Characterization of dielectric barrier discharges with water in correlation to productions of OH and H2O2 in gas and liquid phases

Using several types of dielectric barrier discharges, we studied the production mechanisms of H2O2 molecules in gas and liquid phases. Water vapor was supplied by a water bubbler in a gas-feed line or vaporization of water filling a lower electrode well. Densities of OH radicals were measured by optical emission and laser-induced fluorescence spectroscopic methods and correlated with the H2O2 production in gas phase. The energy yield of H2O2 obtained in the gas-phase synthesis with the supply of water vapor through the bubbler was on the 0.1 g kWh(-1) order, while that in the synthesis with liquid electrode was larger than 1 g kWh(-1). We investigated also the transport of OH and H2O2 species from gas phase to liquid phase, using additional supply of H2O2 through the outside bubbler and ethanol as an OH scavenger admixed either in the bubbling water or electrode water. From those results, we conclude that the production of H2O2 mainly proceeds in gas phase and the difference in the yields is attributed to the efficiency of extracting the product out of the discharge region before being decomposed by the repetitive discharge, which depends on the reactor schemes. (C) 2019 The Japan Society of Applied Physics