Enhancing toluene removal in a plasma photocatalytic system through a black TiO₂ photocatalyst

An efficient toluene removal in air using a plasma photocatalytic system (PPS) not only needs favorable surface reactions over photocatalysts under the action of plasma, but also requires the photocatalysts to efficiently absorb light emitted from the discharge for driving the photocatalytic reactions. We report here that the PPS constructed by integrating a black titania (B-TiO₂) photocatalyst with a dielectric barrier discharge (DBD) can effectively remove toluene with above 70% CO₂ selectivity and remarkably reduced the concentration of secondary pollutants of ozone and nitrogen oxides at a specific energy input of 1500 J · l⁻¹, while exhibiting good stability. Photocatalyst characterizations suggest that the B-TiO₂ provides a high concentration of oxygen vacancies for the surface oxidation of toluene in DBD, and efficiently absorbs ultraviolet–visible light emitted from the discharge to induce plasma photocatalytic oxidation of toluene. The presence of B-TiO₂ in the plasma region also results in a high discharge efficiency, facilitating the generation of large numbers of reactive species and thus the oxidation of toluene towards CO₂. The greatly enhanced performance of the PPS integrated with B-TiO₂ in toluene removal offers a promising approach to efficiently remove refractory volatile organic compounds from air at low temperatures. (paper)