Hollow Square RodLike Microtubes Composed of Anatase Nanocuboids with Coexposed {100}, {010}, and {001} Facets for Improved Photocatalytic Performance

[Image: see text] In this study, hollow square rodlike microtubes composed of anatase nanocuboids with coexposed {100}, {010}, and {001} facets were successfully synthesized via a mild hydrothermal treatment method in the presence of NH(4)F by using layered H(2)Ti(3)O(7) ribbons as the precursor. The precursor H(2)Ti(3)O(7) ribbons were prepared from H(+)/Na(+) ion-exchanged Na(2)Ti(3)O(7). The suspension solution of protonated H(2)Ti(3)O(7) ribbons was adjusted to desired pH values (0.5–13.0) prior to hydrothermal treatment. The elongated direction of the microtubes is along the b axis, according to the profile of the H(2)Ti(3)O(7) ribbons. The transformation from staggered [Ti(3)O(7)](2–) sheets to hollow square rodlike microtubes contained the formation and recombination of the dispersed octahedral [Ti(OH)(2)(OH(2))(4)](2+) monomers, the formation and growth of the initial anatase nuclei, and the reassembly of the anatase nanocuboids along the b-axis direction during the continuous hydrothermal process. The degradation rate of pH 0.5-TiO(2) was the highest at 1.66 × 10(–2) min(–1), which was 1.3, 1.5, 2.0, 2.3, and 18.4 folds higher than that of pH 3.0-TiO(2) (1.27 × 10(–2) min(–1)), pH 7.0-TiO(2) (1.11 × 10(–2) min(–1)), pH 5.0-TiO(2) (0.83 × 10(–2) min(–1)), P25–TiO(2) (0.73 × 10(–2) min(–1)), and the blank sample (0.09 × 10(–2) min(–1)), respectively. Compared with P25–TiO(2) and the other anatase TiO(2) samples, pH 0.5-TiO(2) exhibited the best photocatalytic activity, which was mainly attributed to its larger proportion of {010} (or {100}) facets, smaller crystalline size, higher band gap, and larger specific surface area.