Characterization and photocatalytic activity of titanate nanotube using a solvothermal route

Mischcrystal titanate nanotube has been synthesized via a hydrothermal method on controlling the cosolvent solution. SEM, TEM, XRD, EDS, XPS, FT-IR and Brunauer-Emmett-Teller methods were used to characterize the shape and morphology, crystalline structure, sample formation and specific surface area of as-prepared nanotube. The composition of nanotube could be assigned as H₂Ti₂O₅.H₂O and Na₂Ti₃O₇.nH₂O crystal structures. The shape and morphology of nanotube underwent a drastic change with the emergence of rod-like form when the sintered temperature reached 600°C. The XRD patterns also confirmed the transformation accompanying the occurrence of sodium hexatitanates and rutile TiO₂. When the calcination temperature arrived at 800°C, well-crystallized sodium hexatitanates with rod shape took place. The photocatalytic activities of prepared sample and calcined products were evaluated with rate constant by the decomposition of Rhodamine B. The results showed the initial nanotube had the highest specific surface area but without photocatalytic effect. With the sintered temperature reached 400 and 500°C, the calcined products showed positive photocatalytic activities and the rate constants were around three times than that of the precursor though their specific surface areas were not the largest. However, the heat treated samples in 700-900°C expressed negative photocatalytic effects along with the occurrence of nanorods and rutile titanium oxide.