Effects of nonthermal plasma jet irradiation on the selective production of H2O2 and NO2− in liquid water

Abstract

We present the effects of the application of a nonthermal plasma jet to a liquid surface on H2O2 and NO2− generation in the liquid. Two distinct plasma irradiation conditions, with plasma contact and with no observable plasma contact with the liquid surface, were precisely compared. When the plasma was made to touch the liquid surface, the H2O2 concentration of the plasma-treated water was much higher than the NO2− concentration. In contrast, when no observable contact of the plasma with the liquid surface occurred, the ratio of the NO2− to H2O2 concentration became over 1 and NO2− became more dominant than H2O2 in the plasma-treated water. Our experiments clearly show that reactive oxygen and nitrogen species can be selectively produced in liquid using appropriate plasma-irradiation conditions of the liquid surface. The ratio of NO2− to H2O2 was controlled within a wide range of 0.02–1.2 simply by changing the plasma-irradiation distance from the liquid surface.