Page 260 - Multifunctional Photocatalytic Materials for Energy

Multidimensional TiO 2 nanostructured catalysts for sustainable H 2 generation 243

with a mixed Ar and O 2 flow to obtain Au-modified rutile TiO 2 NWs via an oxida-
tion and thermal evaporation method. The as-prepared, high-density, single-crystalline
TiO 2 NWs with a rutile phase were successfully grown on the quartz substrate. It is
believed that the Ti buffer layers restrict the undesirable reactions between Ti and the
substrate, which ensures the formation of TiO 2 NWs by providing additional Ti vapor
to the Au catalyst (Fig. 11.3C and D) [63,77,78].

11.2.2.3 TiO 2 nanorods
TiO 2 NRs can also be obtained through the preceding methods [71,79,80]. Tanemura's
group obtained dense TiO 2 NRs with a 150–200 nm diameter (Fig. 11.4A) and mi-
crometers in length. Anatase TiO 2 NRs were obtained by dipping AAMs into a boiled
TiO 2 sol, followed by drying and heat treatments. The as-fabricated TiO 2 NRs showed
great uniformity and high crystallinity. Crystalline TiO 2 NRs have also been prepared
through oxidation of Ti plates with H 2 O 2 [85–87]. Wu's group reported the preparation
of highly crystalline TiO 2 NRs via direct oxidation of Ti with H 2 O 2 under a low tem-
perature (80°C) (Fig. 11.4B). The size and morphology of the as-prepared TiO 2 NRs
could be well controlled with the assistance of different surfactants [81,82]. In a related
work, Wang et al. reported a new pulsed chemical vapor deposition (CVD) method to
prepare uniform and dense TiO 2 NRs from TiCl 4 and H 2 O with AAM as substrate [84].
Water was pulsed into the chamber at 600°C for 1.5 s with N 2 flowing for 1 min and
then TiCl 4 for 1.5 s for different growth cycles. The as-synthesized TiO 2 NRs possessed

Fig. 11.4 TEM image of an individual anatase TiO 2 NRs (A) [79,80]. FESEM of the surface
TiO 2 NRs on the Ti plate after soaking in the 30 wt.% H 2 O 2 solution at 80°C for 72 h (B)
[81,82]. FE-SEM image of the TiO 2 NRs at different magnification of 30,000 (C) [83]. SEM
images at 30°C tilted view (D) and cross-section view (E) of vertically aligned and densely
packed TiO 2 NRs on sapphire (100) substrate. TiO 2 NRs grown in nanochannels (F) [84].