance of system engineering optimization for advancing sustainable plasma-assisted nitrogen fixation and for progressing toward industrial scale-up.