Nanosecond-pulsed discharge plasma splitting of carbon dioxide

This paper reports on the study of repetitive nanosecond-pulsed discharge splitting of carbon dioxide (CO₂) for the production of CO. Gas chromatography is used to analyze the composition of the reformed gas when CO₂ is exposed to high-voltage (15 kV) very short (10 ns) electrical discharges that deposit as much as 0.4 mJ of energy at a rate of 30 kHz. Conversion rate and energy efficiency are obtained while the discharge pressure is varied between 2.4 and 5.1 atm. At the tested conditions, the maximum conversion rate and energy efficiency are found to be 7.3% and 11.5%, respectively. The energy efficiency drops slightly with increased pressure because of the decreased electric field and electron energy per molecule. An energy balance analysis of a set of CO₂ plasma reactions reveals that the dominant dissociation pathway under these conditions passes through the excitation of CO₂ (10.5 eV) followed by autodissociation into CO and O, which are often in excited states.