Jump to main content
Jump to site search


Formation Mechanism of TiO2 Polymorphs under Hydrothermal Conditions Based on Structure Evolution of [Ti(OH)h(H2O)6-h]4-h Monomers

Abstract

In hydrothermal synthesis of TiO2, [Ti(OH)h(H2O)6-h]4-h (h is hydrolysis ratio) monomers generated by the dissolution of the precursor containing titanium ions, then the monomers formed TiO2 crystal via condensation reaction. In this paper, the formation mechanism was investigated by hydrolysis ratio rather than reaction parameters such as pH value and temperature, and it was proposed that the hydrolysis ratio determines the crystal structure. According to the principle that olation reaction occur prior to oxolation reaction, the detailed nucleation process of TiO2 was derived by [Ti(OH)h(H2O)6-h]4-h monomer with different hydrolysis ratio, and the corresponding relationship between the hydrolysis ratio and the crystal structure was investigated. When hydrolysis ratio is in the intervals of h ≤ 2, 2 < h < 3, 3 ≤ h < 5 and h ≥ 5, the predicted crystal structures of TiO2 are rutile, a mixed crystal (rutile, brookite and anatase), anatase and brookite, respectively. Under hydrothermal condition, the change of temperature leads to the change of ionization of water, which leads to the deviation of hydrolysis ratio. In order to solve this problem, the calculation method of hydrolysis ratio (h) under different hydrothermal conditions was established by introducing the ion-product correction. Meanwhile, hydrolysis ratio changed dynamically by the condensation reaction of [Ti(OH)h(H2O)6-h]4-h monomer during hydrothermal crystallization, and it may shift to the adjacent crystal formation interval, resulting in the formation of corresponding TiO2 in new interval. The crystal structure of TiO2 synthesized at different hydrolysis ratio by hydrothermal method with Ti(OH)4 as the precursor was consistent with the theoretical prediction.

Back to tab navigation

Supplementary files

Publication details

The article was received on 02 Feb 2019, accepted on 10 Apr 2019 and first published on 11 Apr 2019


Article type: Paper
DOI: 10.1039/C9TC00662A
Citation: J. Mater. Chem. C, 2019, Accepted Manuscript

  •   Request permissions

    Formation Mechanism of TiO2 Polymorphs under Hydrothermal Conditions Based on Structure Evolution of [Ti(OH)h(H2O)6-h]4-h Monomers

    J. Zhang, P. Sun, P. Jiang, Z. Guo, W. Liu, Q. Lu and W. Cao, J. Mater. Chem. C, 2019, Accepted Manuscript , DOI: 10.1039/C9TC00662A

Search articles by author

Spotlight

Advertisements