Temperature-Dependent Kinetics of Ozone Production in Oxygen Discharges

Ozone has been widely used for its disinfection properties ever since its efficient production was made possible by plasma discharges. To-date, many experimental and modeling studies have been—and still are—dedicated to further improve the O3 production efficiency. Early on, it became clear that heat has a detrimental effect. Hence, little attention has been paid to the temperature-dependence of the plasma chemistry. However, with the increased use of O2 as (co-)reactant for plasma-based processes at elevated temperatures, this becomes essential. Therefore, we developed a reaction mechanism to study the temperature-dependence of the O2/O3 (plasma) chemistry. Here, we present the experimental validation of this mechanism and an analysis of the different O3 production trends as a function of gas temperature (300–590 K) and discharge power (5–20 W). Through improving key ozone reactions and electron impact dissociation processes, our mechanism could well-predict all experimentally observed trends. Our analysis revealed the importance of the electronic excited states of O2 and how the temperature-dependence of the plasma-based O3 production is highly dependent on the discharge power. Therefore, we believe that this work can contribute to a better understanding of the underlying physicochemical mechanisms of any O2/O3-containing (plasma) process operating at elevated temperatures. Nevertheless, our work also revealed the need for more accurate and comprehensive data with respect to the production and consumption of the electronic excited states of O2.