Discharge characteristics and ozone generation during CO2 to CO conversion by dielectric barrier discharge packed with TiO2-coated glass beads

A packed-bed dielectric barrier discharge was used to investigate CO2 to CO conversion under different operating conditions as frequency, CO2/Ar gas mixture composition and gas flow rate, to understand the effects of their variations on current-voltage discharge characteristics, CO2 to CO conversion ratios, CO yields, and ozone production. Using TiO2-coated glass beads has changed the discharge behavior from the glow mode to a combined filamentary and surface discharge mode, making the discharge more diffuse for higher frequencies in the range of 3.6 to 6 kHz. Higher CO2 to CO conversion and CO yield are achieved by lowering both operating frequencies and CO2 concentrations in CO2/Ar gas mixture. For TiO2-coated glass beads packed discharge, increasing discharge frequency from 3.6 to 6 kHz lower CO2 conversion from 11.2% to 2.5%, while increasing CO2 concentrations in CO2/Ar gas mixture from 10 to 40% lowers conversion from 11.2% to 5%. The enhancement of ozone production by the introduction of TiO2-coated glass beads packing material may be related to improvements of conversion ratio from CO2 to CO and CO yield showing their larger values at lower frequencies and lower CO2 percentages in CO2/Ar gas mixture. Using inexpensive and easily synthesized in large quantities catalyst material, realized by TiO2 coating of glass beads in a microwave plasma torch, has permitted to reach DBD operational modes adequate for CO production in moderate concentrations suitable for applications in medicine and agriculture.