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

Ammonia (NH3) 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 NH3 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 NH3 in liquid water. NH3 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 N-15(2) to (NH3)-N-15. The formation of the plasma-water interface was critical to the synthesis of NH3. 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.