A green route to nitrate-selective nitrogen fixation: catalyst-free hybrid discharge integrating plasma–liquid energy coupling

Abstract

This study presents a catalyst-free strategy for nitrogen fixation via synergistic needle-water and bubble discharge under ambient conditions. The hybrid design spatially integrates spark and bubble discharges, enabling complementary reactive species generation and enhancing N₂ activation efficiency. Transient spark discharge at the needle-liquid interface produces high-energy electrons and reactive radicals, while bubble discharge facilitates sustained gas-phase excitation and NO_x transport. Mechanistic analysis reveals that the interplay between discharge zones promotes efficient oxidation of NO to NO₂ and subsequent conversion to NO₃⁻ in the aqueous phase. This integrated platform advances plasma-driven nitrogen fixation without catalysts or harsh conditions, offering mechanistic insights and a scalable pathway for sustainable fertilizer production.