title: Facet-controlled anatase TiO2 nanoparticles through various fluorine sources for superior photocatalytic activity.
abstract: Reactive surface-exposed anatase TiO2 (a-TiO2) is highly desirable for applications requiring superior photocatalytic activity. In order to obtain a favorable surface, morphology control of the a-TiO2 using capping agents has been widely investigated. Herein, we systematically study the effects of different F sources (HF, TiF4, and NH4F) as the capping agent on the morphology control and photocatalytic activities of a-TiO2 in a hydrothermal process. When either HF or TiF4 was added, large truncated bipyramids formed with the photocatalytically active {001} facet, whereas the NH4F was not effective for facet control, yielding nanospheres similar to the pure a-TiO2. The morphology changes were related to the decomposition behaviors of the F sources in the solvent material: HF and TiF4 decomposed and supplied F(-) ions before a-TiO2 nucleation, which changed the nucleation rate and growth direction, leading to the resultant a-TiO2 morphology. On the other hand, NH4F supplied F(-) ions after a-TiO2 nucleation and could not change the growth behavior. In terms of the photocatalytic effect, the HF- and TiF4-treated a-TiO2 effectively decomposed ∼90% and ∼80% of methylene blue, respectively, in 1 h, while ∼60% was decomposed for the NH4F-treated a-TiO2. Note that pure a-TiO2 photocatalytically decomposed only ∼10% of methylene blue over the same time. These results pave the way to precise control of the facet of TiO2 through using different capping agents.
authors: School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi 440-746, Korea.
authors: Seung Muk
authors: SM
authors: Lee
authors: Geun Chul
authors: GC
authors: Park
authors: Tae Yang
authors: TY
authors: Seo
authors: Seung-Boo
authors: SB
authors: Jung
authors: Ju Ha
authors: JH
authors: Lee
authors: Young Dok
authors: YD
authors: Kim
authors: Dae Hyuk
authors: DH
authors: Choi
authors: Jun Hyung
authors: JH
authors: Lim
authors: Jinho
authors: J
authors: Joo