Chapter 5
Graphene-Modified TiO 2 with Enhanced
Visible Light Photocatalytic Activities
5.1 Introduction
With the development of nanotechnology, nanomaterials have attracted plenty of
attentions in the field of photocatalysis. Especially, semiconductor gradually
becomes a hot spot for researchers due to its low cost and high activity. In 1972,
Fujishima and Hoda reported that the H 2 could be produced by the TiO 2 electrodes
under the light irradiation [1]. Since then, TiO 2 has become one of the most
promising oxide semiconductors and been used in solar energy cells and air and
wastewater purifiers [2–5]. Due to its high photostability, nontoxic, low cost, high
activity, and so on [6–8], its research in the field of photocatalysis has made a great
progress in recent years. However, for the heterogeneous photocatalysis, there are
still some limitations in the applications of TiO 2 , which could not be ignored. For
instance, the photon flux of TiO 2 in the process of photoreaction is very easy to reach
saturation under the weak light irradiation, which will significantly reduce the energy
efficiency of the whole process during wastewater purification [9–12]. What is more,
the largest limitation of TiO 2 application is that it can only absorb the UV light less
than 387 nm [13]. In other words, the TiO 2 can only effectively utilize less than 6%
of the energy derived from the sunlight, which suggests its low potential of sustainable development in the photocatalysis.
Due to the existence of these mentioned drawbacks, many modifications have
been done on TiO 2 , including nonmetal doping [9, 14–17], metal doping [11, 18–
24], semiconductor compound modification [25–29], and organic photosensitization
[17, 30]. However, these modifications also have some limitations. For instance, the
nonmetal doping and metal doping on the surface of TiO 2 will lead to the decrease of
thermal stability of crystals and also introduce the traps to capture the photogenerated carriers on the surface or in the bulk of catalysts. As a result, it can
produce a large number of electron–hole recombination centers [19], which will
reduce its photocatalytic activities. Until the introduction of graphene, a visible light© Springer Nature Singapore Pte Ltd. 2018
J. Zhang et al., Photocatalysis, Lecture Notes in Chemistry 100,
https://doi.org/10.1007/978-981-13-2113-9_5
107
Graphene-Modified TiO 2 with Enhanced
Visible Light Photocatalytic Activities
5.1 Introduction
With the development of nanotechnology, nanomaterials have attracted plenty of
attentions in the field of photocatalysis. Especially, semiconductor gradually
becomes a hot spot for researchers due to its low cost and high activity. In 1972,
Fujishima and Hoda reported that the H 2 could be produced by the TiO 2 electrodes
under the light irradiation [1]. Since then, TiO 2 has become one of the most
promising oxide semiconductors and been used in solar energy cells and air and
wastewater purifiers [2–5]. Due to its high photostability, nontoxic, low cost, high
activity, and so on [6–8], its research in the field of photocatalysis has made a great
progress in recent years. However, for the heterogeneous photocatalysis, there are
still some limitations in the applications of TiO 2 , which could not be ignored. For
instance, the photon flux of TiO 2 in the process of photoreaction is very easy to reach
saturation under the weak light irradiation, which will significantly reduce the energy
efficiency of the whole process during wastewater purification [9–12]. What is more,
the largest limitation of TiO 2 application is that it can only absorb the UV light less
than 387 nm [13]. In other words, the TiO 2 can only effectively utilize less than 6%
of the energy derived from the sunlight, which suggests its low potential of sustainable development in the photocatalysis.
Due to the existence of these mentioned drawbacks, many modifications have
been done on TiO 2 , including nonmetal doping [9, 14–17], metal doping [11, 18–
24], semiconductor compound modification [25–29], and organic photosensitization
[17, 30]. However, these modifications also have some limitations. For instance, the
nonmetal doping and metal doping on the surface of TiO 2 will lead to the decrease of
thermal stability of crystals and also introduce the traps to capture the photogenerated carriers on the surface or in the bulk of catalysts. As a result, it can
produce a large number of electron–hole recombination centers [19], which will
reduce its photocatalytic activities. Until the introduction of graphene, a visible light© Springer Nature Singapore Pte Ltd. 2018
J. Zhang et al., Photocatalysis, Lecture Notes in Chemistry 100,
https://doi.org/10.1007/978-981-13-2113-9_5
107