Sol–gel synthesis of mesoporous anatase–brookite and anatase– brookite–rutile TiO2 nanoparticles and their photocatalytic properties
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Journal of Colloid and Interface Science
Abstract
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TiO2 photocatalysts with a mixture of different TiO2 crystal polymorphs have customarily been synthesized
hydrothermally at high temperatures using complicated and expensive equipment. In this study
TiO2 nanoparticles with a mixture of TiO2 crystals were synthesized using a modified sol–gel method
at low temperature. In order to form nanoparticles with different polymorphs a series of samples were
obtained at pH 2, 4, 7 and 9. Raw samples were calcined at different temperatures ranging from 200
to 800 C to evaluate the effect of the calcination temperature on the physico-chemical properties of
the samples. XRD results revealed that a mixture of anatase and brookite can be obtained in the as-synthesized
samples and in those calcined up to 800 C depending on the pH used to obtain the final product.
Indeed, a mixture of anatase brookite and rutile; or a sample with only rutile phase can be yielded
through further calcination of the as-prepared samples at temperatures P600 C due to phase transformation.
The photocatalytic performance of the samples with a mixture of anatase–brookite; anatase–
brookite–rutile; and anatase–rutile (Degussa P25 TiO2) was exquisitely investigated in the degradation
of methylene blue solutions. The samples obtained at pH 2 and calcined at 200 C possessed the highest
activity of all due to its superior properties. This study elucidates a facile method suitable for the synthesis
of TiO2 with different mixtures of TiO2 polymorphs with desirable properties for various applications.
Keywords
anatase-brookite TiO2