photocurrent response was observed for each switch-on/off event in the case of
graphene–TiO 2 NPs, which confirmed high photoactivity of graphene–TiO 2 NPs
under visible light irradiation. Additionally, our recent research work demonstrated
that the P25/graphene composite could produce the electrons and exhibit a high
photocurrent response under the simulated solar light irradiation (Fig. 5.10d) [48].
5.2.2 Three-Dimensional TiO 2 /Graphene Composite
In addition to 2D-structured composites, the 3D-structured TiO 2 /graphene composites also attracted intense attention in recent years. Compared to the 2D-structured
graphene, 3D graphene such as hydrogel or aerogel has some unique properties. For
example, it has an ultra-low density, three-dimensional network structure, controllable morphology, controllable mechanical strength, excellent electrical conductivity, and strong adsorption for the gasoline and other organic compounds [61–63].
The unique and outstanding performance of 3D graphene mentioned above
determines that the composite of semiconductors compounded with the 3D graphene
has a broad application prospect in the field of environment protection and energy
storage. For photocatalysis application, the TiO 2 -based materials are still the predominant photocatalysts owing to fruitful achievements realized by so many
researchers. Thus, in this section, we also would like to give a simple summarization
of the 3D-structured TiO 2 /graphene composites and applications in photocatalysis.
5.2.2.1 Preparations
Generally, there are three synthesized methods including the evaporation-induced
self-assembly, hydrothermal–freeze-drying, and thermal reduction for the preparation of TiO 2 /graphene hydrogen or aerogel.
The hydrothermal technology is still the main preparation method for the synthesis of 3D-structured TiO 2 /graphene composites. Different from the preparation of
2D-structured TiO 2 /graphene by the hydrothermal method, the freeze-drying after
treatment plays an important role in the establishment of 3D network structure
during the hydrothermal process. A room-temperature or high-temperature drying
will destroy the skeleton of 3D graphene, resulting in the failure of the formation of
aerogel or hydrogel. Wan et al. [64] developed a facile low-temperature hydrothermal method to prepare anatase titania/cellulose aerogels with strong photocatalytic
activities. This involved low-temperature hydrothermal preparation of ATC aerogel.
Zhang et al. [65] also reported a new type of multifunctional TiO 2 –graphene
nanocomposite hydrogel (TGH) by a similar one-pot hydrothermal approach and
explored its environmental and energy applications as photocatalyst, reusable adsorbents, and supercapacitor.
Our recently research also found that the hydrothermal–freeze-drying method is a
very convenient technology to prepare the TiO 2 /GAs aerogel [66]. Very
118
5 Graphene-Modified TiO 2 with Enhanced Visible Light Photocatalytic Activities
graphene–TiO 2 NPs, which confirmed high photoactivity of graphene–TiO 2 NPs
under visible light irradiation. Additionally, our recent research work demonstrated
that the P25/graphene composite could produce the electrons and exhibit a high
photocurrent response under the simulated solar light irradiation (Fig. 5.10d) [48].
5.2.2 Three-Dimensional TiO 2 /Graphene Composite
In addition to 2D-structured composites, the 3D-structured TiO 2 /graphene composites also attracted intense attention in recent years. Compared to the 2D-structured
graphene, 3D graphene such as hydrogel or aerogel has some unique properties. For
example, it has an ultra-low density, three-dimensional network structure, controllable morphology, controllable mechanical strength, excellent electrical conductivity, and strong adsorption for the gasoline and other organic compounds [61–63].
The unique and outstanding performance of 3D graphene mentioned above
determines that the composite of semiconductors compounded with the 3D graphene
has a broad application prospect in the field of environment protection and energy
storage. For photocatalysis application, the TiO 2 -based materials are still the predominant photocatalysts owing to fruitful achievements realized by so many
researchers. Thus, in this section, we also would like to give a simple summarization
of the 3D-structured TiO 2 /graphene composites and applications in photocatalysis.
5.2.2.1 Preparations
Generally, there are three synthesized methods including the evaporation-induced
self-assembly, hydrothermal–freeze-drying, and thermal reduction for the preparation of TiO 2 /graphene hydrogen or aerogel.
The hydrothermal technology is still the main preparation method for the synthesis of 3D-structured TiO 2 /graphene composites. Different from the preparation of
2D-structured TiO 2 /graphene by the hydrothermal method, the freeze-drying after
treatment plays an important role in the establishment of 3D network structure
during the hydrothermal process. A room-temperature or high-temperature drying
will destroy the skeleton of 3D graphene, resulting in the failure of the formation of
aerogel or hydrogel. Wan et al. [64] developed a facile low-temperature hydrothermal method to prepare anatase titania/cellulose aerogels with strong photocatalytic
activities. This involved low-temperature hydrothermal preparation of ATC aerogel.
Zhang et al. [65] also reported a new type of multifunctional TiO 2 –graphene
nanocomposite hydrogel (TGH) by a similar one-pot hydrothermal approach and
explored its environmental and energy applications as photocatalyst, reusable adsorbents, and supercapacitor.
Our recently research also found that the hydrothermal–freeze-drying method is a
very convenient technology to prepare the TiO 2 /GAs aerogel [66]. Very
118
5 Graphene-Modified TiO 2 with Enhanced Visible Light Photocatalytic Activities