Chemical reactions occurring at a plasma-liquid interface generally fall into one of two categories: electrolytic reduction-oxidation reactions or the dissolution of gaseous products from the plasma phase. The former is most often observed in direct current (DC) systems, while the latter is typically associated with alternating current (AC) dielectric barrier discharges (DBD). In this work, an argon DC microplasma jet was used as a cathode to electrolyze saline solutions. Electrolytic reduction-oxidation reactions yield sodium hydroxide, while reactions occurring in the plasma phase produce nitric acid and hydrogen peroxide. It is found that the final products in the solution depend heavily on the composition of the ambient background gas in the reactor vessel. With a background gas of oxygen or argon, electrolytic production of sodium hydroxide (NaOH) dominates, while nitric acid (HNO_3) formed by the dissolution of NO_2 dominates in the case of air and nitrogen. For pure nitrogen, the production of nitric acid is limited by the rate at which oxygen is produced from water electrolysis.
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