3. Recent progress on the development of g-C3N4 photocatalyst for environmental remediation

•O2

Nanocatalysts

Modification method

Non-metal doping

Noble metal deposition

Hybridizing g-C3N4 with carbon nanomaterials (CNM)

Coupling g-C3N4 with semiconductor

Table 1.

34

Metal doping Doping of various metallic

g-C3N4

metals

(RGO)

species such as the alkali metals, rare earth metals and noble metals into

Doping g-C3N4 with non-

Deposition of noble metal nanoparticles such as Cu, Pt, Au and Pd on g-C3N4

Carbon nanomaterial such as carbon nanotubes (CNTs), carbon nanospheres (CNS), graphene oxide (GO) and reduced graphene oxide

Coupling two or more semiconductors to form a

Surface modification of g-C3N4 technique to improve its photocatalytic performance.

semiconductor heterojunction

� þ recalcitrant pollutants ! degradation of pollutant (4) •OH þ recalcitrant pollutants ! degradation of pollutant (5)

In order to overcome the individual drawback of pure g-C3N4, many attempts have been made to improve the photocatalytic capability including surface modification of the photocatalyst structure. Generally, the surface modification aims to improve the photocatalyst specific surface area, charge separation and optical. There are currently five modification techniques which have been investigated including the introduction of heteroatoms (i.e. metals and non-metals) within g-C3N4 framework, noble metal deposition, hybridizing g-C3N4 with carbon nanomaterials and coupling g-C3N4 with a photocatalyst. The principle, advantages

On the other hand, the development of the heterostructure photocatalyst via the introduction of additional compounds into the g-C3N4 network is one of the most promising strategies to enhance the overall catalytic performance of g-C3N4 photocatalyst [22]. In general, the g-C3N4-based heterostructure can be developed by coupling the g-C3N4 with other types of photocatalyst as co-catalyst. The formation of the heterostructure with suitable band position would suppress the recombination rate of the photogenerated electron–hole pairs, which lead to higher

Principle Advantages Disadvantages

Bandgap narrowing, surface area improvement, charge separation and finetuning the band structure

No secondary pollution, improve visible light absorption and charge

Metal content positively

High thermal, electronic conductivity, remarkable adsorption properties for organic and inorganic compounds

Improved stability, visible light utilization, charge separation and transfer and more efficient formation of the oxidizing species

photocatalytic activity until the optimum loading is

separation

influence the

reached

Can often cause secondary pollution due to leaching of the metal ions

Non-metal species does not take part in charge transportation hence recombination centers are

Beyond the optimum metal loading, the excess metal ions act as recombination centers for the electron/hole pairs

Excess CNM (i.e. RGO) facilitate adsorption of large amounts of the dye molecules onto the catalyst surface thereby reducing light penetration to the photocatalyst

Difficult to find a proper semiconductor

photocatalyst with suitable band edge position

formed

2.5 Strategies to improve g-C3N4 photocatalytic performance

and disadvantages of each technique are summarized in Table 1.


Nanostructures & Nanodevices (COINN), Universiti Teknologi PETRONAS and The Murata Science Foundation Grant (015ME0-033) for the financial and laboratory support. The authors would like to thank the Centre Analytical Lab, Universiti Teknologi PETRONAS for the sample characterization facilities.

Recent Development of Graphitic Carbon Nitride-Based Photocatalyst for Environmental…

Mohamad Fakhrul Ridhwan Samsudin, Nurfatien Bacho and Suriati Sufian\*

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Chemical Engineering Department, Universiti Teknologi Petronas,

Conflict of interest

Author details

37

Bandar Seri Iskandar, Perak, Malaysia

provided the original work is properly cited.

\*Address all correspondence to: suriati@utp.edu.my

The authors declare no conflict of interest.

DOI: http://dx.doi.org/10.5772/intechopen.81639

### 4. Conclusions and future directions

The growing concern over the scarcity of clean water sources due to a fast development of industrialization has force a rapid breakthrough dedicated to the development of advanced photocatalyst system. Over the past few years, the studies on g-C3N4 based photocatalyst have witnessed auspicious potential promises by this photocatalyst in environmental remediation applications. To date, the profound photocatalytic performance of g-C3N4 based photocatalyst is mainly governed by its intrinsic features such as metal-free photocatalyst and good light absorption properties owing to its medium band-gap energy of 2.7 eV. In this chapter, the synthesis, properties and photocatalytic application of g-C3N4 are summarized. Then, the most recent strategies for enhancing the photocatalytic performance of the g-C3N4 photocatalyst are highlighted.

Although profound performance had been reported in most of the recent studies, the promising potential of g-C3N4 based photocatalyst has yet to be exploited fully. The main challenges which are yet to be mitigated are (i) green synthesizing method which can produce high surface area and good photostability photocatalyst, (ii) the control of surface kinetics on g-C3N4 photocatalyst which can promote the photocharge separation and migration, (iii) the use of real industrial wastewater in analyzing the performance of g-C3N4 based photocatalyst, (iv) improving the reactor design to achieve the optimum photocatalytic performance with the lowest cost and (v) the utilization of real sunlight as a light source during the analysis process.

#### Acknowledgements

The authors would like to express their appreciation to the Chemical Engineering Department, Universiti Teknologi PETRONAS, Centre of Innovative Recent Development of Graphitic Carbon Nitride-Based Photocatalyst for Environmental… DOI: http://dx.doi.org/10.5772/intechopen.81639

Nanostructures & Nanodevices (COINN), Universiti Teknologi PETRONAS and The Murata Science Foundation Grant (015ME0-033) for the financial and laboratory support. The authors would like to thank the Centre Analytical Lab, Universiti Teknologi PETRONAS for the sample characterization facilities.
