Water dissociation in a radio-frequency electromagnetic field with ex situ electrodes—modelling of discharge initiation

Applying a new experimental design with a capillary glass reactor and plate electrodes outside of the reactor allowed the initiation of discharges in aqueous electrolytes under the influence of a radio-frequency (RF) electromagnetic field.This study focused on the mechanism leading to the initiation of such discharges in the restriction of a glass tube. The light emission correlated with discharges was analysed with optical emission spectroscopy. Electrons with energies between 20 and 45 eV were responsible for the dissociation of water molecules into (excited) OH, H and O radicals. Current–voltage characteristics were measured before and under discharge conditions. Modelling of the experimental setup and simulation of electrical field strength distribution support the hypothesis of the origin of discharges in general and experimental findings such as ring-shaped discharges and a minimum solution conductivity of about 1 S m−1 required for discharge initiation with RF voltages of 2 kV.