Selective Synthesis of Either Nitric Acid or Ammonia from Air by Electrolyte Regulation in a Plasma Electrolytic System

Simple electrolyteregulation in a plasma electrolytic systemrealizes the selective synthesis of nitric acid or ammonia from theair. Thesustainable production of nitric acid (HNO3) andammonia (NH3) using renewable energy sources and readilyavailable feedstock under mild conditions is highly desirable as itcan bypass the energy-intensive Ostwald and Haber-Bosch processes.Here, we report a plasma electrolytic system to selectively synthesizeHNO(3) or NH3 from air by an electrolyte-regulationstrategy. The plasma is generated by air-pulsed positive direct current(DC) corona discharge, which occurs in a 2 mm gap between a tip electrodeand the aqueous solution surface under atmospheric pressure. HNO3 was generated in 0.1 M HCl solution with a selectivity of91.75 & PLUSMN; 6.34%. In contrast, nitrite (NO2 (-)) as the main product (92.38 & PLUSMN; 1.17%) is obtained in 0.1 M KOHsolution, which is utilized as the electrolyte in the subsequent electrocatalyticreduction step to further convert NO x (-) (NO3 (-) and NO2 (-)) into NH3 by employing a Cu2O nanowire electrocatalyst. The lowest total energy consumption ofNH(3) synthesis is 3.91 kWh mol(-1) (NH3), lower than that of most previous reports. This electrolyte-regulationstrategy opens avenues for adjustable production of HNO3 and NH3 in an energy-efficient and sustainable way bya plasma electrolytic system.