From AC to Nanosecond Pulses: Impact of Pulse Duration on Methane Non-oxidative Conversion in a DBD

Today, most hydrogen production is associated with significant greenhouse gas emissions. Given hydrogen’s growing importance across various sectors (mainly fertilizer synthesis, steel production and transportation), there is increasing interest in alternative, low-emission production routes. One promising route is conversion of methane under non-oxidative conditions, which yields hydrogen and carbonated byproducts. In this work, we investigate methane conversion using non-thermal plasma, specifically dielectric barrier discharges. The investigation focuses on the influence of different high voltage signal durations, ranging from milliseconds pulses (pulsed AC, burst mode) to microsecond (µSP) and nanosecond pulses (NSP), on the energy cost (EC). To ensure a valid comparison between modes, a similar specific energy input (5–11 kJ L− 1) is used across different experiments, which are all performed in the same reactor. Results indicate that µSP and NSP present a lower EC (4200–5000 kJ mol− 1) for methane conversion than the burst mode (6000–7000 kJ mol− 1). The burst mode showed no clear improvement compared to AC operation under the explored SEI range. Rotational temperature (Trot) measurements reveal that discharge temperature was higher in the case of the NSP (700–1000 K) compared to the burst mode (500–650 K). Trot for the NSP was correlated with pulse power rather than total dissipated energy, showing that tuning a NSP can effectively control the discharge temperature.