times an improvement in the photocatalytic performance compared to the commercial WO 3 (An et al. 2012). Gao et al. (2011) observed a threefold increase in the
performance of Bi 2 WO 6 /graphene composite toward the degradation of RhB dye
compared to pure Bi 2 WO 6 . This improvement is due to the Fermi energy level shift
and efficient transfer of photoinduced electrons at the Bi 2 WO 6 /graphene interface.
The visible photocatalytic activity of ZnWO 4 hybridization with graphene sheet was
attributed to the efficient transfer of charge carriers at the ZnWO 4 /graphene interface
(Bai et al. 2012). Moreover, carbon free radicals, which was found along with the
O 2
À• and HO
• radicals, did not directly partake in the photodegradation reaction but
to some degree enhanced their lifetime for the oxidative reactions. Zhang et al.
(2011b) showed 1.87 times photocatalytic performance of InNbO 4 /graphene compared to pure InNbO 4 for the degradation of MB dye. Iron nanoparticles/graphene
composites, which was successfully fabricated using graphene oxide as a supporting
matrix, showed a higher elimination capacity to decolorize methylene blue dye (Guo
et al. 2012). The graphene/Mn 2 O 3 nanocomposite with a uniform distribution of
Mn 2 O 3 nanoparticles throughout the surface of graphene sheet showed $60, $80,
and $84% degradation of RhB, eosin, and MB dyes, respectively (Chandra et al.
2012). The graphene/Cu 2 O composites, which were fabricated at room temperature
using a one-pot solution route, altered the surface charge of the composites from
positive to negative (Gao et al. 2012a). This favors the adsorption and photocatalytic
degradation of MB dyes under simulated visible light irradiation. Through a simple
solvothermal route, graphene/CdS composite was fabricated (Gao et al. 2012b). The
as-fabricated composites showed an effective migration of photoinduced electrons
from CdS to graphene sheet, as well as enhanced visible light photodegradation
activity for RhB dye degradation. The CeO 2 /TiO 2 /graphene composites synthesized
by the sol–gel process exhibited a higher photocatalytic degradation of
2,4-dichlorophenoxyacetic acid and Reactive Red 195 dye in aqueous solution
(Ghasemi et al. 2012). A BiVO 4 /graphene composite was fabricated via a one-step
hydrothermal route (Fu et al. 2011). The as-fabricated composite showed enhanced
photoactivity for the decomposition of MO, RhB, MB, and active black BL-G dyes
in water. This improvement was attributed to the effective separation of charge
carriers and the concerted effects of pure BiVO 4 and graphene sheet. Through a
hydrothermal method, copper oxide was effectively decorated with functionalized
graphene sheets (Yusoff et al. 2013). Due to the enhanced synergy interactions
between copper oxide and functionalized graphene sheets, the nanocomposite demonstrated higher photoactivity toward the degradation of MB dye. The SnO 2 /
graphene and Cu 2 O/SnO 2 /graphene nanocomposites fabricated by simple sol–gel
growth route showed a higher photodegradation of pendimethalin than pure SnO 2
and pristine graphene (Wang et al. 2013e). The novel graphene/Sb 2 S 3 composites
prepared using a facile solvothermal method revealed improved photodegradation
activity toward RhB dye due to the negative surface charge, efficient electrons
transfer from Sb 2 S 3 to the graphene sheet, and smaller Sb 2 S 3 particles size (Tao
et al. 2013). Within the two-step hydrothermal approach, the La-TiO 2 /graphene
composites have better charge separation ability and enhanced photodegradation
of MB dye with reference to pure TiO 2 (Khalid et al. 2012b). The high performance
1 Nanotechnology for Water and Wastewater Treatment Using Graphene. . .
19
performance of Bi 2 WO 6 /graphene composite toward the degradation of RhB dye
compared to pure Bi 2 WO 6 . This improvement is due to the Fermi energy level shift
and efficient transfer of photoinduced electrons at the Bi 2 WO 6 /graphene interface.
The visible photocatalytic activity of ZnWO 4 hybridization with graphene sheet was
attributed to the efficient transfer of charge carriers at the ZnWO 4 /graphene interface
(Bai et al. 2012). Moreover, carbon free radicals, which was found along with the
O 2
À• and HO
• radicals, did not directly partake in the photodegradation reaction but
to some degree enhanced their lifetime for the oxidative reactions. Zhang et al.
(2011b) showed 1.87 times photocatalytic performance of InNbO 4 /graphene compared to pure InNbO 4 for the degradation of MB dye. Iron nanoparticles/graphene
composites, which was successfully fabricated using graphene oxide as a supporting
matrix, showed a higher elimination capacity to decolorize methylene blue dye (Guo
et al. 2012). The graphene/Mn 2 O 3 nanocomposite with a uniform distribution of
Mn 2 O 3 nanoparticles throughout the surface of graphene sheet showed $60, $80,
and $84% degradation of RhB, eosin, and MB dyes, respectively (Chandra et al.
2012). The graphene/Cu 2 O composites, which were fabricated at room temperature
using a one-pot solution route, altered the surface charge of the composites from
positive to negative (Gao et al. 2012a). This favors the adsorption and photocatalytic
degradation of MB dyes under simulated visible light irradiation. Through a simple
solvothermal route, graphene/CdS composite was fabricated (Gao et al. 2012b). The
as-fabricated composites showed an effective migration of photoinduced electrons
from CdS to graphene sheet, as well as enhanced visible light photodegradation
activity for RhB dye degradation. The CeO 2 /TiO 2 /graphene composites synthesized
by the sol–gel process exhibited a higher photocatalytic degradation of
2,4-dichlorophenoxyacetic acid and Reactive Red 195 dye in aqueous solution
(Ghasemi et al. 2012). A BiVO 4 /graphene composite was fabricated via a one-step
hydrothermal route (Fu et al. 2011). The as-fabricated composite showed enhanced
photoactivity for the decomposition of MO, RhB, MB, and active black BL-G dyes
in water. This improvement was attributed to the effective separation of charge
carriers and the concerted effects of pure BiVO 4 and graphene sheet. Through a
hydrothermal method, copper oxide was effectively decorated with functionalized
graphene sheets (Yusoff et al. 2013). Due to the enhanced synergy interactions
between copper oxide and functionalized graphene sheets, the nanocomposite demonstrated higher photoactivity toward the degradation of MB dye. The SnO 2 /
graphene and Cu 2 O/SnO 2 /graphene nanocomposites fabricated by simple sol–gel
growth route showed a higher photodegradation of pendimethalin than pure SnO 2
and pristine graphene (Wang et al. 2013e). The novel graphene/Sb 2 S 3 composites
prepared using a facile solvothermal method revealed improved photodegradation
activity toward RhB dye due to the negative surface charge, efficient electrons
transfer from Sb 2 S 3 to the graphene sheet, and smaller Sb 2 S 3 particles size (Tao
et al. 2013). Within the two-step hydrothermal approach, the La-TiO 2 /graphene
composites have better charge separation ability and enhanced photodegradation
of MB dye with reference to pure TiO 2 (Khalid et al. 2012b). The high performance
1 Nanotechnology for Water and Wastewater Treatment Using Graphene. . .
19