Unique bar-like sulfur-doped C3N4 /TiO2 nanocomposite

Significance 

The need to protect the environment, conserve energy and reduce carbon dioxide emission is currently a global objective among researchers and policymakers. Currently, photocatalytic technology is considered a promising solution in environmental protection and energy conservation owing to its environmental benefits and low cost. Of all the various photocatalytic available, titanium oxide (TiO2) is widely preferred due to its stability, low cost and high efficiency. Unfortunately, it is associated with a quick recombination of the photoinduced electrons and a wide band gap that limits its efficiency. Therefore, significant efforts have been directed towards offering solutions to this problem.

Among the proposed methods, narrow band gap heterojunction is capable of not only suppressing the recombination of the charge carriers but also allowing the photocatalytic capability in the presence of visible light. Consequently, a hybrid of g-C3N4 with TiO2 exhibit enhanced photocatalytic performance in the presence of visible light. This is due to the unique physical and chemical properties of g-C3N4. However, g-C3N4/TiO2 hybrid composite has disadvantages resulting from insufficient absorption of light and separation of photogenerated charge carriers that limit its effectiveness. Also, the large energy surface leads to the aggregation of TiO2 nanoparticles on the g-C3N4 substrate.

In a recently published literature, sulfur doping has been utilized to improve the photocatalytic activities of g-C3N4. This has significantly attracted interests amongst researchers as it possesses the desirable electronic structure and efficiency in the photo-induced electron transportation. However, little has been reported about coupling S-C3N4 and TiO2.

Shandong University researchers led by Professor Shiping Xu used a facile impregnation technique to fabricate a nanocomposite of TiO2 nanoparticles coupled with a sulfur-doped C3N4 layer (SCNT). For the synthesis, the group of authors utilized tri-t hiocyanuric acid as a precursor for sulfur. Their work is currently published in the journal, Applied Surface Science.

The authors observed that the fabricated nanocomposite exhibited significantly improved photocatalytic activities in the removal of pollutants as compared to pure TiO2 and g-C3N4 /TiO2. For instance, a rate constant of 8.6 and 2.6 times more than that obtained in pure titanium oxide and g-C3N4 /TiO2 composite respectively was achieved during the degradation of MO. Additionally, the synthesized SCNT exhibited strong capability for absorption of visible light.

The study by Shandong University scientists is the first to successfully synthesize sulfur-doped coupling of g-C3N4 and pure TiO2. The improvement in the photocatalytic efficiency of the resultant nanocomposite was attributed to its capability of inhibiting the aggregation of TiO2 nanoparticles on the g-C3N4 substrate as well as suppressing the recombination of photoinduced electron pairs. Consequently, the introduced sulfur regulated g-C3N4 morphology thus resulting in the formation of ultrathin g-C3N4 layer and bar-like g-C3N4 /TiO2 nanocomposite which enhanced its entire efficiency like visible light absorption capacity.  Therefore, their work is a promising solution for the synthesis and use of highly efficient photocatalyst in the presence of visible light irradiation for environmental purification and pollutants removal.

Unique bar-like sulfur-doped C3N4 /TiO2 nanocomposite - Advanced Engineering
Figure 1 Mechanism of fast charge tansfer at the interface between (a) C3N4-TiO2 and (b) S-C3N4/TiO2

About the author

Shiping XU is associate professor in School of Environmental Science and Engineering at Shandong University, China. She received her PhD in Nanyang Technological University, Singapore in 2012. Her research interests focus on nanomaterials sysnthesis and advanced oxidation technologies for environmental purification. She has authored and co-authored more than 30 peer-reviewed papers, including J. Am, Chem. Soc., Advanced Functional Materials, Applied Catalysis B, etc..

About the author

Yu ZHAO received her BSc in environmental engineering from Xi’an petroleum University in 2016. She is currently a graduate student in the Department of Environmental science of Shandong University. Her research focuses on photocatalysis technology for antibiotic wastewater treatment, including the modification of g-C3N4 and the fabrication of heterojunction structure between g-C3N4 and other photocatalysts.

About the author

Xiang SUN received his bachelor and master degree from Department of Environmental Science and Technology in Shandong University. When he was a graduate student, he focused on the photocatalysis technology for antibiotic wastewater treatment, including synthesizing unique 3D hierarchical TiO2 microsphere structure and studying its degradation effect of antibiotics.

Reference

Zhao, Y., Xu, S., Sun, X., Xu, X., & Gao, B. (2018). Unique bar-like sulfur-doped C3N4/TiO2  nanocomposite: Excellent visible light driven photocatalytic activity and mechanism study. Applied Surface Science436, 873-881.

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