Colorimetric quantification of aqueous hydrogen peroxide in the DC plasma-liquid system

The quantification of hydrogen peroxide (H₂O₂) generated in the plasma-liquid interactions is of great importance, since the H2O2 species is vital for the applications of the plasma-liquid system. Herein, we report on in situ quantification of the aqueous H₂O₂ (H₂O_2aq) using a colorimetric method for the DC plasma-liquid systems with liquid as either a cathode or an anode. The results show that the H₂O_2aq yield is 8–12 times larger when the liquid acts as a cathode than when the liquid acts as an anode. The conversion rate of the gaseous OH radicals to H₂O_2aq is 4–6 times greater in the former case. However, the concentrations of dissolved OH radicals for both liquid as cathode and anode are of the same order of tens of nM.