Effect of segmented electrodes in coaxial cylindrical dielectric barrier discharge on plasma characteristics and acetone oxidation

This work describes the discharge characteristics and acetone degradation with plasma under different electric fields based on a coaxial cylindrical dielectric barrier discharge (DBD) device energized by pulsed power. It is found that the segmented electrodes with appropriate spacing in coaxial cylindrical DBD are beneficial to the plasma ionization. In this work, the plasma distribution, discharge thermal effect, ionization of reactive species, and acetone degradation performance in coaxial cylindrical DBD with different segmented electrodes are systematically investigated. The experimental results show that segmented electrodes with a certain distance can cause additional ionization in the non-electrode-covered region between adjacent electrodes, thus enlarging the plasma region compared with a single electrode with equivalent total electrode length. The additional ionization involved the inner volume discharge between the quartz tubes and the outer surface discharge along the surface of the external quartz tube. The spatial distributions of the inner volume discharge and external surface discharge were predominantly governed by the radial and axial components of the inter-electrode electric field, respectively. The external surface discharge exhibited significant suppression when the electrode spacing was < 1.5 mm, and it reached its maximum length at 3 mm spacing. When the electrode distance increased to 7‒9 mm, a weak ionizing region appeared in the middle of the adjacent electrodes, which could be attributed to the gradual attenuation of the radial component with the increasing electrode spacing. A higher thermal effect and better oxidation of acetone to CO_x (CO and CO₂) were achieved with the segmented electrode; the dual-segment configuration (3 mm per electrode) achieved a reactor temperature of 63.4 °C, representing a 10 °C enhancement over comparable single-electrode systems. Similarly, the CO₂ and CO concentration reached 328.8 mg/m³ and 105.7 mg/m³, respectively, in two 3 mm long segmented electrodes, which was an increase of 12.2% and 25.6%, respectively, compared with the single electrode. Notably, considering the equivalent ionization of the inner discharge with different electrodes, the enhanced thermal effects and CO_x conversion efficiency directly correlate with the expanded plasma zone induced by electrode segmentation. This work provides critical insights into optimizing electrode configurations for efficient plasma-assisted volatile organic compound degradation systems.