photodegradation of methyl orange under the solar light irradiation. The outstanding
transfer efficiencies of photo-generated carriers induced by the nanosized
compounding between TiO 2 and graphene were responsible for the enhancement
photocatalytic activity.
In addition to the colored dyes, some colorless organic compounds also can be
photodegraded by the graphene-based photocatalysts. In our previous work, the Ti
3+
-doped TiO 2 nanorods/boron-doped graphene composite was prepared by a hydrothermal method, and the synergistic effect on the visible light activity was investigated by the photodegradation of colorless phenol [20]. The TiO 2 /graphene
composite showed a higher photodegradation of phenol than other photocatalysts,
and the exposed (100) facets on TiO 2 , the self-doping of Ti
3+ , and the boron doped in
graphene were the reasons for the excellent photocatalytic activity. Ng et al. prepared
the electrodes which were consisted of TiO 2 /graphene nanocomposite. The
graphene-based electrodes had a significant activity for the complete photocatalytic
decomposition of 2,4-dichlorophenoxyacetic acid under the UV light irradiation.
Kamegawa et al. [50] designed a composite of TiO 2 nanoparticles supported on a
mesoporous silica surface (TiO 2 /MCM-41) which were selectively coated with
graphene through the formation of surface complexes between TiO 2 nanoparticles
and 2,3-dihydroxynaphthalene followed by carbonization under N 2 flow. The selective graphene modification induced the enhanced photocatalytic activities of TiO 2 /
MCM-41 for the decomposition of 2-propanol in water compared with unmodified
samples, owing to the appropriate adsorption properties of organics to transfer to the
surface of TiO 2 nanoparticles.
5.3.2 Water Splitting
Water splitting is another important application of the TiO 2 -based photocatalysis,
due to the exhaustion of energy in the world. The hydrogen is regarded as the clean
energy which is standing out in recent years owing to its low carbon consuming.
Fan et al. [69] developed a nanocomposite of TiO 2 and reduced graphene oxide as
an efficient photocatalysts for the H 2 evolution. As an ideal conductor, graphene
exhibited an excellent electron transfer capacity, leading to the enhancement of the
lifetime of photo-generated electrons which is the key factor for the high
photocatalytic water-splitting activity of the TiO 2 /graphene composite. Wang et al.
[70] reported the synthesis of graphene@TiO 2 nanocomposites with controlled
exposed crystal facets by a simple one-pot hydrothermal process. The prepared
TiO 2 /graphene composite showed an enhanced photocatalytic H 2 evolution under
the simulated solar light irradiation, owing to the exposed high reactive crystal facets
and high dispersed TiO 2 nanocrystals on graphene.
Li et al. [56] reported a reduced TiO 2 –graphene oxide heterostructure by a facile
chemical reduction method, which synthesized different samples named as sample
1 (1 mg GO/50 mg TiO 2 ), sample 2 (2 mg GO/50 mg TiO 2 ), sample 3 (3 mg
GO/50 mg TiO 2 ), and sample 4 (4 mg GO/50 mg TiO 2 ). The photocatalytic activity
124
5 Graphene-Modified TiO 2 with Enhanced Visible Light Photocatalytic Activities
transfer efficiencies of photo-generated carriers induced by the nanosized
compounding between TiO 2 and graphene were responsible for the enhancement
photocatalytic activity.
In addition to the colored dyes, some colorless organic compounds also can be
photodegraded by the graphene-based photocatalysts. In our previous work, the Ti
3+
-doped TiO 2 nanorods/boron-doped graphene composite was prepared by a hydrothermal method, and the synergistic effect on the visible light activity was investigated by the photodegradation of colorless phenol [20]. The TiO 2 /graphene
composite showed a higher photodegradation of phenol than other photocatalysts,
and the exposed (100) facets on TiO 2 , the self-doping of Ti
3+ , and the boron doped in
graphene were the reasons for the excellent photocatalytic activity. Ng et al. prepared
the electrodes which were consisted of TiO 2 /graphene nanocomposite. The
graphene-based electrodes had a significant activity for the complete photocatalytic
decomposition of 2,4-dichlorophenoxyacetic acid under the UV light irradiation.
Kamegawa et al. [50] designed a composite of TiO 2 nanoparticles supported on a
mesoporous silica surface (TiO 2 /MCM-41) which were selectively coated with
graphene through the formation of surface complexes between TiO 2 nanoparticles
and 2,3-dihydroxynaphthalene followed by carbonization under N 2 flow. The selective graphene modification induced the enhanced photocatalytic activities of TiO 2 /
MCM-41 for the decomposition of 2-propanol in water compared with unmodified
samples, owing to the appropriate adsorption properties of organics to transfer to the
surface of TiO 2 nanoparticles.
5.3.2 Water Splitting
Water splitting is another important application of the TiO 2 -based photocatalysis,
due to the exhaustion of energy in the world. The hydrogen is regarded as the clean
energy which is standing out in recent years owing to its low carbon consuming.
Fan et al. [69] developed a nanocomposite of TiO 2 and reduced graphene oxide as
an efficient photocatalysts for the H 2 evolution. As an ideal conductor, graphene
exhibited an excellent electron transfer capacity, leading to the enhancement of the
lifetime of photo-generated electrons which is the key factor for the high
photocatalytic water-splitting activity of the TiO 2 /graphene composite. Wang et al.
[70] reported the synthesis of graphene@TiO 2 nanocomposites with controlled
exposed crystal facets by a simple one-pot hydrothermal process. The prepared
TiO 2 /graphene composite showed an enhanced photocatalytic H 2 evolution under
the simulated solar light irradiation, owing to the exposed high reactive crystal facets
and high dispersed TiO 2 nanocrystals on graphene.
Li et al. [56] reported a reduced TiO 2 –graphene oxide heterostructure by a facile
chemical reduction method, which synthesized different samples named as sample
1 (1 mg GO/50 mg TiO 2 ), sample 2 (2 mg GO/50 mg TiO 2 ), sample 3 (3 mg
GO/50 mg TiO 2 ), and sample 4 (4 mg GO/50 mg TiO 2 ). The photocatalytic activity
124
5 Graphene-Modified TiO 2 with Enhanced Visible Light Photocatalytic Activities