Reforming of CH4/CO2 into syngas in nanosecond pulsed discharge plasma at atmospheric pressure

In this study, a central-hole cylindrical electrode–needle electrode configuration spark discharge plasma methane dry reformer is developed through the use of a bipolar nanosecond pulse excitation method, which enables the selective modulation of methane dry reforming (DRM) at low power. This approach subsequently facilitates the generation of a plasma source with high conversion and selectivity. A CO selectivity of 61.38% can be achieved with a mere 3.94 W of power. Under the peak pulse voltage of 26 kV, the pulse repetition frequency of 280 Hz, and the CO2:CH4 ratio of 1:3, the conversions of CH4 and CO2 reached 18.50% and 15.54%, respectively, while the H2 selectivity reached 46.96%. In addition, the energy efficiency is up to 1.31 mmol/kJ. Meanwhile, the pulse repetition frequency and the CH4 and CO2 ratio are found to be the critical factors affecting the product distribution in this work. The diagnostic technique of emission spectroscopy is employed to elucidate the types of active species and the interaction processes that ultimately give rise to an ordered change in CO and H2 selectivity. This analysis demonstrates that the CH4 cracking reaction plays a dominant role in the DRM.