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RSC Advances
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DOI: 10.1039/C6RA11446F
Journal Name
ARTICLE
suppresses the recombination rate of the photogenerated
carriers, thus improves the photocatalytic activity.
Conclusions
Highly effective photocatalyst of ZnO:P/GNDs composites is
-1
acheived and it possess a photoxidation rate of 0.44 min for
RhB degration under simulated sunlight irradiation, which is
about 3 times larger than that of pritine ZnO:P nanosheets.
The exceptional photocatalytic activity of the ZnO:P/GNDs
composites can be attributed to the role of GNDs actinig as
photoabsorber and charge separation channels, and the
synergetic effects between the ZnO:P nanosheets and GNDs
for enhancement of light adsorption efficiency, suppression of
charge recombination, and improvement of interfacial charge
transfer. This study will provide important inspirations for the
design of novel high efficient photocatalysts.
Fig. 5 A tentative mechanism of photodegradation process of
ZnO:P/GNDs composites.
Figure 5 illustrates the photodegradation mechanism of
ZnO:P/GNDs composites. The proposed reaction processes
2
4
involved are as follows:
+
ZnO(h ) + ZnO(e )
-
Acknowledgements
ZnO + h
-
ZnO(e )
ν
→
→
-
GNDs(e ) (electron migration)
This work was supported by the National Natural Science
Foundation of China (51402193, 51572173 and 11402149),
Natural Science Foundation of Shanghai (14ZR1428000),
Science and Technology Innovation Action Plan International
Cooperation Programme of Shanghai (15520720300), Shanghai
Talent Development Funding and the Hujiang Foundation of
China (B14006).
-
-
•O + GNDs
GNDs(e ) + O
+
h + H O
→
2
2
+
→
•OH + H
-
2
-
O + H
+
•
→
HO
2
2
+
-
HO + •O + H
-
→ H O + O
2 2 2
-
•OH + OH + O
2
2
-
H O + O
2
→
2
2
2
-
-
H
2
O
2
+ e
→
•OH + OH
Dye + •OH
2 2
→ CO + H O
When irradiated by photons with energy higher than the
bandgap of ZnO:P nanosheets, the photogenerated electrons
Notes and references
2 2
and holes reacted with O and H O on the surface of ZnO
1
2
3
4
5
6
7
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, 1709-1712.
nanosheets, respectively. The reactions generate highly
reactive •OH to degrade organic molecules. Ultrathin ZnO:P
nanosheets with high surface-to-volume ratio provide a large
interfacial area for the absorption of incident photons, and
offer the intimate contact with GNDs. Meanwhile, when the
RhB molecules come into contact with GNDs, they are stuck to
the surface of composites through strong π-π interactions with
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2
6
ZnO to GNDs. Due to the heterojunction at the interface
between ZnO and GNDs as well as the excellent charge-carrier
mobility, the photogenerated electrons can be smoothly
transferred to the GNDs sites, which effectively separated the
electrons and the holes. Consequently, more photogenerated
electrons and holes involve in the photocatalytic processes,
and the photocatalytic activity of the ZnO:P/GNDs nanosheet
composite is significantly enhanced. Therefore, GNDs not only
act as electron acceptors but also as electron-transport
pathway, resulting in the inhibition of charge recombination,
thus an enhancement of photodegradation rate is achieved.
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