A Water‐Soluble Titanium Complex for the Selective Synthesis of Nanocrystalline Brookite, Rutile, and Anatase by a Hydrothermal Method

Abstract

A complex pattern: Single‐phase brookite, rutile, and rutile–anatase nanoparticles can be prepared from the new water‐soluble titanium(IV) complex (NH4)6[Ti4(C2H2O3)4(C2H3O3)2(O2)4O2]⋅4 H2O. It appears that the structural similarity of the complex anion to the brookite architecture allows the directional synthesis of brookite nanopowders in a pure form (see scheme).

Application of Water-Soluble Titanium Complexes as Precursors for Synthesis of Titanium-Containing Oxides via Aqueous Solution Processes

“…40 The present authors have reported that the hydrothermal treatment of aqueous solutions containing water-soluble titanium complexes at 200°C for 24 h induced decomposition of the complexes resulting in formation of nanocrystalline TiO 2 , and more importantly that the four polymorphs of TiO 2 (anatase, rutile, brookite type and TiO 2 (mC)) were selectively synthesized by choosing an appropriate titanium complex and by adjusting the pH of the solution. 27,6971 This development allowed us to investigate the photocatalytic properties of different polymorphs of TiO 2 . It has been demonstrated that a pure TiO 2 (brookite type) has higher photocatalytic activity with respect to NO decomposition than those of the widely used TiO 2 (anatase type) photocatalysts with similar specific surface areas.…”

“…The formation of TiO 2 (brookite type) from Tiga was related to the inherent structure of the complex anion and its similarity to the brookite architecture, 27 which is shown in Figure 29. Figure 30 presents a possible scheme for TiO 2 (brookite type) formation from Tiga (complex 12, Figure 14) under hydrothermal conditions.…”

Hydrothermal synthesis of brookite type TiO2 photocatalysts using a water-soluble Ti-complex coordinated by ethylenediaminetetraacetic acid

“…The situation started to change lately after we have proposed a simple synthesis of single phase nanocrystalline brookite by hydrothermal treatment of a new water-soluble titanium complex coordinated by glycolic acid. 7) This complex molecule contains four titanium atoms interconnected through oxygen atoms of the ligands in the pattern similar to the atomic arrangement of brookite. The brookite-like architecture built into the complex molecule allows for the direct preparation of this polymorph during hydrothermal treatment under basic conditions.…”

“…It was found that brookite could exhibit higher photocatalytic activity in terms of NO gas decomposition than that of the commercial TiO2 photocatalyst P25 (Degussa). 7), 8) It was expected that further increase of photocatalytic activity might be achieved by decreasing particles size of brookite. Nevertheless, it turned out that titanium glycolate complex in the basic solutions provided very narrow range of conditions when brookite could be synthesized, and it was extremely difficult to vary size and morphology of nanopowders.…”

Photo-induced hydrophilicity of brookite TiO₂ prepared by hydrothermal conversion from Mg₂TiO₄

“…The hydrothermal temperatures of brookite formation from Ti(SO 4 ) 2 and TiCl 4 were ²250 and ²200°C, respectively. Tomita et al 24) successfully prepared single-phase brookite TiO 2 by hydrothermal treatment of (NH 4 ) 6 Prior to weighing, TGDTA analysis (up to 1000°C, DTA-50, Shimadzu) was conducted on the MgCO 3 (basic) powder to determine the weight-loss during the heating.…”