Surface fluorinated Ce-doped TiO2 nanostructure photocatalyst: A trap and remove strategy to enhance the VOC removal from indoor air environment

A series of cerium-doped TiO2 anatase-brookite polymorphs with different low Ce contents (0.2-1.5 atomic %) were synthesized by a facile hydrothermal method as efficient visible-light-driven photocatalysts. Then, the surface fluorination of the Ce-TiO2 photocatalyst with optimum Ce content (0.5%Ce-TiO2) was studied further to increase its efficiency, particularly in high humid conditions. After coating of the synthesized photocatalysts on nickel foam, their photocatalytic performance was investigated in a continuous-flow reactor with small residence time through methyl ethyl ketone (MEK) degradation. Based on the characterization results, using an appropriate amount of Ce dopant and surface fluorination can significantly inhibit the charge carrier recombination. A significant improvement (about 4 times) in visible-driven photocatalytic activity has been demonstrated for F-0.5%Ce-TiO2 compared to P25. Specifically, the surface fluorination promoted the 0.5%Ce-TiO2 photoactivity in high humid conditions (e.g., 40% and 60%). After surface fluorination, removal efficiency of 0.5%Ce-TiO2 at RH = 60% improved from 52% to 60% under UV and from 47% to 54% under visible light irradiation. The MEK removal efficiency for one-layer and three-layer of 0.5%Ce-TiO2 photocatalyst are respectively 62% and 79% under UV, and 56% and 75% under visible light irradiation. Notably, the by-product generation was considerably decreased and reached the lowest amount for the three-layer F-0.5%Ce-TiO2 photocatalyst.