Enhancement of Atmospheric Plasma Decomposition of Toluene Using Porous Dielectric Conformally Coated with Titanium Dioxide by Atomic Layer Deposition

The use of atmospheric pressure plasmas together with catalysts for removal of organic volatile compounds (VOCs) from the atmosphere is an area of current research. Dielectric barrier discharge (DBD) systems are widely used to produce non-thermal atmospheric pressure plasmas. For the most effective use of catalysts, it is necessary to maximize the surface area which is exposed to the contaminant and to the active species from the plasma. In this work, we have used atomic layer deposition (ALD) to deposit titanium dioxide catalytic thin films in porous glass labyrinths. ALD is known to produce effective photocatalytic TiO₂ layers and one of its characteristics is the ability to deposit on the internal surfaces within a complex porous material. The performance of a parallel plate DBD system has been tested for the decomposition of toluene. DBD systems with interelectrode material of (a) uncoated porous glass and (b) TiO₂ coated porous glass have been studied. Porous glass has been used to increase the flow path of the gases and to maximize the surface area of the interelectrode medium. The effects of the thickness of TiO₂ and specific input energy (SIE) on the conversion efficiency of the VOCs to CO₂ and CO were measured. The breakdown products of the decomposition were determined by using FTIR absorption measurements for the exhaust gases. Based on these measurements, the carbon balance was close to 100%. The contribution of catalytic reactions to the decomposition became increasingly dominant as specific input energy was increased. The incorporation of the ALD TiO₂ enabled the complete destruction of toluene at a concentration of 2450 ppm in air with an SIE of 336 J/l.