Characterization of Bi/TiO₂ nanometer sized particle synthesized by solvothermal method and CH₃CHO decomposition in a plasma-photocatalytic system

This study focuses on the relationship between the plasma-photocatalytic activity for CH₃CHO (acetaldehyde) decomposition and the surface properties of pure TiO₂ and 10.0 mol% Bi/TiO₂ nano-sized. The TiO₂ and Bi/TiO₂ particles, which were synthesized through the solvothermal method, exhibited a uniformly spherical anatase structure with particle size below 25 nm. The surface area was large (310 m²/g) as compared with that of pure TiO₂ (140 m²/g). Bi/TiO₂ adsorbed a smaller amount of water than pure TiO₂. From the H₂-TPR result, it was identified that Ti³⁺ could be easily transferred into Ti⁰, which affected the photoreaction, over Bi/TiO₂ compared with pure TiO₂. Based on these results, without H₂O addition, acetaldehyde decomposition was higher on Bi/TiO₂ (80% after 40 min). In particular, the by-product (mainly CH₃COOH), a serious problem in the plasma system, was very small in Bi/TiO₂ (below 5.0%) compared with that in pure TiO₂, which was above 20.0%. However, the acetaldehyde removal slightly increased over Bi/TiO₂ with H₂O addition, while it remarkably enhanced over pure TiO₂. This result means that H₂O addition did not have a good influence on acetaldehyde removal over the Bi/TiO₂ with hydrophobic property. However, it did exert a better influence on pure TiO₂ with hydrophilic property.