Facile Fabrication of Anatase TiO₂ Microspheres on Solid Substrates and Surface Crystal Facet Transformation from {001} to {101}

Abstract

Anatase TiO(2) microspheres with controlled surface morphologies and exposed crystal facets were directly synthesized on metal titanium foil substrates by means of a facile, one-pot hydrothermal method without use of any templating reagent. The obtained products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelecron spectroscopy (XPS), and the focused ion beam (FIB) technique. The sizes of the resultant microspheres ranged from 1.1 to 2.1 μm. The transformation of anatase TiO(2) microspheres with exposed {001} facets surface to nanosheets surface with {101} facets was achieved by simply controlling the hydrothermal reaction time. The anatase TiO(2) microspheres with exposed square-shaped plane {001} facets were obtained by controlling the reaction time at 1 h. The prolonged reaction time transforms the anatase TiO(2) microspheres with exposed square-shaped plane {001} facets to eroded {001} facets then to a nanosheet surface with exposed {101} facets. With hydrothermal synthesis, the surface morphological structure and crystal facets formation are highly dependent on dissolution/deposition processes, which can be strongly influenced by attributes, such as pH of the reaction media, the total concentration of dissolved and suspended titanium species, and the concentration of fluoride in the reaction solution. The changes of these attributes during the hydrothermal process were therefore measured and used to illustrate the morphology and crystal-facet transformation processes of anatase TiO(2) microspheres. The surface morphologies and crystal-facet transformations during hydrothermal processes were found to be governed by the compositional changes of the reaction media, driven by dynamically shifted dissolution/deposition equilibria. The photocatalytic activities of the photoanodes made of anatase TiO(2) microspheres were evaluated. The experimental results demonstrated that the photocatalytic activity of anatase TiO(2) microspheres with exposed {001} facets was found to be 1.5 times higher than that of the anatase TiO(2) microspheres with exposed {101} facets.

Anatase TiO2 mesocrystals with exposed (001) surface for enhanced photocatalytic decomposition capability toward gaseous styrene

“…The corresponding high-resolution TEM image (bottom inset in Fig. 1D) shows the perpendicular lattice spacing of 0.19 nm representing the (2 0 0) and (0 2 0) atomic planes of anatase TiO 2 , further confirming that the exposed crystal facet of the nanocrystal is indeed the {0 0 1} facet [30]. These exposed {0 0 1} faceted surfaces of the nanocrystals constitute a larger (0 0 1) surface dominated anatase TiO 2 crystal.…”

Nb, F-codoped TiO2 hollow spheres with high visible light photocatalytic activity

“…As known [2,14,24], the surface energy and reactivity of the {001} facet are relative higher than those of other facets in the anatase TiO 2 . During the process of TiO 2 crystal growth, fluorine ions in the sol precursor were preferentially adsorbed on the {001} facets, which retarded the growth and facilitated the formation of {001} facets.…”

Enhanced simultaneous PEC eradication of bacteria and antibiotics by facilely fabricated high-activity {001} facets TiO2 mounted onto TiO2 nanotubular photoanode

“…As reported, the anatase-to-rutile phase transformation prefer to occurring at higher temperatures (Jarosz et al, 2015). The eroded {001} facets were due to the HF etching/ dissolution effect at high recalcination temperature (Zhang et al, 2011a). In addition, high recalcination temperature would lead to the break of surface TieF bond and subsequent to the volatilization of F (Liu et al, 2009a).…”

“…1d), the corresponding selected-area electron diffraction (SAED) pattern recorded from the circled area (upper-left inset in Fig. 1d) indicated a best fit to polycrystalline anatase (Zhang et al, 2011a). The corresponding high-resolution TEM (HRTEM) image (lower-left inset in Fig.…”