Transformation of brookite-type TiO2 nanocrystals to rutile: correlation between microstructure and photoactivity

Snejana Bakardjieva; Vaclav Stengl; Lorant Szatmary; Jan Subrt; Jozef Lukac; Nataliya Murafa; Daniel Niznansky; Karel Cizek; Jaromir Jirkovsky; Nadia Petrova

doi:10.1039/B514632A

Transformation of brookite-type TiO₂nanocrystals to rutile: correlation between microstructure and photoactivity†

Snejana Bakardjieva,*^a Vaclav Stengl,^a Lorant Szatmary,^a Jan Subrt,^a Jozef Lukac,^a Nataliya Murafa,^a Daniel Niznansky,^b Karel Cizek,^b Jaromir Jirkovsky^c and Nadia Petrova^d

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* Corresponding authors

^a Institute of Inorganic Chemistry – ASCR, 25068 Rez (n/Prague), Czech Republic
E-mail: snejana@iic.cas.cz

^b Department of Inorganic Chemistry, Faculty of Natural Sciences of Charles University, Albertov 6, 128 43 Prague

^c Heyrovsky Institute of Physical Chemistry – ASCR, Prague, Czech Republic

^d Central Laboratory of Mineralogy and Crystallography – BAS, 1113 Sofia, Bulgaria

Abstract

Nanometric particles of pure brookite TiO₂ were synthesized by modified thermolysis of reactant solutions containing titania powder, HCl, urea and PEG 10000. Unique flower-like brookite agglomerates with an average diameter of ∼400–450 nm composed of single brookite nanocrystals of ∼4–5 nm were obtained at 105 °C. The brookite → rutile transformation has been studied and TiO₂ mixtures with variable amount of anatase, brookite and rutile polymorphs at different temperatures (from 200 to 800 °C) were obtained. High resolution transmission electron microscopy (HRTEM), electron diffraction pattern and BET/BJH analyses were used to characterize the phase assemblages, crystallite size and pore volume of the pure-phase brookite and TiO₂ mixtures. In order to understand the metastable–stable TiO₂ phase transformation X-ray powder diffraction (XRD) was performed. The photoactivity of pure brookite and TiO₂ powders with different compositions of the brookite–anatase–rutile and anatase–rutile polymorphs obtained during the transitions was examined by photocatalyzed degradation of 4-chlorophenols in aqueous solution. The titania sample having the highest catalytic activity was obtained at 500 °C, contained 3.2% brookite, 42.9% anatase and 53.9% rutile and is referred to as TiO[B])/500 .

Journal of Materials Chemistry

Transformation of brookite-type TiO₂nanocrystals to rutile: correlation between microstructure and photoactivity†

Abstract

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Transformation of brookite-type TiO₂ nanocrystals to rutile: correlation between microstructure and photoactivity

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