Competition between ammonia and nitrogen oxides during nitrogen fixation using N2 and H2O plasma without catalysis

The global energy crisis highlights the need for sustainable energy solutions. Nitrogen fixation, converting N₂ into valuable products, is gaining attention. In this study, we investigate the effect of water vapor in gas-phase nitrogen fixation via gas–liquid mixed-phase pulsed discharge. Results show that increasing water vapor enhances nitrogen fixation efficiency but introduces a competitive mechanism between NH₄⁺ and NO_x. This study examines the effect of water vapor on nitrogen fixation via pulsed discharge at 20 kV and 10 Hz. When water vapor content reached 100%, NH₄⁺ concentration decreased by 49.2%, while NO₃⁻ concentration increased by 19%. Additionally, raising the liquid temperature from 6 °C to 80 °C reduced NH₄⁺ by 57.6% and increased NO₃⁻ by 54.1%. Spectral diagnostics and radical scavenging experiments confirmed the key role of H and OH radicals in the fixation process. Reaction kinetics analysis further validated the competition between NH₄⁺ and NO_x synthesis. While water as a raw material is critical for green nitrogen fixation, its impact on product distribution must be considered in optimizing future applications.