CO₂ reforming of CH₄ in single and double dielectric barrier discharge reactors: Comparison of discharge characteristics and product distribution

CO₂ reforming of CH₄ in a non-thermal plasma process (e.g., dielectric barrier discharge, DBD) possesses dual benefits for our environment and energy needs. However, this process is strongly influenced by the dielectric structure of the DBD. Here, plasma CO₂ reforming of CH₄ has been performed in both single-dielectric and double-dielectric DBD (DBD-SD and DBD-DD) reactors under atmospheric pressure. Electrical and optical characterization, along with temperature measurements are performed to understand the influence of the DBD-SD and DBD-DD designs. Reactor performance for reforming is compared under different discharge powers. The results show that CO₂/CH₄ discharges in both DBD-SD and DBD-DD display typical filamentary microdischarges. Compared with the DBD-DD, the DBD-SD reactor exhibits a larger number and higher intensity of current pulses, which leads to a higher electron density and formation of reactive species. The highest conversion of CO₂ (24.1 %) and CH₄ (49.2 %) are achieved in the DBD-SD at a high discharge power (75 W). Moreover, higher selectivities of gaseous products are obtained in the DBD-DD, while the DBD-SD reactor shows a higher selectivity for liquid products, mainly including methanol and acetic acid. The highest energy efficiencies for reactant conversion (0.34 mmol/kJ), gaseous and liquid production formation (0.26 mmol/kJ and 0.015 mmol/kJ) are achieved in the DBD-SD reactor at a low discharge power (22 W), resulting from the low energy loss to the environment. However, the carbon deposited on the inner electrode surface in the DBD-SD would have an adverse influence on the reactor's performance. Further research on the optimization of the DBD reactor to establish an efficient plasma-catalysis system is required for industrial applications.