Effects of Process Conditions on Gas and Liquid-Phase Fixed Nitrogen Product Distributions in a Plasma Electrolytic Reactor

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🔬研究者:Provides mechanistic insights into plasma-liquid nitrogen fixation, useful for optimizing reactor design and product selectivity.

The fixation of nitrogen is critical to our most basic need, the growth of plants for food. Industrially, the fixation of nitrogen is carried out predominantly via the Haber-Bosch and Ostwald processes which require large, centralized operations and incur significant carbon emissions, thereby posing challenges to both supply-chain resilience and environmental sustainability. Thus, the development of alternative nitrogen fixation methods that are sustainable and deployable at a small scale has emerged as one of our critical technological challenges. Among the different approaches being explored, plasmas in contact with liquids have shown great promise, capable of reacting nitrogen and oxygen in air with water as a source of hydrogen at atmospheric pressure and near room temperature. However, plasma-liquid reactors produce a variety of nitrogen products including ammonium ions (NH 4 + ), nitrate ions (NO 3 - ), and nitrite ions (NO 2 - ), as well hydrogen peroxide, and the complex multiphase, non-equilibrium chemistry is not well understood and thus, difficult to control. In this study, we utilized in-line FTIR gas analysis and conventional liquid-phase detection methods, including colorimetric assays and ion chromatography, to provide insight into the mechanisms behind the different products and influence of various process variables. Two primary setups were examined: a dry pin-to-plate plasma reactor and a plasma electrolytic reactor containing a static electrolyte. In both configurations, we systematically varied process conditions such as gas feed composition (O₂/N₂ ratio), discharge polarity, and time. The dry configuration specifically provided a baseline of gaseous NO and NO 2 species generated at a given current, and we found that the O₂/N₂ ratio is a critical factor in varying the ratio and amount of NO and NO 2 produced. For the electrolytic configuration, additional factors including electrolyte pH and volume were explored to determine their influence on the production of gaseous and liquid-phase nitrogen products. In particular, we found that electrolyte pH is a key parameter which dictates the trapping efficiency, or ratio of gaseous to liquid-phase products, of these reactors. To further understand the capture and retention of reactive nitrogen species, we incorporated a fritted trap with differing electrolytes downstream of both configurations to quantify overall trapping efficiency of gaseous products which would otherwise be lost to the exhaust of the reactor. Complementary control experiments using reference NO and NO₂ gases provided a benchmark for understanding how electrolyte conditions affect the capture and conversion of plasma-generated NO and NO 2 . Together, these results reveal possible reaction mechanisms and the role of the plasma, liquid, and interface for the generation of difference fixed nitrogen species.

• semanticscholar https://doi.org/10.1149/ma2026-01241313mtgabsfirst seen 2026-07-20 05:15:34