Page 275 - Multifunctional Photocatalytic Materials for Energy

Multidimensional TiO 2 nanostructured catalysts for sustainable H 2 generation 257

Fig. 11.10 SEM and TEM images of pristine TiO 2 NFs (A and B) and TiO 2 hierarchical
nanostructures (C and D) [197]. SEM image of hybrid nanoflake/nanoparticle hierarchical
structure (E) and the corresponding photocatalytic activity (F) [198]. Cross-sectional SEM
image of the TiO 2 nanobelt arrays from NTAs (G) and the photocatalytic degradation
efficiency of RhB by using TiO 2 nanobelt arrays (H) [199].

Based on the coordinately unsaturated Ti and O atoms on (001) and the large TiOTi
bond angles, the (001) facet possesses the highest surface energy. However, because
it is limited by low stability and is a time-consuming synthesis process, challenges
still exist when preparing exposed (001) facets in TiO 2 nanostructures. Using a tra-
ditional hydrothermal method, Lu's group achieved significant advances in the syn-
thesis of anatase TiO 2 with exposed (001) facet from TiF 4 as the predecessor [194].
Various other efforts have been made to prepare anatase TiO 2 with exposed (001)
facets. Jung's group successfully prepared single-crystal-like anatase TiO 2 NTAs with
exposed and chemically active (001) facets, which relied on an oriented attachment
mechanism in a surfactant-assisted process with PVP and acetic acid. Recently, Zhou
et al. also demonstrated that the light absorption edge of TiO 2 nanobelts changes with