CO₂ Hydrogenation Using Nonthermal Plasma: Effects of Packed Beds on Plasma Discharge Behavior

Nonthermal plasma-assisted catalysis offers a promising approach to activate strong chemical bonds such as those in CO₂ and transform such stable molecules into value-added products under ambient conditions. Advancement in this field requires building upon understanding of plasma-catalyst interactions that dictate product selectivity, conversion, and energy efficiency. This study aims to systematically assess how different dielectric supports influence plasma discharge behavior and reactor performance during CO₂ hydrogenation in a dielectric barrier discharge reactor. The dielectric constant of the packing material strongly influences discharge behavior and, consequently, catalytic activity. Among the materials examined, Al₂O₃ exhibited the highest CO₂ conversion of 42% at a plasma power of 23 W, whereas CeO₂ yielded the lowest (∼5%) due to the formation of a diffuse discharge, in contrast to localized discharges or surface streamers. CO₂ conversion over CeO₂ beds of a given particle size were nearly identical irrespective of changes in particle size, further supporting this discharge-dependent behavior. Notably, this work highlights the importance of comparing reactor performance for packed beds under nonpartial discharge operation.