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

Abstract

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.

Graphical abstract