The Influence of Carrier Gas on Nanosecond-Pulsed Plasma Discharge Generated in a Water Film Plasma Reactor

Plasma discharge with liquid water has been widely studied due to its potential application in water treatment and chemical synthesis. Hydrogen peroxide, mainly formed by the recombination of hydroxyl radicals, is the major stable product of the plasma discharge with liquid water. The production rate of hydrogen peroxide is affected by operating conditions such as reactor type and input power1 2. In our previous work3, a nanosecond power supply with adjustable pulse width, input voltage and pulse frequency, was used to investigate how input power influences the hydrogen peroxide production in the water film reactor. In the present study we expand upon the previous work with this nanosecond pulsed plasma discharge by considering the influence of carrier gas (argon and helium) on the plasma properties and the formation of hydrogen peroxide. We hypothesize that the carrier gas influences the plasma properties that in turn affect the hydrogen peroxide production rate. The plasma properties, including electron density, gas temperature, and plasma volume, and the hydrogen peroxide production rate are measured in argon, helium, and argon/helium mixtures. We found that the helium plasma is more diffusive compared with the argon plasma. In addition, the helium plasma has a larger volume and lower electron density and gas temperature. These results may be due to the higher thermal conductivity of helium compared to argon. We also found that by combining helium with argon, thus increasing the thermal conductivity over that of pure argon, the plasma became more diffusive with the increasing percentage of helium in the gas mixture.