Page 266 - Multifunctional Photocatalytic Materials for Energy

Multidimensional TiO 2 nanostructured catalysts for sustainable H 2 generation 249

Fig. 11.7 SEM image of top views of nanoparticulate films deposited by electrostatic
layer-by-layer (ELBL) technique from two different types of TiO 2 NPs (A) [126]; surface of
TiO 2 aerogel film (B) [127]; porous films prepared via photopolymerization-induced phase
separation (PIPS) process from solutions containing Ti(OC 3 H 7 ) 4 (C) [128]; and spray-dried
particles produced from TiO 2 sols with added salt (D) [129]. An individual single microsphere
showing detailed texture and porosity (c. 1 μm in diameter) (E) [130]. SEM image of the
flowerlike TiO 2 spheres obtained by calcination at 500°C for 2 h of the layered protonated
titanate hierarchical microspheres synthesized in solvothermal reaction in the presence of
hexamethy-lenetetramine (F) [131]; and porous TiO 2 NPs prepared with precursor solutions
consisting of brookite NPs with solutions containing 1:2 brookite to 200 nm PSL particles
(G) [132,133]. The platelets formed shells on the solid cores, creating a core-shell structure
after reaction for 24 h. The cores shrank with time, forming a sphere-in-sphere structure
with continuously reducing inner sphere size (H) [134]. SEM image of the hollow TiO 2
microspheres (I) [135].

11.2.4.2 Porous/hierarchical hollow TiO 2 spheres

Spherical morphology of porous or hierarchical hollow TiO 2 materials has been
demonstrated to be beneficial for various applications, including electrochemical en-
ergy storage, photocatalysis, chromatography, and so on. Spherical morphologies of
3D TiO 2 materials adopt various types of architectures, for example, spherical particle