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Multidimensional TiO 2 nanostructured catalysts for sustainable H 2 generation 245

(A) (B)

20 nm

1 µm 1 µm
(C) (D)

250 µm 2 µm 0.5 µm
Fig. 11.5 SEM images of uniaxially aligned NFs made from TiO 2 /PVP (A) and TiO 2 (B);
the insets of (B) show enlarged SEM image of the hollow TiO 2 NFs. Overview of the TiO 2
nanostructures with inset showing a single fiber (C). SEM of the surface of the wormlike TiO 2
nanostructure (D) [104,105].

hydrochloric acid (pH = 1.8), 13.38 mL 2-propanol, and 0.5 mL hydrofluoric acid
(HF) were put in a Teflon-lined stainless steel autoclave and kept at 180°C for 5.5
to 44 h (Fig. 11.6A and B) [111,114]. Recently, Guan et al. demonstrated a novel
anatase TiO 2 NS composite material through a hydrothermal method [112]. TiO 2 NSs
were prepared through a new shortcut hydrothermal process. Specifically, TiO 2 pow-
− 1
der (0.8 g) was added to an 8 mol L NaOH solution (80 mL) for 12 h with stirring.
The resulting samples were transferred to a Teflon reactor and kept under 130°C for
3 h. The suspension was cooled to ambient temperature and then was washed with
deionized water (DI) three times. Finally, the as-prepared TiO 2 NSs were dispersed
into ethanol and obtained after drying at 80°C for 4 h (Fig. 11.6C). Based on the
hydrothermal method and corresponding characterization via various spectroscopic
and microscopic techniques, Liu and his coworkers synthesized another TiO 2 NSs and
deposited them on multiwall carbon nanotubes to form a nanocomposite—Fig. 11.6D
shows the TEM image [113].

11.2.4 Synthesis of 3D TiO 2 hollow and hierarchical materials
Along with development of 0D–2D TiO 2 nanostructures, in recent years, 3D TiO 2 ma-
terials been widely studied [115–117]. These materials hold great potential for prac-
tical applications. Thus several studies on the different aspects of 3D-titania materials