Mechanisms of reducing energy costs for nitrogen fixation using air-based atmospheric DBD plasmas over water in contact with the electrode

In this study, a plasma-assisted nitrogen fixation (NF) process, using dielectric barrier discharge (DBD) air and N2 plasmas ignited over a water surface is presented. We describe the influential factors on the plasma properties through plasma diagnostics such as electrode spacings, applied voltages, and feedstocks to reduce the energy cost for NF. In order to maximize the energy yield and reduce the energy cost for NF as NO3-, the gas phase NOx emitted through the gas outlet is trapped into water. Plasma diagnostics is performed to explain the underlying mechanisms for NOx formation with a reduced energy cost. The analyzed results suggest that decreasing the electrode gap over water surface can effectively reduce the energy cost for NF, and that this can be attributed to the increased number of distributed microdischarges instead of more intense plasma filaments that dominate at higher gaps. This system offers a promising result in NO3− synthesis, with a selectivity of 98 %, and an energy cost of 20.7 MJ/mol.