Chemical Reactions Induced by Atmospheric Pressure Hydrogen Plasma

K. Tachibana and K. Yasuoka

Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Japan

Abstract- In plasma applications for water treatment, OH radicals and ozone are generated by using plasma to decompose organic compounds and kill bacteria. Reaction processes with OH radicals and ozone involve oxidative reactions. Though some studies on reduction processes induced by plasma have been reported, atmospheric pressure hydrogen plasma has not been used for water treatment. In this paper, atmospheric pressure hydrogen plasma was generated between a high-voltage electrode and a water surface. We investigated the discharge characteristics of the hydrogen plasma using photographs of plasma, voltage and current waveforms, and optical emission spectra. To examine the reductive power of hydrogen plasma, aqueous nitric acid was irradiated by the plasma. In the result, Glow and pulsed streamer discharge were observed in the DC and pulsed discharge of the hydrogen plasma, respectively. The optical emission spectra showed that intensities derived from H atoms in pulsed discharge were higher than in dc discharge. Nitrate ions in water were not reduced by irradiating aqueous nitric acid with hydrogen plasma whereas ammonium ions were generated in water, which indicates that dissolved nitrogen may have transferred into the plasma region and reacted with hydrogen atoms.

Keywords- Hydrogen plasma, chemical reaction, nitrate ion, ammonium ion



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