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Journal of Materials Chemistry A
Page 9 of 11
Journal Name
ARTICLE
composite samples with rising temperature.59 Therefore, local
photothermal effect of carbon also has positive effects on the
activity of photocatalytic CO2 reduction over the
nanocomposites.
1
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DOI: 10.1039/C6TA11121A
S. Yan, S. Ouyang, H. Xu, M. Zhao, X. Zhang and J. Ye, J.
Based on the above results, a probable reaction mechanism
for photocatalytic over carbon@TiO2 composites is proposed
and illustrated in Scheme 2. Firstly, CO2 is adsorbed on the
surface of TiO2 hollow spheres. Meanwhile, the CO2 adsorption
on CNS core also plays a very important role via π–π
conjugation interaction. During light irradiation, charge
separation occurs in TiO2 generating a large amount of
electron-hole pairs. The electron-hole pairs were separated and
the electrons transferred through carbon materials. Then
electrons initiated photocatalytic reduction reaction by reacting
with CO2 and water. Water was oxidized by holes, generating
oxygen and H+ ions. And CO2 was reduced into methane and
methanol by reaction with H+ ions and electrons.60,61
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,
,
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In this process, difference in the quasi Fermi energies
created nonequilibrium charging state between TiO2 and
carbon. Thus, these photoexcited electrons transfer from
conduction band (CB) of TiO2 to neighboring carbon. The
process improves electron transfer efficiency, which leads to
charge equilibrium between these two components in the
composite materials. Moreover, the electron transfer to CNS
reduces the amount of electrons in the lattice of TiO2, which
can hinder electron-hole recombination efficiently and allow
more holes to be generated on the TiO2 surface for the
oxidation of water. Therefore, overall photocatalytic activity of
the carbon@TiO2 nanocomposites can be enhanced during the
process.
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Conclusions
In summary, a hybrid carbon@TiO2 hollow spherical structure
was fabricated by a facile and green method. The as-designed
hybrid semiconductor@carbon products not only enhanced the
visible-light absorption and CO2 adsorption, but also improve
the photogenerated charge transfer efficiency. As a result, the
hybrid carbon@TiO2 photocatalyst exhibited a much higher
activity for photocatalytic CO2 reduction and produced more
variety of solar fuels compared with P25. The approach for
fabricating the hybrid nanostructure may also bring new
insights for a variety of semiconductor-based applications such
as supercapacitor, catalysis, sensors and energy conversion.
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Acknowledgements
This study was partially supported by the 973 program
(2013CB632402), NSFC (51572209, 51320105001, 51372190,
21433007 and 21573170). Also, this work was financially
supported by the Natural Science Foundation of Hubei Province
of China (2015CFA001), the Fundamental Research Funds for
the Central Universities (WUT: 2015-III-034) and Innovative
Research Funds of SKLWUT (2015-ZD-1)
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References
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