Short communicationSimple synthesis of Zr-doped graphitic carbon nitride towards enhanced photocatalytic performance under simulated solar light irradiation
Graphical abstract
The proposed mechanism for the enhanced photocatalytic activity of Zr-doped g-C3N4: with a suitable doping concentration, the doped Zr species in lattice structure of g-C3N4 served to meliorate the electronic conductivity, which significantly suppressed the recombination of photogenerated electron–hole pairs and lead to a higher energy efficiency.
Introduction
In recent years, the direct application of solar energy through semiconductor based photocatalysis for environmental pollution control has attracted great research interests [1], [2], [3]. However, traditional metal oxide photocatalysts can only be excited with ultraviolet (UV) light due to their wide bandgap. In order to make more use of the solar light, intensive efforts have been devoted to preparing visible light driven photocatalysts [4], [5]. Recently, a metal-free polymeric semiconductor graphitic carbon nitride (g-C3N4) has drawn much attention because of its narrow bandgap (2.7 eV), non-toxic nature and inexpensive properties [6], [7], [8], [9]. Meanwhile, owing to its tri-s-triazine ring structure and high degree of condensation, the g-C3N4 exhibits good thermal and chemical stability [10], [11], [12]. Although pristine g-C3N4 reveals good photocatalytic properties, it still has many drawbacks, such as high recombination rate of photogenerated electron–hole pairs, low electrical conductivity and poor specific surface area. Therefore, many attempts have been made to improve the photocatalytic activity of g-C3N4, such as designing appropriate textural properties [13], [14], loading cocatalysts on the g-C3N4 surface [15], doping [8], [16], preparation of porous g-C3N4 [17] and heterojunctions with other semiconductors [18], [19]. Among different strategies, it is well recognized that metal doping is one of the most effective methods to implement visible light absorption expansion and specific surface area promotion. Because of the high cost of noble metal as well as the complicated fabrication processes which inhibit their practical applications, it is necessary to develop other elements doped g-C3N4 photocatalysts. More recently, the synthesis of bandgap narrowed Zr doped photocatalysts such as Zr–CeO2 and Zr–TiO2 with high photocatalytic activity has been realized. Furthermore, the formation of the hollow mesoporous structure of semiconductor photocatalysts is strongly dependent on the addition of Zr4 + ions [20], [21]. However, to the best of our knowledge, there were no reports on improved photocatalytic performance of g-C3N4 by Zr doping.
Herein, we report a simple pyrolysis method for the synthesis of Zr-doped g-C3N4 materials by using urea as the precursor [22] and zirconium nitrate as the Zr source. The g-C3N4 hybridized with Zr was found to readily narrow the bandgap of g-C3N4 and enhance visible light absorption. Furthermore, the photocatalytic activity and synergistic effect of the Zr-doped g-C3N4 were investigated and discussed in detail.
Section snippets
Material synthesis
Zirconium nitrate (analytical reagent 99.7%), urea and ethanol (chemically pure 99.5%) were purchased from Shanghai Chemical Corp. All chemicals involved were used for experiments without any further purification. Zr-doped g-C3N4 materials were synthesized as follows. Typically, various amounts of zirconium nitrate were dissolved in 10 mL of ethanol under magnetic stirring, and then 10 g of urea was dispersed in the solution with stirring for minutes, and then poured into Petri dishes to
Results and discussion
Fig. 1(a) shows the XRD patterns of the synthesized Zr-doped g-C3N4 materials with various Zr doping concentrations. The typical (002) interlayer-stacking peak at 27.3° corresponded to an interlayer distance of d = 0.32 nm for g-C3N4, while the peak at 13.1° represented an in-plane structural packing motif (100) with a period of 0.675 nm [11], [20]. It can be seen that the diffraction peaks of all the samples could be assigned to the structure of a typical graphitic carbon nitride, and no
Conclusions
Zr-doped g-C3N4 catalysts were successfully synthesized with a simple pyrolysis method. The prepared Zr-doped g-C3N4 catalysts exhibited much greater photocatalytic activity than pure g-C3N4 for the degradation of RhB dye under simulated solar light irradiation, and the 0.5Zr/g-C3N4 sample possessed the greatest activity. The XRD, nitrogen sorption, and TEM results revealed that the obtained Zr-doped g-C3N4 catalysts contain hierarchical porosity and high specific surface area. The idea of
Acknowledgments
This research work was supported by the National Natural Science Foundation of China (Grant No. 21103024 and 51502172), Program of Shanghai Pujiang Talent Plan (Grant No. 14PJ1406800), and Capacity-Building of Local University Project by the Science and Technology Commission of Shanghai Municipality (Grant No. 12160502400).
References (26)
Mater. Lett.
(2011)- et al.
Appl. Surf. Sci.
(2014) - et al.
Appl. Surf. Sci.
(2015) - et al.
Appl. Catal. B Environ.
(2014) - et al.
Appl. Catal. B Environ.
(2014) - et al.
Appl. Catal. B Environ.
(2015) - et al.
J. Solid State Chem.
(2009) - et al.
Appl. Catal. B Environ.
(2015) - et al.
J. Phys. Chem. Lett.
(2014) - et al.
Ind. Eng. Chem. Res.
(2013)