<i>In Situ</i> Synthesis and Measurement of Ammonia from Nitrogen by Nanoelectrospray-Based Corona Discharge Coupled with Mass Spectrometry

Ammonia (NH 3 ) is one of the most widely used materials in the chemical industry. Here, we report a proof-of-concept study on in situ synthesis and measurement of NH 3 from nitrogen by nanoelectrospray-based corona discharge coupled with mass spectrometry. The reactions and analytical confirmations were achieved via polarity-reversing nanoelectrospray ionization (PR-nESI). Plasma was generated by corona discharge at the capillary tip during the negative-polarity half cycle. N 2 was fixed through interfacial reactions and transformed to NH 3 in liquid water. NH 3 was accumulated within the aqueous solution in the capillary tip. The solution was sprayed out for analytical confirmation during the positive-polarity half cycle. Isotopic labeling confirmed direct conversion of 15 N 2 to 15 NH 3 . The formation of the plasma–water interface was critical to the synthesis of NH 3 . The addition of a surfactant to the solution could impede the reactions by forming a film at the surface and preventing direct contact between plasma and water.