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

Abstract

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 NH4F by using layered H2Ti3O7 ribbons as the precursor. The precursor H2Ti3O7 ribbons were prepared from H+/Na+ ion-exchanged Na2Ti3O7. The suspension solution of protonated H2Ti3O7 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 H2Ti3O7 ribbons. The transformation from staggered [Ti3O7]2– sheets to hollow square rodlike microtubes contained the formation and recombination of the dispersed octahedral [Ti­(OH)2(OH2)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-TiO2 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-TiO2 (1.27 × 10–2 min–1), pH 7.0-TiO2 (1.11 × 10–2 min–1), pH 5.0-TiO2 (0.83 × 10–2 min–1), P25–TiO2 (0.73 × 10–2 min–1), and the blank sample (0.09 × 10–2 min–1), respectively. Compared with P25–TiO2 and the other anatase TiO2 samples, pH 0.5-TiO2 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.

Highly crystalline anatase TiO2 nanocuboids as an efficient photocatalyst for hydrogen generation

“…26,27 Du et al reported that photocatalytic performance also depends on the exposed facets of TiO 2 . 28,29 The photoactivity of TiO 2 is found to be greatly inuenced by a variety of factors including crystalline phase, specic surface area, crystallinity, photon absorption properties and so on. 1,30 Anatase TiO 2 with higher crystallinity is preferred for photocatalysis, since higher crystallinity would mean fewer defects for the recombination of photogenerated electrons and holes.…”

Photocatalytic Carbon Dioxide Conversion by Structurally and Materially Modified Titanium Dioxide Nanostructures

“…Tetragonal nanorods of anatase crystals consisted of high ratio of lateral (100) facets have been fabricated via immersing alkali titanate nanotubes in basic solution followed with hydrothermal transformation [ 45 ]. In addition, Anatase crystals with elongated truncated tetragonal bipyramids that contains high ratio of (100) facets; enclosed via different types of facets (001), (100) and (101) were fabricated via hydrothermal reaction in aqueous HF solution [ 46 ]. However, still a dilemma to fabricate tetragonal cuboid of anatase crystals enclosed only with (001) and (100) facets.…”

Microflowery, Microspherical, and Fan-Shaped TiO2 Crystals via Hierarchical Self-Assembly of Nanorods with Exposed Specific Crystal Facets and Enhanced Photocatalytic Performance

“…Rounded anatase TiO 2 , rod-like rutile TiO 2 growing along the [001] direction, and plate-like brookite TiO 2 with exposed {111} facets were prepared by hydrothermal treatment of the mixed solution of TiCl 3 and H 2 O 2 with different concentrations under certain pH conditions [21]. Moreover, anatase TiO 2 nanocrystals with exposed {010}, {001}, and {111} facets and rutile TiO 2 nanorods with exposed {110} facets on the lateral surface were also prepared using the layered titanate as the titanium source, which exhibited good photovoltaic performance (5.14%) or superior photocatalytic activity for the degradation of organic rhodamine B (76.0%) and methyl orange (96.5%) molecules [22][23][24].…”