Nitrogen fixation and H202H2O2 ${{\rm{H}}}_{2}{{\rm{O}}}_{2}$ production by an atmospheric pressure plasma jet operated in He–H20–N2–O2 gas mixtures

Atmospheric pressure plasmas are widely used for nitrogen fixation processes to produce ammonia NH3 or nitrogen oxides NOx, including, for example, nitrite NO2− or nitrate NO3−. Small‐scale atmospheric pressure plasma jets (APPJs) can provide the production of these species on demand at the site of consumption. The species of interest are generated by the plasma and can be dissolved in liquids, for example, to use them. In this work, liquid treatments were performed by an APPJ operated in a He––– gas composition to investigate the influence of the gas composition on the production of hydrogen peroxide , and . A validation of two diagnostics showed that the spectrophotometric approach using ammonium metavanadate was interfered by other species when was added to the system. Thus, electrochemical sensing of was performed. The concentrations of and were measured by commercially available test kits based on the o‐phythalaldehyde method and the Griess reagent, respectively. At low admixtures, the dominant species was with a maximum concentration of 0.9 mM, while became dominant at admixtures of 0.5% and higher with concentrations of up to 1.5 mM. was also present in the system and could be measured at low concentrations of less than 0.2 mM in the liquid. By varying the treatment distance and the gas flow rate, insights into the transport phenomena of the species and their dissolution into the liquid could be gained. Low‐frequency pulsing of the radio frequency (RF) jet led to an accumulating effect on , a reduced production of and a switch from ‐dominated production to ‐dominated production.