Nonheating ozone suppression in pulsed air discharges: role of pulse duration and repetition rate

Abstract

Facilitating the separate production of ozone (O-3) and nitrogen oxides (NO (x) ) in air discharges without a thermal process is of most merit in diversifying plasma technology; in particular, it is a primary requirement in certain cold, heat-sensitive plasma applications. Here, we propose a new method of nonheating ozone suppression in air discharges. The present work demonstrates that controlling the plasma chemical kinetics by adjusting the duration (width) and/or repetition frequency of the high-voltage DC pulse is effective in suppressing ozone formation in a surface dielectric barrier discharge in static ambient air. The temporal development of each oxygen- and nitrogen-related species in air discharge is complicated and shows different trends in the time range mu s; relatively long-lived O-3 and NO (x) are strongly governed by the temporal behavior of short-lived reactive species, such as excited N-2(A) and N-2(v). To quantify time-varying O-3 and NO (x) , an in situ UV absorption spectroscopy is applied to our gas-tight plasma reactor, which is operated in air at 21 degrees C. With a fixed frequency at 10 kHz and decreasing pulse duration from 10 mu s to 0.18 mu s, ozone is quenched faster in the plasma reactor, resulting in an irreversible chemical mode transition from an O-3- to NO-rich environment. From a different set of experiment (with a 200 ns pulse duration and a frequency range of 1-10 kHz), we can conclude that the off-pulse period also plays a crucial role in the temporal evolution of O-3 and NO (x) ; the larger the applied driving frequency is, the earlier the ozone-free phenomenon appears over the discharge time. Our findings represent a breakthrough in expanding the usage of air discharges and their application in various fields of interest.