Hydrothermal Splitting of Titanate Fibers to Single-Crystalline TiO₂ Nanostructures with Controllable Crystalline Phase, Morphology, Microstructure, and Photocatalytic Activity

Abstract

A simple and efficient inorganic acid-assisted hydrothermal route has been developed for the synthesis of single-crystalline TiO2nanostructures with use of protonic tetratitanate hydrate fibers as a precursor. A variety of TiO2 nanostructures, including aligned nanorods, nanoporous nanostructures, nanocubes, and diamond-shaped nanocrystals, have been prepared with this method. The morphology, crystalline phase, composition, average grain size, band gap, and microstructure of the nanostructures have been determined as a function of the nature and concentration of the inorganic acid (HCl, HNO3, or H2SO4) used for the synthesis. The rutile phase is obtained by using HCl for a concentration range of 0.1−0.4 M and also for 6 M concentration, HNO3 for a concentration range of 0.1−0.2 M and >7 M, and H2SO4 for a narrow concentration range of 0.1−0.9 M. Likewise, the anatase phase is obtained by using both HCl and HNO3 for concentrations of around 0.9 M, and a broader concentration range of 2−7 M with H2SO4. An increase in the band gap of the TiO2 nanostructures from 2.97 to 3.35 eV is observed as the crystalline phase changes from rutile, to a mixture of rutile and anatase, and subsequently to pure anatase. Correspondingly, the photocatalytic activity of the synthesized nanostructured materials is found to be dependent on the crystalline phase, composition, and surface area.

The evolvement of pits and dislocations on TiO2-B nanowires via oriented attachment growth

“…Previous work also reveals that titanate nanowire will be fractionized into small single crystalline grains in more rigorous conditions [13]. Moreover, the growth mechanism of TiO 2 -B film has demonstrated that the (0k0) planes of TiO 2 -B were derived from the a-axis orientation of hydrogen titanate [14].…”

Study on crystallinity and morphology controlling of titania using acrylamide gel method and their photocatalytic properties

“…A higher value of the constant k for a particular catalyst means that it has a higher activity for photodegradation of CR, which allows us to quantitatively determine the photocatalytic activities of the different catalysts [43]. The correlation constants for the fitted lines were calculated to be between 0.99 and 1, which indicates that the photocatalytic degradation of CR can be described by a first-order kinetic model.…”

Synthesis of TiO 2 visible light catalysts with controllable crystalline phase and morphology from Ti-bearing electric arc furnace molten slag

“…It is shown that the photodegradation efficiency of the obtained TiO 2 could increase from 67.62% to 73.00% and 91.00% as R L/S decreased from 100:1 to 75:1 and 50:1, respectively, which may be ascribed to the different crystal phases and specific surface areas of as-synthesized TiO 2 . Larger specific surface area is beneficial to the adsorption of oxygen atoms to form active hydroxyl groups, resulting in enhancement of the photocatalytic activity (Shen et al, 2008). As shown in Fig.…”

“…However, the photocatalytic performance would be improved greatly if the crystalline phase and morphology of the prepared TiO 2 photocatalyst could be controlled, since the properties of TiO 2 photocatalysts are closely related to its crystalline phase and morphology. Up to now, a variety of TiO 2 photocatalysts with different crystalline phases and morphologies have only been synthesized from chemical reagents (Li et al, 2006(Li et al, , 2008Shen et al, 2008;Sun et al, 2011;Zhou et al, 2011). Therefore, synthesis of a TiO 2 photocatalyst with controlled crystalline phase and morphology from Ti-bearing EAF slag under mild treatment conditions will be the focus of this study.…”