Dual-template synthesis of mesoporous TiO2 nanotubes with structure enhanced functional photocatalytic performance

Mesoporous TiO2 nanotubes (m-TiO2-NTs) with outstanding photocatalytic performance have been successfully synthesized, for the first time, through a dual-template method. The dual-template method uses multi-walled carbon nanotube (CNT) as a hard template to control the morphology and cetyltrimethylammonium bromide (CTAB) as a soft template to form the mesoporous structure. The resulting m-TiO2-NTs are characterized by Xray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), nitrogen adsorption-desorption and X-ray photoelectron spectroscopy (XPS). Rhodamine B (RhB) and dibutyl phthalate (DBP) are used as model pollutants to evaluate the photocatalytic properties of the new materials. The m-TiO2-NTs possess a multiple channel tubular structure and have higher specific surface area than TiO2 nanoparticles (TiO2-NPs). These features result in significantly superior photo catalytic activity for photodegradation. Specifically, the reaction rate constant for the photodegradation of RhB is 9.8 times greater with m-TiO2-NTs than it is with TiO2-NPs. In the case of DBP, the rate constant is 7.7 times higher. Photocatalytic removal ratios of gaseous acetaldehyde (CH3CHO) and the generation of COx (CO + CO2) were detected to evaluate the decomposition ability of the materials, m-TiO2-NTs showed the best CH3CHO removal efficiency and the highest CO2 selectivity. The active species of photocatalytic process are found to be (OH)-O-center dot. In addition, the m-TiO2-NTs exhibit excellent thermal and photocatalytic stability even after six recycles. This work demonstrates a novel way to fabricate mesoporous TiO2 nanotubes that have multiple channel tubular structure and to apply them in environmental photocatalysis.