NH₃and HNO_xFormation and Loss in Nitrogen Fixation from Air with Water Vapor by Nonequilibrium Plasma

Abstract

The current global energy crisis indicated that increasing our insight into nonfossil fuel nitrogen fixation pathways for synthetic fertilizer production is more crucial than ever. Nonequilibrium plasma is a good candidate because it can use N2 or air as a N source and water directly as a H source, instead of H2 or fossil fuel (CH4). In this work, we investigate NH3 gas phase formation pathways from humid N2 and especially humid air up to 2.4 mol % H2O (100% relative humidity at 20 °C) by optical emission spectroscopy and Fourier-transform infrared spectroscopy. We demonstrate that the nitrogen fixation capacity is increased when water vapor is added, as this enables HNO2 and NH3 production in both N2 and air. However, we identified a significant loss mechanism for NH3 and HNO2 that occurs in systems where these species are synthesized simultaneously; i.e., downstream from the plasma, HNO2 reacts with NH3 to form NH4NO2, which rapidly decomposes into N2 and H2O. We also discuss approaches to prevent this loss mechanism, as it reduces the effective nitrogen fixation when not properly addressed and therefore should be considered in future works aimed at optimizing plasma-based N2 fixation. In-line removal of HNO2 or direct solvation in liquid are two proposed strategies to suppress this loss mechanism. Indeed, using liquid H2O is beneficial for accumulation of the N2 fixation products. Finally, in humid air, we also produce NH4NO3, from the reaction of HNO3 with NH3, which is of direct interest for fertilizer application.

Plasma‐treated liquids in medicine: Let's get chemical

“…[ 40,41 ] The use of PTW for nitrogen fixation here eliminates the issue of costly transportation and storage of potentially explosive chemicals such as NH 4 NO 3 . [ 41,42 ]…”

“…[40,41] The use of PTW for nitrogen fixation here eliminates the issue of costly transportation and storage of potentially explosive chemicals such as NH 4 NO 3 . [41,42] To summarize, we believe that PTLs in medicine have a great potential-taken with a pinch of salt: if commercial chemicals are cheaper and simpler in a specific clinical environment, but yields the same effects (e.g., pure water, or buffers), the use of plasma to generate PTLs is an unnecessary complication. On the other hand, plasma synthesis of molecules in liquids remains an intriguing topic of research where the dynamics are extremely complex, and there is still a lack of mechanistic understanding of the processes due to the plethora of components potentially involved.…”

Insights on the Mechanism of Surface-Catalyzed Oxidative Nitrogen Fixation Based on Liquid-Phase Bubble Pin-Plate Discharge

“…However, the above methods of using water as an electrode or insulating medium result in an excessively high EC of the electrolyte water and are not suitable for providing a reaction platform for coupling the plasma excitation products to the catalyst. Meanwhile, the design of catalysts is crucial for improving the performance of various NF processes, which contributes to increasing competitiveness compared to H–B. ,,, …”

“…Meanwhile, the design of catalysts is crucial for improving the performance of various NF processes, which contributes to increasing competitiveness compared to H−B. 13,26,28,29 The study of plasma−catalyst coupling requires an understanding of the plasma discharge mechanism and the synergistic mechanism with the catalyst. Currently, relevant studies have been carried out to reveal the chemical mechanism of NO x generation from NTPNF through experiments or simulations.…”

Production rates and destruction frequencies of ammonia in inductively coupled H2O/N2 and H2/N2 plasmas

“…In spite of the hopeful nature as a hydrogen source, the number of publications that investigate the synthesis of ammonia from nitrogen and water vapor using nonequilibrium plasmas is surprisingly small. [10][11][12][13][14][15] In addition, the synthesis rates realized to date are insufficient to consider the industrial use in future. Recently, many researchers have reported the synthesis of ammonia using liquid water and atmospheric-pressure nitrogen discharge.…”