Analysis of the production mechanism of H₂O₂ in water treated by helium DC plasma jets

In this paper, helium plasma jets are used for water activation to explore the production mechanism of H₂O₂ in the water. Either positive or negative DC voltage is used for the plasma excitation. It is found that the concentration of aqueous H₂O₂ induced by the positive plasma jet is ∼4 times larger than that by the negative plasma jet with similar average discharge current. Three production pathways of aqueous H₂O₂ are considered important in literature, including the electrolysis, the dissolution of gaseous H₂O₂, and the combination of aqueous OH. However, the first two pathways are found to have similar contributions on H₂O₂ production for the positive and negative plasma jets. It is deduced that the OH combination in the surface layer of the plasma-activated water is most responsible for the concentration difference of aqueous H₂O₂ between the two plasma jets. (paper)