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Nanotubed titanic acid (H 2 Ti 2 O 4 (OH) 2 ) was prepared from nanotubed sodium titanate (Na 2 Ti 2 O 4 (OH) 2 ) by an ion exchange reaction in a pH = 1 HCl solution. The effect of annealing temperature on the morphology, structure and photocatalytic behavior of nanotubed H 2 Ti 2 O 4 (OH) 2 was studied by means of TEM, XRD, DTG, DSC, BET and ESR. The results showed that nanotubed H 2 Ti 2 O 4 (OH) 2 is thermally unstable. Its dehydration consists of two steps. In the first-step dehydration, single-electron-trapped oxygen vacancies (SETOVs) were generated. Accompanying the second-step dehydration, the transition of crystal form from orthorhombic system to anatase took place, at the same time the nanotubes broke. At T > 300 • C, when the SETOV concentration greatly increased, the interaction between SETOV happened. (V O o ) x formed could play the role of recombination center of photogenerated e − -h + and make the photocatalytic behavior of TiO 2 (anatase, obtained from 500 • C-treated nanotubed H 2 Ti 2 O 4 (OH) 2 ) to become bad.

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