Engineering Plasma-Liquid Microdischarge Systems for Direct N₂‑to-NH₃ 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.