Biologically Active NOx Production By Nano-Second Pin-Plate Discharge In Air

Abstract

Atmospheric pressure air plasma discharges can generate abundance of biologically actives such as nitrogen oxides NO_x (NO, NO₂ etc) which are known as very important reactive oxygen and nitrogen species (RONS) in biomedical applications.[1-2] In this work, we focus on the study of NO_x synthesis by nanosecond pin-plate discharge in atmospheric pressure air. The fourier transform infrared (FTIR) spectrum shows the primary species produced by this discharge only include NO_, NO₂, and HONO. The energy costs of NO_x production decrease with increasing pulse width (in the range of 100ns to 260ns) from ~2400 GJ/tN (gigajoules per metric ton) to ~1000 GJ/tN. Detailed investigation of power consumption and NO_x production throughout the pulse gives hints regarding the mechanisms of efficient NO_x synthesis, namely that the initial and inefficient breakdown process is the main sink of energy. We show late-pulse, 2 mm gap NO_x production energy cost may be as low as ~ 300 GJ/tN（~1.4 x 10¹⁷ molecules/J）which is something similar with gliding arc discharge results [3]. A simple 0D post-discharge kinetic model is able to reproduce the experimentally observed trends, assuming the main driver for NO_x production is electronically excited nitrogen species N2,e*. The model implies an initial increasing trend for efficiency with increased N2,e* concentration which may explain the increase in efficiency we observe with increasing pulse width.