Article ID Journal Published Year Pages File Type
149048 Chemical Engineering Journal 2013 8 Pages PDF
Abstract

The hydrothermal phase transition of ammonium titanate into TiO2 in aqueous ammonia media was investigated in the presence of F− ions by adding various kinds of electrolytes such as NaCl, NH4Cl, NaF, and NH4F. The phase composition and the morphologies of the products were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). With the assistance of F− ions, pure brookite TiO2 can be hydrothermally prepared with a wide range of Na+ ion concentrations from 0.25 M to 1.5 M in just 24 h, which has obvious advantages over the previous NaCl scheme [1] and [2]. Moreover, photocatalytic degradation of MO shows that both anatase and brookite prepared in the presence of F− ions show superior photocatalytic activities than those prepared in the absence of F− ions. The phase transition mechanism from ammonium titanate into TiO2 was also proposed. Besides the introduction of Na+ ions that benefits the phase transition from titanate to brookite, F− ions are suggested to play two key roles during the hydrothermal process: catalyzing the condensation reaction of TiOH to produce TiOTi linkages by forming TiF and regulating the intercalation and the de-intercalation of Na+ ions by counteracting the electrostatic interaction between the Na+ ions and the titanate layers.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Presence of F− ion affects the phase transition of ammonium titanate into TiO2. ► Pure brookite TiO2 was prepared in a wide Na+ concentration range with F−. ► F− ion catalyzes the condensation reaction of TiOH to produce TiOTi linkage. ► F− regulates the intercalation/de-intercalation of Na+ in the titanate layers. ► TiO2 prepared in the presence of F− showed superior photocatalytic activity.

Related Topics
Physical Sciences and Engineering Chemical Engineering Chemical Engineering (General)
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