Plasma-assisted conversion of CO₂ in a dielectric barrier discharge reactor: Understanding the effect of packing materials

A cylindrical dielectric barrier discharge (DBD) reactor has been developed for the conversion of undiluted CO₂ into CO and O₂ at atmospheric pressure and low temperatures. Both the physical and chemical effects on reaction performance have been investigated for the addition of BaTiO₃ and glass beads into the discharge gap. The presence of these packing materials in the DBD reactor changes the physical characteristics of the discharge and leads to a shift of the discharge mode from a typical filamentary discharge with no packing to a combination of filamentary discharge and surface discharge with packing. Highest CO₂ conversion and energy efficiency are achieved when the BaTiO₃ beads are fully packed into the discharge gap. It is found that adding the BaTiO₃ beads into the plasma system enhances the average electric field and mean electron energy of the CO₂ discharge by a factor of two, which significantly contributes to the enhancement of CO₂ conversion, CO yield, and energy efficiency of the plasma process. In addition, the highly energetic electrons (>3.0eV) generated by the discharge could activate the BaTiO₃ photocatalyst to form electron-hole pairs on its surface, which contributes to the enhanced conversion of CO₂.