Kinetic processes of interfacial transport of reactive species across plasma-water interfaces: the effect of temperature

Abstract

This work quantifies, through use of molecular dynamics (MD) simulations, the kinetic rates of physical surface processes occurring at a plasma-water interface. The probabilities of adsorption, absorption, desorption and scattering were computed for O3, N2O, NO2, NO, OH, H2O2, HNO2, HNO3, and N2O5 as they interact with the interface at three water temperatures: 298 K, 323 K, and 348 K. Species are categorised into the short-residence group (O3, N2O, NO2, and NO) and the long-residence group (OH, H2O2, HNO2, HNO3, and N2O5) based on their mean surface residence time. It is reported that the most probable process for the short-residence group is desorption, which limits their characteristic residence time on the interface to less than 100 ps, while the long-residence species experience a mixture of absorption and desorption, with a characteristic residence time exceeding 200 ps for many species in this group. With increasing water temperature, a universal decline in characteristic surface residence time is observed. It is found that the short-residence group experience a reduction in probability of desorption in favour of scattering, whereas the long-residence group experience a reduction in probability of adsorption in favour of absorption and desorption. The data reported in this work facilitated the development of a basic surface kinetic model, which was used to find that tuning the plasma toward the production of HNO3 will result in an increase in the rate of uptake of reactive nitrogen species by a factor of 250%.