C2H2 oxidation by plasma/TiO2 combination: Influence of the porosity, and photocatalytic mechanisms under plasma exposure

Abstract Plasma/catalyst combination is an active solution to reach high conversion rates at low energetic cost. TiO 2 is one of the catalysts frequently used in dielectric barrier discharges. Plasma/TiO 2 synergy was already exhibited but the mechanisms still have to be understood. This work distinguishes three main effects involved in the synergy: (a) effect of catalyst on the injected power, (b) the effect of porosity on C 2 H 2 oxidation, and (c) the photocatalytic degradation of C 2 H 2 on TiO 2 under plasma exposure. Different glass fibres-based catalytic materials coated with SiO 2 and/or TiO 2 nano-particles are used to separate these three contributions regarding to C 2 H 2 conversion. It is reported that at constant voltage the injected power is mainly increased by the presence of glass fibres. C 2 H 2 oxidation is mainly enhanced by the macroporosity of glass fibres and in a minor way by the nano-particles. The production of O atoms close to the surface is probably responsible for the higher C 2 H 2 removal efficiency with porous material. The photocatalytic activity of TiO 2 is negligible in the plasma except if additional UV lamps are used to activate TiO 2 . With external UV, photocatalytic activity is more efficient in the plasma phase than in a neutral gas phase. This plasma/photocatalysis synergy is due to the use of O atoms in photocatalytic mechanisms.