Influence of NH3/Ar plasma irradiation on physical and photocatalytic properties of TiO2 nanopowder

NH3(10%)/Ar plasmas were generated at different gas pressures in a mechanical milling chamber, and were uniformly irradiated on an anatase TiO2 powder with 300 m2/g of which corresponding diameter was 7 nm. Crystal structures of the plasma irradiated powders were the same as that of the raw powder, regardless of the gas pressure. On the other hand, the optical property of the resultant powders was varied with regard to the gas pressure. When plasma generated and irradiated at 300 Pa, the powder had the specific surface area (SSA) of 283 m2/g and noticeable absorption in vis light range was observed. In addition, the powder showed an improvement of the photocatalytic oxidation activity of CH3CHO under vis light. These results indicated that the present plasma treatment is capable of modifying TiO2 nanopowder for improving photoactivity without large SSA reduction, which is often seen in the modification with annealing.