Photocatalytic Activities of Titanium(IV) Oxide Prepared from Titanium(IV) Sulfate

Abstract

A series of TiO₂ powders was prepared by calcining titanium(N) hydroxide slurry, which was provided by hydrolysis of titanium(N) sulfate, in the temperature range (To) of 170 to 1000°C. The content of anatase (CA) in the TiO₂ powder and the corresponding crystallite size (LA) increased with increasing To up to 700°C (Fig.1). The transition from anatase to rutile occurred at 740-830°C. The BET surface area (S) of the TiO₂ powder was directly proportional to the content of amorphous TiO₂ (CAM) (Fig.2). The residual sulfate ions in the TiO₂ powder decreased linearly with increasing To, disappearing almost completely above 800°C (Fig.4). The amount of hydroxyl groups located on the TiO₂ surface decreased monotonously with increasing To (Fig.6). The To dependence of the photocatalytic activity of Pt (5 wt%)loaded TiO₂ (Fig.9), with reference to the above structural characteristics of the TiO₂, suggested that the anatase, but not the rutile, has a sufficient photocatalytic activity to reduce 11+ and oxidize 2-propanol when loaded with a small amount of platinum black (Pt)(see also Fig.8).
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However, in another reaction system consisting of 2-propanol and silver salts, even the rutile TiO₂ without Pt could effectively photocatalyze the reduction of Ag+ to Ag metal onto the TiO₂ and oxidation of 2-propanol to acetone (Table 1).