Template-free synthesis of novel TiO2 microtube (MT) and N-doped MT and their photocatalytic properties decomposing organic compounds

Novel TiO2 microtubes (MTs) with a pore size of ∼1.6 µm, a wall thickness of ∼200 nm, and lengths of 15–30 µm were synthesized by solvothermal reaction without templates. TiO2 MTs, self-assembled with highly crystallized anatase particles, were obtained at the specific concentration ranges of titanium tetraisopropoxide (TTIP) and tetrabutyl ammonium hydroxide (TBAH) (0.32–0.45 M TTIP and 0.32–0.38 M TBAH). We also prepared nitrogen-doped TiO2 (N-TiO2) MTs by flowing gaseous ammonia to the bare TiO2 MTs at 550 °C and analyzed the photocatalytic properties of TiO2 MT and N-TiO2 MT in decomposing gaseous isopropanol (IPA) and aqueous salicylic acid (SA). Under UV–visible light illumination TiO2 MT showed slightly lower photocatalytic activities than commercial TiO2 NP (Aeroxide P25), but under visible light N-TiO2 MT demonstrated 2.2–3.4 times higher activities than N-TiO2 NP, presumably due to its effective structure for space-charge separation of the photogenerated electron/hole pairs.