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

Abstract

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.

Multi-Hollow Surface Dielectric Barrier Discharge for Bacterial Biofilm Decontamination

“…The presented value is only estimative and does not reflect the in situ measurement of hydrogen peroxide production. The most probable hydrogen peroxide production is water molecule splitting, OH radical reactions during the plasma activation, and the preservation by effective absorption into the water [ 1 , 2 , 32 ].…”

“…The inactivation of bacteria is dependent on biofilm thickness, the penetration depth of active particles and induced secondary products. Thus, hydrogen peroxide and OH radicals are very important in the process [ 2 , 11 , 37 ]. To test the effect of plasma-activated media compared to water vapor, we exposed the S. aureus biofilm to condensates and physiological solution (control sample).…”

“…The low-temperature plasma (LTP) generated by various dielectric barrier discharges (DBD) at atmospheric pressure is widely investigated to generate reactive species for surface modification and decontamination. The hydroxyl (OH) radical belongs to the essential reactive agents applied for the generation of OH functional groups on the treated surface and hydrogen peroxide (H 2 O 2 ) in plasma products [ 1 , 2 ]. Such products can enhance biocompatibility and nanoparticle immobilization, and clean and decontaminate various surfaces [ 3 , 4 , 5 ].…”

Plasma-assisted agriculture: history, presence, and prospects—a review

“…Furthermore, under humid conditions (e.g. discharge in the presence of water vapour or humid samples), an additional source of UV photons arises owing to the OH radical [227][228][229][230][231]. However, the fluency of photons to which the treated samples may be effectively exposed considerably depends on both discharge and exposure geometries.…”

Recent advances towards aqueous hydrogen peroxide formation in a direct current plasma–liquid system

“…Later, some kind of a modified viewpoint was proposed, that is, the H 2 O 2aq is formed inside the liquid by the recombination of the OH aq generated in situ in the liquid phase by positive ion bombardment [73][74][75][76][77][78] or by ultraviolet (UV) and vacuum ultraviolet photolysis of water [79,80] (Equations ( 4), ( 5)). Several more recent research studies [81][82][83][84] suggested that gaseous H 2 O 2 is formed in the gaseous plasma by the combination of the OH g species and then a gas to liquid transfer of the gaseous H 2 O 2 (H 2 O 2g ) leads to the formation of the H 2 O 2aq (Equations ( 2), ( 6), (7)). Up to date, the exact mechanism of the H 2 O 2aq formation in the DC plasma-liquid system is still in dispute, although the consensus in these proposals is that the OH radicals are the building block of the H 2 O 2aq species.…”