Modulating the dry reforming of CH₄ via non-thermal plasma under varied electrical waveforms

Dry reforming of methane (DRM) offers an effective route for converting greenhouse gases into value-added products. In this work, the DRM process was investigated using dielectric barrier discharge (DBD) reactors driven by two different power supplies: a sinusoidal alternating current (AC) and a nanosecond pulsed (ns) power supply. The ns pulsed system delivers higher power across the discharge gap, along with increased electron density and mean electron energy, compared to the AC-driven configuration. At P_t = 30 W, with a gas inlet of CO₂:CH₄:Ar = 5:5:90 and a flow rate of 100 ml/min, the gas gap power of ns-DBD reaches 22.6 W and 20 times the electron density of AC-DBD. It also achieves higher conversion rates and a broader product spectrum, including alkenes and alkynes, which are absent in AC-NTP. Optical emission spectroscopy shows stronger dissociation and excitation of CO₂, CH₄, and Ar in ns-DBD, which further increases with Ar content. Under AC-NTP conditions, the formation of CH and CH₂ radicals is limited, which further restricts the production of alkenes and alkynes. Theoretical analysis indicates that AC-DBD, rich in CO₂ vibrational excitation, promotes acid formation via Eley-Rideal mechanisms, while the high O atom concentration in ns-DBD favors alcohol production.