Figure 2.

TEM images of air-TNTs and H₂-TNTs.

Notes: (A, a) air-TNTs and (B, b) H₂-TNTs. A and B represent the cross section of samples; a and b represent the high resolution of transmission electron microscopy images of A and B. In (b), a short dashed curve is applied to outline a portion of the interface between the crystalline and the disordered outer layer (marked by black arrow).

Abbreviations: TEM, transmission electron microscopy; air-TNTs, air-annealed TiO₂ nanotubes; H₂-TNTs, hydrogenated TiO₂ nanotubes.