Non-Thermal Plasma Conversion of Humidified CO₂ into Syngas in a Dielectric Barrier Discharge Reactor: Tuning H2/CO ratios via specific energy input and gas flow rate

This study investigates the non-thermal plasma (NTP)-driven conversion of humidified CO₂ into syngas (H₂:CO:CO2) using a dielectric barrier discharge (DBD) reactor. NTP enables CO₂ and H₂O dissociation at near-ambient conditions through high-energy electron collisions, eliminating the need for thermal input or expensive catalysts. While prior studies have examined gas composition and humidity effects, the influence of specific energy input (SEI) on syngas yield and energy efficiency remains underexplored. Here, we systematically evaluate the relationship between SEI, flow rate, and H2/CO composition. Experiments conducted in a coaxial DBD reactor demonstrate syngas generation with tunable H₂/CO ratios ranging from 0.109 to 0.157. Results indicate that higher flow rates enhance energy efficiency, while increasing SEI leads to a plateau in CO and H₂ production, suggesting limits in ionization efficiency. Overall, these findings can inform the design of next-generation NTP systems towards a circular carbon economy.