The reaction of NO in a streamer corona plasma is studied systematical
ly as a function of the composition of the gas mixture, the initial co
ncentration of NO, and the discharge repetition rate. The experimental
results show that the reactions of NO depend strongly on the composit
ion of the gas mixture. Reduction is observed in the absence of oxidan
ts such as oxygen and water, but at very high energy cost (>200 eV/NO)
. In the presence of both these oxidants, more than 90% of the NO conv
ersion is oxidation. The lowest energy costs, 24 eV/NO for He mixtures
and 45 eV/NO for N-2 mixtures, are obtained at water and oxygen conce
ntration above 3% and at low discharge repetition rates (<10 Hz). Chem
ical kinetics calculations of the production of radicals in the plasma
show a good agreement with the value derived from the experiments.