Numerical investigation of plasma CO₂ hydrogenation in a coaxial dual-layer dielectric barrier discharge at atmospheric pressure

Atmospheric-pressure non-equilibrium plasma is emerging as a promising technology for catalyzing CO₂ hydrogenation into valuable oxygenated chemicals at ambient temperatures, making it a focal point under current dual-carbon policies. This paper presents a 2D fluid model for plasma CO₂ hydrogenation using coaxial dual-layer dielectric barrier discharge at atmospheric pressure. This research investigates streamer discharge characteristics induced by varying feed gas volume ratios, positive and negative nanosecond pulsed excitations, and the presence or absence of dielectric sphere filling. The results indicate that increasing hydrogen content in the feed gas under positive nanosecond pulses enhances electron density, local electric field strength, and electron temperature at the streamer forefront, the streamer propulsion speed is faster, and the streamer morphology becomes more convergent. Moreover, higher hydrogen content facilitates methanol synthesis. When the excitation voltage is a negative nanosecond square wave pulse, the higher electron density, spatial electric field and electron temperature are primarily concentrated on the inner dielectric surface, and the streamer is more dispersed, filling the entire gap, exhibiting discharge characteristics distinctly different from those of the positive pulse streamer.