Speaker
Description
Plasma discharges generated by moderate frequency, low energy pulses in a flowing gas-liquid (argon-water) reactor produce hydrogen peroxide ($H_2O_2$) at moderately high energy yields. The leading hypothesis is that the $H_2O_2$ is generated from the recombination of hydroxyl radicals ($·OH$) which are formed by the plasma electrons reacting with vaporized water. Experiments with carbon monoxide as an $·OH$ scavenger have shown that the primary yield of $·OH$ far exceeds what can be accounted for in $H_2O_2$. Similar to $CO$, $NO$ can also be used as a gas phase $·OH$ scavenger leading to the formation of water soluble $HNO_2$ and $HNO_3$. Gas phase $NO_2$ can also be formed from reaction of $NO$ and atomic oxygen, however because the atomic oxygen must ultimately come from $H_2O$ in the $Ar/NO/H_2O$ mixtures, this provides further insight into both the primary $·OH$ yield and reaction pathways for nitrogen fixation with plasma. The main objective of this work is to utilize $NO/Ar$ mixtures (0-20000 ppm $NO$) to assess both the primary yield of $·OH$ and the roles of $·OH$ and atomic oxygen in the reaction pathways leading to $NO_2^-$ and $NO_3^-$. A continuous gas-liquid film reactor with deionized water is utilized and the liquid phase ($NO_2^-$ and $NO_3^-$) and gas phase ($NO$ and $NO_2$) are analyzed using ion chromatography and FTIR, respectively. A variable nanosecond power supply is utilized to determine the effects of pulse width, frequency, and input voltage on the efficiency of $·OH$ generation. The plasma properties including gas temperature and electron density are also assessed using Optical Emission Spectroscopy. (This work was supported by the National Science Foundation, CBET 1702166 and Florida State University.)
