Environmental Engineering Reference
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Fig. 18 TEM images of (G-Ti
0.91
O
2
)
5
hollow spheres (a) and rutile TiO
2
/graphene quantum dot
composites (d). b PL emission spectra of (Ti
0.91
O
2
)
5
hollow spheres and (G-Ti
0.91
O
2
)
5
hollow
spheres (a). c Photocatalytic CH
4
and CO evolution rates for (Ti
0.91
O
2
)
5
hollow spheres
(G-Ti
0.91
O
2
)
5
hollow spheres (a) and P25. e Upconverted PL spectra of the graphene quantum
dots (b) at different excitation wavelengths and f photocatalytic degradation of MB under visible
light irradiation using different catalysts. (Reprinted with permission from Ref. a-c [
380
],
d-f [
388
]. Copyright Wiley-VCH and American Chemical Society)
layer-by-layer assembly technique with polymer PMMA beads as sacrificial
templates. Subsequently, microwave irradiation was used to simultaneously
remove the template and reduce graphene oxide into graphene. The sufficiently
compact stacking of ultrathin Ti
0.91
O
2
nanosheets with graphene nanosheets
facilitated the photogenerated electron to quickly transfer from the Ti
0.91
O
2
nanosheets to graphene and enhance the lifetime of the charge carriers and
improve photocatalytic activity (Fig.
18
b, c) [
380
].
In the fourth method, the in situ growth of TiO
2
structures and reduction of GO are
simultaneously accomplished through a simple one-pot growth method [
381
,
382
].
This strategy is a particularly convenient procedure for the fabrication of graphene-
TiO
2
photocatalysts. The reducing environment can be achieved by using either a
reducing solvent or by directly adding a reducing agent [
383
,
384
]. For example,
exposed (001) facet TiO
2
-graphene composite photocatalysts were successfully
produced via a direct one-step hydrothermal method in an ethanol-water solvent.
The resulting composite exhibited an extended visible light absorption range due to
the formation of a chemical Ti-O-C bond and enhanced charge separation by virtue
of the formation of nano-sized Schottky interfaces at the contacts between TiO
2
and
graphene. This leads to significant improvement in photodegredation of MB (or MO)
dye when compared to P25 films under both UV and visible light irradiation [
367
].
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