Kinetics of processes initiated in a water cathode by the action of a direct current discharge at atmospheric pressure in air: simulation and experiment

Abstract

The kinetics of the formation of hydrogen peroxide, nitrate and nitrite ions and the pH of the solution, which served as the cathode, were studied under the action of a direct current discharge at atmospheric pressure in air. A 0D kinetic model has been developed that describes the reactions occurring in solution. The model includes 28 components, 119 reactions between them, as well as fluxes of particles coming to the surface of the solution from the discharge. The particle fluxes were determined from the 0D model of a discharge in air based on the self-consistent solution of the Boltzmann equation, the equations of vibrational kinetics for the ground states of N2, O2, H2O, NO molecules, and the equations of chemical kinetics. The proposed model is semi-empirical, since it includes not only known experimental kinetic data, but also some assumptions that were made to match the calculation results with experiment. An analysis of the experimental data and calculations by the model showed that the main factors initiating reactions in solution are the bombardment of the surface by a flux of positive ions accelerated in the cathode potential drop and the flux of NO molecules from the discharge. Ion bombardment leads to the formation of hydrogen peroxide, during the decomposition of which OH radicals are formed, the subsequent reactions of which determine the composition of the particles of the solution. The source of nitrogen-containing particles is the flux of NO molecules from the discharge. Data are given on the kinetics of the concentrations of the main particles of the solution and the analysis of the mechanisms of the processes of their formation and decay. The results of calculations of the concentrations of H2O2, NO2 −, NO3 −, and pH agree with the experiment within the limits of the latter’s accuracy.