Plasma-assisted conversion of CO2in 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 (>3.0 eV) 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.