Highly concentrated toluene decomposition on the dielectric barrier discharge (DBD) plasma-photocatalytic hybrid system with Mn-Ti-incorporated mesoporous silicate photocatalyst (Mn-Ti-MPS)

This study investigates the Mn-Ti-incorporated mesoporous silicate (Mn-Ti-MPS) as a photocatalyst for highly concentrated toluene removal in a plasma-photocatalytic hybrid system. Various Mn-Ti-MPS Ti/Si molar ratio = 1/4, Mn/Ti molar ratio = 0.01/1 (1 mol%), 0.05/1 (5 mol%) and 0.1/1 (10 mol%)] photocatalysts were successfully synthesized using a common hydrothermal method without causing any structural damage. In the X-ray diffraction (XRD) pattern, the main peaks of the TiO₂ anatase structure and MnO did not show. All samples displayed hexagonal specific peaks at 2.5° (d_1 0 0 plane), 4.1° (d_1 1 0 plane) and 4.7° (d_2 0 0 plane). This indicates that the Ti ions and Mn ions were well substituted into the Si ion sites in the framework of MCM-41. Their surface areas decreased compared with that of pure MCM-41, while the hexagonal straight pore size was distributed in a range of 2.5-3.5 nm. In the Mn-Ti-MPS, much more water and toluene molecules were absorbed compared to the Ti-MPS. From the X-ray photoelectron spectroscopy (XPS) result, it was determined that the hydrophilicity of the Mn-Ti-MPS was stronger than that of the Ti-MPS. Photocatalytic decomposition for highly concentrated toluene of 1000 ppm increased in the Mn-Ti-MPS when compared with the Ti-MPS, while toluene decomposition on 5 mol% Mn-Ti-MPS was remarkably enhanced to 80% in the plasma system. The conversion to CO₂, however, did not improve in the case of the plasma-only system. Nonetheless, in the plasma-photocatalytic hybrid system, the conversion to CO₂ for 5 mol% Mn-Ti-MPS reached 43% (in an 800 ppm toluene conversion).