Background The resource utilization of carbon dioxide (CO₂) through hydrogenation is of great significance for mitigating greenhouse gas emissions and producing value-added chemicals, and low-temperature plasma technology, particularly dielectric barrier discharge (DBD), has emerged as a promising route for CO₂ conversion under mild conditions; however, the discharge characteristics and CO₂ hydrogenation performance of DBD reactors strongly depend on the excitation power supply mode and operating parameters, and systematic comparisons between different power supply modes remain insufficient.

Purpose To solve this question, this study systematically investigates the effects of key process parameters on the discharge characteristics and CO₂ conversion performance of a packed-bed coaxial DBD reactor driven by two different excitation sources, so as to provide experimental references for parameter optimization and engineering application of plasma-assisted CO₂ hydrogenation.

Methods In this paper, a packed-bed coaxial DBD reactor was constructed, and a sinusoidal alternating current (AC) pulse power supply and a nanosecond (NS) pulse power supply were employed as excitation sources respectively; the effects of the CO₂/H₂ inlet volume ratio, discharge voltage, and discharge frequency on the discharge characteristics and CO₂ conversion performance of the two DBD systems were systematically examined.

Results The experimental results show that the optimal combination of process parameters is a CO₂/H₂ inlet volume ratio of 1∶1, a discharge frequency of 6.5 kHz, and discharge voltages of 24 kV for the AC-DBD system and 8 kV for the NS-DBD system; the AC-DBD system delivered higher overall discharge energy and exhibited better steady-state discharge performance, achieving a CO₂ conversion rate of 14.17% with an energy efficiency of 8.62% under optimal operating conditions, while the NS-DBD system, in which a transient strong electric field can be established by nanosecond steep-edge pulses with a weak local thermal effect, could effectively promote the CO₂ hydrogenation reaction process, reaching a maximum CO₂ conversion rate of 19.56% with an energy efficiency of 30.79%, and the selectivities of hydrogenation products such as CH₄ and CH₃OH were significantly higher than those of the AC-DBD system.

Conclusions Compared with the AC-DBD system, the NS-DBD system demonstrates superior CO₂ conversion performance, higher energy efficiency, and better selectivity toward hydrogenation products, indicating that nanosecond pulse excitation is more suitable for plasma-assisted CO₂ hydrogenation; this work can provide experimental references for the parameter optimization and engineering application of low-temperature plasma-assisted CO₂ hydrogenation conversion technology.