One-Dimensional TiO2 Nanomaterials: Preparation and Catalytic Applications

Abstract

This work reports on the syntheses of one-dimensional (1D) H₂Ti₃O₇ materials (nanotubes, nanowires and their mixtures) by autoclaving anatase titania (Raw-TiO₂) in NaOH-containing ethanol–water solutions, followed by washing with acid solution. The synthesized nanosized materials were characterized using XRD, TEM/HRTEM, BET and TG techniques. The autoclaving temperature (120–180 °C) and ethanol-to-water ratio (V_EtOH/VH₂O = 0/60∼30/30) were shown to be critical to the morphology of H₂Ti₃O₇ product. The obtained H₂Ti₃O₇ nanostructures were calcined at 400–900 °C to prepare 1D-TiO₂ nanomaterials. H₂Ti₃O₇ nanotubes were converted to anatase nanorods while H₂Ti₃O₇ nanowires to TiO₂(B) nanowires after the calcination at 400 °C. The calcination at higher temperatures led to gradual decomposition of the wires to rods and phase transformation from TiO₂(B) to anatase then to rutile. Photocatalytic degradation of methyl orange was conducted to compare the photocatalytic activity of these 1D materials. These 1D materials were used as new support to prepare Au/TiO₂ catalysts for CO oxidation at 0 °C and 1,3-butadiene hydrogenation at 120 °C. For the CO oxidation reaction, Au particles supported on anatase nanorods derived from the H₂Ti₃O₇ nanotubes (Au/W-180-400) were 1.6 times active that in Au/P25-TiO₂, 4 times that in Au/Raw-TiO₂, and 8 times that on TiO₂(B) nanowires derived from the H₂Ti₃O₇ nanotubes (Au/M-180-400). For the hydrogenation of 1,3-butadiene, however, the activity of Au particles in Au/M-180-400 was 3 times higher than those in Au/W-180-400 but similar to those in Au/P25-TiO₂. These results demonstrate that the potential of 1D-TiO₂ nanomaterials in catalysis is versatile.