CO₂ conversion under Non-Thermal plasmas driven by various power supplies

CO₂ transformation through non-thermal plasma (NTP) provides a promising route for mitigating greenhouse gas emissions and advancing sustainable energy technologies. This study investigates CO₂ decomposition in a coaxial dielectric barrier discharge(DBD) reactor powered by two distinct excitation modes: sinusoidal alternating current(AC) and nanosecond pulsed(ns). Waveform modulation is proposed as an effective strategy to regulate downstream reaction pathways by tailoring CO₂ excitation states. Experimental results demonstrate that the ns-DBD system exhibits higher power deposition (17.2 W), greater electron density (1.04 × 10¹³ cm⁻³), and elevated mean electron energy, leading to superior CO₂ conversion (17.2 %) compared with the AC-DBD system (13.3 %). Optical emission and kinetic analyses reveal that under identical Ar-rich conditions, vibrational excitation predominates in AC-DBD, whereas electronic excitation dominates in ns-DBD. These distinct excitation pathways result in differentiated product distributions and catalytic behaviors. The ns-DBD system generates abundant short-lived reactive species that enhance intermediate conversion and suppress secondary decomposition, thereby improving selectivity and energy efficiency. In contrast, the continuous and mild AC discharge stabilizes high-energy intermediates and enables alternative reaction routes. The findings highlight that waveform selection and gas composition tuning are critical for optimizing plasma-catalytic CO₂ conversion toward desired products such as oxygenates.