Pr 3+ Doped Biphasic TiO 2 (rutile-brookite) Nanorod Arrays Grown on Activated Carbon Fibers: Hydrothermal Synthesis and Photocatalytic Properties

Abstract Praseodymium-doped biphasic TiO 2 (rutile-brookite) nanorod arrays (Pr-TiO 2 NRAs) were successfully prepared via a two-step hydrothermal reaction on activated carbon fibers (ACFs) which pre-coated with TiO 2 nanoparticles at first step. The bicrystalline arrays grown on ACFs are primarily constructed by the well-aligned TiO 2 nanorods growing along [0 0 1] direction, which were indicated by the results of SEM and XRD. The nanorods are uniform in diameter and length with about 250 nm and 2.5 μm. The composite photocatalyst with high specific surface area and well-aligned nanostructure are beneficial to enhance the adsorption capacity and even help to suppress electron-hole recombination effectively, which consequently revealed much better (2 times) catalytic performance than that of commercially available P25 TiO 2 on methylene blue(MB) photodegradation. In addition, the existence of praseodymium in TiO 2 gives rise to shift of absorption edge towards long wavelength, which was indicated by the results of UV-vis DRS. Photodegradation results reveal that Pr-doping significantly improves the activity of TiO 2 , which was 20% higher than that of undoped TiO 2 NRAs for the photodegradation of MB in aqueous medium under visible light irradiation. Meanwhile, the doped amount of Pr had a tiny influence on the photocatalytic performance of the composites. In our experiment, 3% Pr-doped molar concentration was proven to be the relatively optimal dopant concentration for the doping of TiO 2 NRAs. Moreover, the photocatalyst grown on ACFs substrates is favorable to reuse and photodegradation rate kept on 76% even after 4 times of reuse.