Abstract
TiO2 (rutile) samples with a hierarchical 3D nanostructure of the particles were synthesized by two methods: liquid hydrolysis of TiCl4 at 90 °С and atmospheric pressure; hydrothermal synthesis from TiCl4 at 160 °С and different [H2O]/[Ti] ratios. The effect exerted by conditions of the synthesis and post-treatments on the crystallite size, morphology, electronic properties and pore structure of the rutile samples was investigated. It was shown that severe hydrothermal conditions with the ratio [H2O]/[Ti] = 20 provide the formation of a more perfect crystal structure of rutile with a smaller band gap energy (3.00 eV against 3.06 eV for the rutile obtained by liquid hydrolysis at atmospheric pressure). The study revealed the stabilizing effect of cerium cations on the pore structure of rutile, which changes upon thermal treatment.
Highlights
Different morphological types of hierarchical 3D nanostructures (HNSs) form a new class of materials for various applications
When TiO2 is exposed to light having photon energy exceeding the band gap, hν>energy band gap (Eg), electrons are excited from valence band (VB) to conduction band (CB), leaving electron vacancies in VB [6,7,8]
XRD, BET, Transmission electron microscopy (TEM) and UV-Vis DR methods were used for comparative analysis of physicochemical properties of TiO2 having a hierarchical 3D structure, which was synthesized at 90 °С and atmospheric pressure or under the conditions of hydrothermal synthesis at 160 °С
Summary
Different morphological types of hierarchical 3D nanostructures (HNSs) form a new class of materials for various applications. The study of TiO2 HNSs has been a hot topic in the field of photocatalysis and photocatalytic materials for energy and environmental applications [1,2,3,4]. The prospects of TiO2 HNSs for the photocatalytic processes are related to the combination of TiO2 benefits including non-toxicity, chemical stability, and electronic configuration with a hierarchical structure, which provides an extended and accessible surface. The photogenerated electrons and holes can migrate to the TiO2 surface and participate in surface redox reactions. The high redox potential of generated holes and the formation of reactive oxidants, resulting from the interaction of generated electrons with surface oxygen, provide an effective degradation of various organic pollutants absorbed on the TiO2 surface [9, 10]
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