Abstract: Amorphous TiO₂ (Am-TiO₂) was prepared via a simple step through hydrolysis. The as-prepared Am-TiO₂ was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible diffuse reflectance spectroscopy, and N₂ adsorption-desorption. Large surface area (216 m²/g) and abundant surface hydroxyl group/chemical adsorbed water were observed on Am-TiO₂. Compared with crystallized TiO₂, the adsorption edge of Am-TiO₂ exhibited a blue shift (from 411 to 378 nm). Rapid photo-sensitized degradation of rhodamine B (RhB) was achieved on Am-TiO₂ under visible light (λ > 420 nm) irradiation. The pseudo-first-order rate constant (k = 0.0325 min^-1) was 6.5 and 5.2 times that of anatase and TiO₂ P25, respectively. Moreover, both the N-deethylation and cleavage of chromophore ring structure of RhB were observed on Am-TiO₂ while only the latter path predominated on crystallized TiO₂. The difference between cleavage of chromophore ring structure and N-deethylation was ascribed to different anchoring groups of RhB on TiO₂ through –COOH and –N⁺Et₂, respectively. Testing in 4 recycle experiments, the degradation rate of RhB did not change significantly, indicating the excellent stability and reusability of the Am-TiO₂ photocatalyst.

Key words: amorphous, titanium dioxide, rhodamine B, photocatalytic, visible light