Formation of highly crystallized TiO2(B) and its photocatalytic behavior

Highly crystallized TiO2(B) in a flat-whiskered morphology, with a width of ∼300 nm, thickness of 50–100 nm, and length of several microns, was successfully synthesized by three-step reactions employing Degussa P25 and CsCO3 as starting materials. The synthesized TiO2(B) with a crystallite size of 30.2 nm demonstrated an extended thermal stability up to 650 °C and an unexpectedly high photocatalytic activity in decomposing 4-chlorophenol (4-CP), and several other organic compounds in aqueous solution. The photocatalytic activity of TiO2(B) heat-treated at 600 °C was 1.26–1.43 and 1.95–2.32 times, respectively, compared to that of Degussa P25 and 25 nm-sized anatase nanoparticle. Kinetic parameters in decomposing dilute 4-CP were also determined by applying the Langmuir–Hinshelwood equation. The equilibrium binding constant (K) of the prepared TiO2(B) was 1.6 times that of Degussa P25, even though its surface area was less than a third, whereas the reaction rate constants (k) were similar. Exceptionally high K is attributable to the unique crystallographic structure of TiO2(B) constructed by stacking of the negatively charged titania blocks, which enhances the adsorption affinity toward organic compounds.