- Email: [email protected]
Inorganic salt-assisted fabrication of graphitic carbon nitride with enhanced photocatalytic degradation of Rhodamine B
Materials Letters xx (xxxx) xxxx–xxxx
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Inorganic salt-assisted fabrication of graphitic carbon nitride with enhanced photocatalytic degradation of Rhodamine B ⁎
Lei Luoa, Anfeng Zhanga, Michael J. Janikb, Keyan Lia, Chunshan Songa,b, , Xinwen Guoa,
⁎
a State Key Laboratory of Fine Chemicals, PSU-DUT Joint Center for Energy Research, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China b EMS Energy Institute, PSU-DUT Joint Center for Energy Research and Department of Energy & Mineral Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
A R T I C L E I N F O
A BS T RAC T
Keywords: Porous materials Semiconductors Carbon materials
With the assistance of inorganic salt, graphitic carbon nitride nanosheets were prepared with increased mesoporous surface area for promoting the photocatalytic performance compared with the one without. Series of photocatalysts with different mass ratio of NH4NO3/melamine were prepared and characterized by XRD, FTIR, XPS, TEM, SEM, N2 physical adsorption, UV–vis and PL spectrometries. Photocatalytic degradation of RhB under visible light irradiation (λ > 420 nm) was applied to evaluate catalytic properties. The catalytic activity maximizes at an intermediate NH4NO3/melamine ratio at 0.15, giving a maximum performance, RhB totally being degraded within 30 min and kinetic constant reaching 0.167 min−1 that is 4.5 times as high as that on BCN. The NH4NO3 assisted procedure is a facile, repeatable, environmental friendly, and efficient method for preparing g-C3N4 nanosheets with high photocatalytic performance.
1. Introduction
C3N4 photocatalytic activity.
Graphitic carbon nitride (g-C3N4) is a promising metal-free visible light photocatalyst [1–3]. However, the photocatalytic activity of the pristine g-C3N4 is low due to its limited specific surface area, fast rate of charge recombination, and low electronic conductivity [4–6]. Hardtemplating method is a controllable, flexible and precise strategy for introducing a nanostructure, but the usage of hazardous fluoridecontained reagents (HF, NH4HF2) to remove the template as well as multiple step procedures with long operation periods limit its practical application. In contrast, top-down approaches such as liquid exfoliation [7–10] or thermal exfoliation [11–13] are utilized successfully to break the stacking system of bulk g-C3N4 to nanosheets and increase its photocatalytic activity. Though exfoliated nanosheets exhibit promoted photocatalytic activity with enhanced photoabsorption and photoresponse [8], their yield is still lower than 40% [5]. It would be advantageous to prepare g-C3N4 from one single step, with shorter preparation time, and with enhanced photocatalytic activity. In this work, g-C3N4 was synthesized by the thermal condensation of melamine, with the assistance of NH4NO3, to increase the specific mesoporous surface area, enhance the charge separation efficiency, and promote the photocatalytic performance. Photocatalytic degradation of RhB under visible light irradiation was performed to evaluate the g-
2. Experimental
⁎
Graphitic carbon nitride was synthesized from the thermal condensation of melamine with or without the assistance of NH4NO3. In a typical synthesis procedure, 3.0 g melamine precursor was mixed with a specified amount of NH4NO3 then ground to a fine powder. The powder was placed into a 30 mL covered crucible and heated in static air to 550 °C at a heating rate of 10 °C/min. After cooling, the obtained yellow product was ground for further characterization or evaluation. Samples are denoted as CNx where x/100 represents the mass ratio of NH4NO3/melamine. For sample CN15, the mass ratio of NH4NO3/ Melamine is 0.15. Bulk carbon nitride (BCN) was prepared without NH4NO3. The relevant characterization and evaluation can be found in Electronic Supplementary Information. 3. Results and discussion The crystal structure of the as-prepared samples BCN and CN15 were characterized with XRD, FT-IR, and XPS spectra, which together demonstrated the characteristic structure of g-C3N4 (shown in Fig. S1). The morphologies of the as-prepared catalysts were investigated with
Corresponding authors. E-mail address: [email protected] (X. Guo).
http://dx.doi.org/10.1016/j.matlet.2016.11.043 Received 20 September 2016; Received in revised form 8 November 2016; Accepted 9 November 2016 Available online xxxx 0167-577X/ © 2016 Elsevier B.V. All rights reserved.
Please cite this article as: Luo, L., Materials Letters (2016), http://dx.doi.org/10.1016/j.matlet.2016.11.043
Materials Letters xx (xxxx) xxxx–xxxx
L. Luo et al.
(b)
(a)
(c)
500 nm
4μm
(e)
(d)
500 nm
(f)
500 nm
200 nm
200 nm
Fig. 1. SEM (a) and TEM (d) images of BCN, SEM images of CN15 (b and c), TEM images of sample CN15 (e and f).
energy-wasting carrier recombination will be suppressed. The improved charge separation efficiency can be attributed to the pore structure and increased surface area that facilitates the transfer and separation of photogenerated charge carriers, prolongs their lifetime, and thus lowers the PL intensity [16]. The enhanced electron-hole separation efficiency may lead to improved photocatalytic quantum efficiency and activity. The photocatalytic degradation of RhB under visible light irradiation was applied as a probe reaction to evaluate the photocatalytic activity of the CNx samples. The amount of RhB adsorbed to the g-C3N4 before light irradiation was less than 20% for all CNx samples. As shown in Fig. 3a, RhB is degraded in the presence of each photocatalyst, however, the photocatalytic activity of all CNx samples exceeds BCN. The kinetic constants over the different photocatalysts are presented in Fig. 3b and c. BCN presents the lowest rate constant of k=0.037 min−1, and k increased significantly as the mass ratio of NH4NO3 increased. The kinetic constant reaches a maximum for CN15 at k=0.167 min−1. Further increasing the mass ratio of NH4NO3 led to a decrease of the kinetic constant. The enhanced photocatalytic activity arises from both an increase in surface area and increased electron-hole separation efficiency, as evidenced by the PL spectra. The increased specific surface area of the nanosheets can not only increase the active site, but also shorten the distance photogenerated electron-hole pairs migrate to reach the organic pollutant at the surface with the strong oxidative hole. For sample CN15, the reusability was also investigated by five consecutive reactivity studies (Fig. 3d). As the irradiation time was prolonged, RhB degraded without evident deactivation, which indicates stability of the CN15 photocatalyst.
TEM, SEM and nitrogen physical adsorption. Fig. 1 shows SEM and TEM images of the as-prepared sample BCN and CN15. The BCN sample is dense with a large particle size, whereas CN15 appears as a loose and soft material. The TEM images of CN15 show ultrathin nanosheets. By introducing NH4NO3, the layers of bulk g-C3N4 are separated, modifying the nanostructure. Nitrogen physical adsorption further supports the result obtained from SEM and TEM and adds quantitative analysis on the pore and textural properties. The adsorption-desorption isotherms are shown in Fig. S2, with textural properties presented in Table 1. By introducing NH4NO3, the SBET of CN15 is much higher than that of pristine BCN, suggesting that the gas products (N2, NO, NO2, etc.) during the pyrolysis of NH4NO3 can play a templating role in thermal condensation of melamine. The optical properties of the CNx samples were characterized with UV–vis and PL spectra and displayed in Fig. 2. As shown in Fig. 2a, samples BCN and CN15 displayed similar photoabsorpion from ultraviolet to visible light, and their band gaps are both at 2.75 eV. The photoluminescence spectrum emission arises from the recombination of photogenerated electron-hole pairs, and is therefore useful to probe the transfer and recombination processes of these photogenerated carriers [14,15]. As shown in Fig. 2b, the strong photoluminescence of sample BCN is greatly reduced in the CN15 sample, suggesting that the Table 1 Properties of BCN and CN15. Sample
Molar ratio of C/ Na
SBET (m2/ g)b
Vpore (cm3/ g)c
Band Energy (eV)d
BCN CN5 CN15 CN25 CN50 CN100 CN200
0.670 / 0.673 / / / /
15.1 12.9 24.4 24.3 23.6 24.5 14.3
0.03 0.04 0.05 0.06 0.07 0.06 0.03
2.75 2.74 2.75 2.75 2.73 2.75 2.75
a b c d
4. Conclusions Graphitic carbon nitride was prepared from the pyrolysis of melamine with the assistance of NH4NO3. This procedure increased the mesoporous surface area, enhanced the absorption of visible light, improved the electron-hole separation efficiency, and promoted the photocatalytic performance. CNx samples demonstrated more rapid RhB photodegradation than the BCN sample prepared without NH4NO3 assistance. The mass ratio of NH4NO3/melamine of 0.15
The average value of two individual measurements by element analysis, Calculated by BET method. Calculated at P/P0 =0.95. Measured by UV–vis spectra.
2
Materials Letters xx (xxxx) xxxx–xxxx
L. Luo et al.
(a)
0.4
6
Eg=2.75 eV
4
Eg=2.75 eV
2 0
2.25 2.50 2.75 3.00
hv (eV)
0.2
BCN CN15
0.0 300
400 500 600 700 Wavelength (nm)
(b)
Intensity (a.u.)
0.6
(Ahv)
Absorbance (a.u.)
0.8
800
BCN CN15
400
450 500 550 Wavelength (nm)
600
Fig. 2. (a) UV–vis and (b) PL spectra of BCN and CN15. The inset of Fig. 3a shows the optical bandgap determination from the Tauc plots.
100
BCN CN5 CN15 CN25 CN50 CN100 CN200
60 40 20
3
Ln(C/C0)
RhB (C/C0)
80
BCN CN5 CN15 CN25 CN50 CN100 CN200
4
(a)
2
(b)
1 0
0 0
10
20
30
40
50
0
60
10 20 30 40 50 60 Reaction Time (min)
Reaction Time (min) 100
(c)
1st
0.10
0.05
2nd
3rd
4th
5th
(d)
80
RhB (C/C0)
-1
K (min )
0.15
60 40 20 0
0.00
0.0 0.5 1.0 1.5 2.0 Ratio of NH4NO3/Melamine
0 15 0 15 0 15 0 15 0 15
Reaction Time (min)
Fig. 3. (a) Photocatalytic degradation of RhB as a function of reaction time, (b) first-order kinetics plot and (c) the kinetic constants of RhB degradation in the presence of NH4NO3 assisted g-C3N4, (d) repeatability of RhB degradation catalysis by CN15.
References
shows the highest catalytic activity with a kinetic constant of 0.167 min−1 that is 4.5 times as high as that on BCN. The synthesis strategy involving NH4NO3-assisted preparation of g-C3N4 is a facile, repeatable, environmentally friendly and efficient way to prepare gC3N4 with a high photocatalytic performance.
[1] X. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J.M. Carlsson, K. Domen, M. Antonietti, A metal-free polymeric photocatalyst for hydrogen production from water under visible light, Nat. Mater. 8 (2009) 76–80. [2] J. Zhang, F. Guo, X. Wang, An optimized and general synthetic strategy for fabrication of polymeric carbon nitride nanoarchitectures, Adv. Funct. Mater. 23 (2013) 3008. [3] Y. Wang, F. Wang, Y. Zuo, X. Zhang, L.-F. Cui, Simple synthesis of ordered cubic mesoporous graphitic carbon nitride by chemical vapor deposition method using melamine, Mater. Lett. 136 (2014) 271. [4] S. Cao, J. Low, J. Yu, M. Jaroniec, Polymeric photocatalysts based on graphitic carbon nitride, Adv. Mater. 27 (2015) 2150–2176. [5] Y. Zheng, L. Lin, B. Wang, X. Wang, Graphitic carbon nitride polymers toward sustainable photoredox catalysis, Angew. Chem. Int. Ed. 54 (2015) 12868–12884. [6] F. Cheng, J. Yan, C. Zhou, B. Chen, P. Li, Z. Chen, X. Dong, An alkali treating strategy for the colloidization of graphitic carbon nitride and its excellent photocatalytic performance, J. Colloid Interface Sci. 468 (2016) 103. [7] S. Yang, Y. Gong, J. Zhang, L. Zhan, L. Ma, Z. Fang, R. Vajtai, X. Wang, P.M. Ajayan, Exfoliated graphitic carbon nitride nanosheets as efficient catalysts for hydrogen evolution under visible light, Adv. Mater. 25 (2013) 2452–2456. [8] X. Zhang, X. Xie, H. Wang, J. Zhang, B. Pan, Y. Xie, Enhanced photoresponsive ultrathin graphitic-phase C3N4 nanosheets for bioimaging, J. Am. Chem. Soc. 135 (2013) 18–21.
Acknowledgements This work was supported by State Key Program of National Natural Science Foundation of China (Grant no. 21236008, 21306018), and Fundamental Research Funds for the Central Universities (Grant no. DUT16LK12).
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at doi:10.1016/j.matlet.2016.11.043. 3
Materials Letters xx (xxxx) xxxx–xxxx
L. Luo et al.
efficient heterogeneous photocatalysis, J. Mater. Chem. A 1 (2013) 14766. [14] L. Shi, L. Liang, F. Wang, M. Liu, K. Chen, K. Sun, N. Zhang, J. Sun, Higher yield urea-derived polymeric graphitic carbon nitride with mesoporous structure and superior visible-light-responsive activity, ACS Sustain. Chem. Eng. 3 (2015) 3412–3419. [15] X. Bai, L. Wang, Y. Wang, W. Yao, Y. Zhu, Enhanced oxidation ability of g-C3N4 photocatalyst via C60 modification, applied, Catal. B: Environ., 152- 153 (2014) 262–270. [16] Z. Wang, W. Guan, Y. Sun, F. Dong, Y. Zhou, W.K. Ho, Water-assisted production of honeycomb-like g-C3N4 with ultralong carrier lifetime and outstanding photocatalytic activity, Nanoscale 7 (2015) 2471–2479.
[9] X. Zhang, X. Xie, H. Wang, J. Zhang, B. Pan, Y. Xie, Enhanced photoresponsive ultrathin graphitic-phase C3N4 nanosheets for bioimaging, J. Am. Chem. Soc. 135 (2012) 18. [10] F. Cheng, H. Wang, X. Dong, The amphoteric properties of g-C3N4 nanosheets and fabrication of their relevant heterostructure photocatalysts by an electrostatic reassembly route, Chem. Commun. 51 (2015) 7176. [11] P. Niu, L. Zhang, G. Liu, H.-M. Cheng, Graphene-like carbon nitride nanosheets for improved photocatalytic activities, Adv. Funct. Mater. 22 (2012) 4763–4770. [12] X. Dong, F. Cheng, Recent development in exfoliated two-dimensional g-C3N4 nanosheets for photocatalytic applications, J. Mater. Chem. A 3 (2015) 23642. [13] J. Xu, L. Zhang, R. Shi, Y. Zhu, Chemical exfoliation of graphitic carbon nitride for
4
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Inorganic salt-assisted fabrication of graphitic carbon nitride with enhanced photocatalytic degradation of Rhodamine B ⁎
Lei Luoa, Anfeng Zhanga, Michael J. Janikb, Keyan Lia, Chunshan Songa,b, , Xinwen Guoa,
⁎
a State Key Laboratory of Fine Chemicals, PSU-DUT Joint Center for Energy Research, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China b EMS Energy Institute, PSU-DUT Joint Center for Energy Research and Department of Energy & Mineral Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
A R T I C L E I N F O
A BS T RAC T
Keywords: Porous materials Semiconductors Carbon materials
With the assistance of inorganic salt, graphitic carbon nitride nanosheets were prepared with increased mesoporous surface area for promoting the photocatalytic performance compared with the one without. Series of photocatalysts with different mass ratio of NH4NO3/melamine were prepared and characterized by XRD, FTIR, XPS, TEM, SEM, N2 physical adsorption, UV–vis and PL spectrometries. Photocatalytic degradation of RhB under visible light irradiation (λ > 420 nm) was applied to evaluate catalytic properties. The catalytic activity maximizes at an intermediate NH4NO3/melamine ratio at 0.15, giving a maximum performance, RhB totally being degraded within 30 min and kinetic constant reaching 0.167 min−1 that is 4.5 times as high as that on BCN. The NH4NO3 assisted procedure is a facile, repeatable, environmental friendly, and efficient method for preparing g-C3N4 nanosheets with high photocatalytic performance.
1. Introduction
C3N4 photocatalytic activity.
Graphitic carbon nitride (g-C3N4) is a promising metal-free visible light photocatalyst [1–3]. However, the photocatalytic activity of the pristine g-C3N4 is low due to its limited specific surface area, fast rate of charge recombination, and low electronic conductivity [4–6]. Hardtemplating method is a controllable, flexible and precise strategy for introducing a nanostructure, but the usage of hazardous fluoridecontained reagents (HF, NH4HF2) to remove the template as well as multiple step procedures with long operation periods limit its practical application. In contrast, top-down approaches such as liquid exfoliation [7–10] or thermal exfoliation [11–13] are utilized successfully to break the stacking system of bulk g-C3N4 to nanosheets and increase its photocatalytic activity. Though exfoliated nanosheets exhibit promoted photocatalytic activity with enhanced photoabsorption and photoresponse [8], their yield is still lower than 40% [5]. It would be advantageous to prepare g-C3N4 from one single step, with shorter preparation time, and with enhanced photocatalytic activity. In this work, g-C3N4 was synthesized by the thermal condensation of melamine, with the assistance of NH4NO3, to increase the specific mesoporous surface area, enhance the charge separation efficiency, and promote the photocatalytic performance. Photocatalytic degradation of RhB under visible light irradiation was performed to evaluate the g-
2. Experimental
⁎
Graphitic carbon nitride was synthesized from the thermal condensation of melamine with or without the assistance of NH4NO3. In a typical synthesis procedure, 3.0 g melamine precursor was mixed with a specified amount of NH4NO3 then ground to a fine powder. The powder was placed into a 30 mL covered crucible and heated in static air to 550 °C at a heating rate of 10 °C/min. After cooling, the obtained yellow product was ground for further characterization or evaluation. Samples are denoted as CNx where x/100 represents the mass ratio of NH4NO3/melamine. For sample CN15, the mass ratio of NH4NO3/ Melamine is 0.15. Bulk carbon nitride (BCN) was prepared without NH4NO3. The relevant characterization and evaluation can be found in Electronic Supplementary Information. 3. Results and discussion The crystal structure of the as-prepared samples BCN and CN15 were characterized with XRD, FT-IR, and XPS spectra, which together demonstrated the characteristic structure of g-C3N4 (shown in Fig. S1). The morphologies of the as-prepared catalysts were investigated with
Corresponding authors. E-mail address: [email protected] (X. Guo).
http://dx.doi.org/10.1016/j.matlet.2016.11.043 Received 20 September 2016; Received in revised form 8 November 2016; Accepted 9 November 2016 Available online xxxx 0167-577X/ © 2016 Elsevier B.V. All rights reserved.
Please cite this article as: Luo, L., Materials Letters (2016), http://dx.doi.org/10.1016/j.matlet.2016.11.043
Materials Letters xx (xxxx) xxxx–xxxx
L. Luo et al.
(b)
(a)
(c)
500 nm
4μm
(e)
(d)
500 nm
(f)
500 nm
200 nm
200 nm
Fig. 1. SEM (a) and TEM (d) images of BCN, SEM images of CN15 (b and c), TEM images of sample CN15 (e and f).
energy-wasting carrier recombination will be suppressed. The improved charge separation efficiency can be attributed to the pore structure and increased surface area that facilitates the transfer and separation of photogenerated charge carriers, prolongs their lifetime, and thus lowers the PL intensity [16]. The enhanced electron-hole separation efficiency may lead to improved photocatalytic quantum efficiency and activity. The photocatalytic degradation of RhB under visible light irradiation was applied as a probe reaction to evaluate the photocatalytic activity of the CNx samples. The amount of RhB adsorbed to the g-C3N4 before light irradiation was less than 20% for all CNx samples. As shown in Fig. 3a, RhB is degraded in the presence of each photocatalyst, however, the photocatalytic activity of all CNx samples exceeds BCN. The kinetic constants over the different photocatalysts are presented in Fig. 3b and c. BCN presents the lowest rate constant of k=0.037 min−1, and k increased significantly as the mass ratio of NH4NO3 increased. The kinetic constant reaches a maximum for CN15 at k=0.167 min−1. Further increasing the mass ratio of NH4NO3 led to a decrease of the kinetic constant. The enhanced photocatalytic activity arises from both an increase in surface area and increased electron-hole separation efficiency, as evidenced by the PL spectra. The increased specific surface area of the nanosheets can not only increase the active site, but also shorten the distance photogenerated electron-hole pairs migrate to reach the organic pollutant at the surface with the strong oxidative hole. For sample CN15, the reusability was also investigated by five consecutive reactivity studies (Fig. 3d). As the irradiation time was prolonged, RhB degraded without evident deactivation, which indicates stability of the CN15 photocatalyst.
TEM, SEM and nitrogen physical adsorption. Fig. 1 shows SEM and TEM images of the as-prepared sample BCN and CN15. The BCN sample is dense with a large particle size, whereas CN15 appears as a loose and soft material. The TEM images of CN15 show ultrathin nanosheets. By introducing NH4NO3, the layers of bulk g-C3N4 are separated, modifying the nanostructure. Nitrogen physical adsorption further supports the result obtained from SEM and TEM and adds quantitative analysis on the pore and textural properties. The adsorption-desorption isotherms are shown in Fig. S2, with textural properties presented in Table 1. By introducing NH4NO3, the SBET of CN15 is much higher than that of pristine BCN, suggesting that the gas products (N2, NO, NO2, etc.) during the pyrolysis of NH4NO3 can play a templating role in thermal condensation of melamine. The optical properties of the CNx samples were characterized with UV–vis and PL spectra and displayed in Fig. 2. As shown in Fig. 2a, samples BCN and CN15 displayed similar photoabsorpion from ultraviolet to visible light, and their band gaps are both at 2.75 eV. The photoluminescence spectrum emission arises from the recombination of photogenerated electron-hole pairs, and is therefore useful to probe the transfer and recombination processes of these photogenerated carriers [14,15]. As shown in Fig. 2b, the strong photoluminescence of sample BCN is greatly reduced in the CN15 sample, suggesting that the Table 1 Properties of BCN and CN15. Sample
Molar ratio of C/ Na
SBET (m2/ g)b
Vpore (cm3/ g)c
Band Energy (eV)d
BCN CN5 CN15 CN25 CN50 CN100 CN200
0.670 / 0.673 / / / /
15.1 12.9 24.4 24.3 23.6 24.5 14.3
0.03 0.04 0.05 0.06 0.07 0.06 0.03
2.75 2.74 2.75 2.75 2.73 2.75 2.75
a b c d
4. Conclusions Graphitic carbon nitride was prepared from the pyrolysis of melamine with the assistance of NH4NO3. This procedure increased the mesoporous surface area, enhanced the absorption of visible light, improved the electron-hole separation efficiency, and promoted the photocatalytic performance. CNx samples demonstrated more rapid RhB photodegradation than the BCN sample prepared without NH4NO3 assistance. The mass ratio of NH4NO3/melamine of 0.15
The average value of two individual measurements by element analysis, Calculated by BET method. Calculated at P/P0 =0.95. Measured by UV–vis spectra.
2
Materials Letters xx (xxxx) xxxx–xxxx
L. Luo et al.
(a)
0.4
6
Eg=2.75 eV
4
Eg=2.75 eV
2 0
2.25 2.50 2.75 3.00
hv (eV)
0.2
BCN CN15
0.0 300
400 500 600 700 Wavelength (nm)
(b)
Intensity (a.u.)
0.6
(Ahv)
Absorbance (a.u.)
0.8
800
BCN CN15
400
450 500 550 Wavelength (nm)
600
Fig. 2. (a) UV–vis and (b) PL spectra of BCN and CN15. The inset of Fig. 3a shows the optical bandgap determination from the Tauc plots.
100
BCN CN5 CN15 CN25 CN50 CN100 CN200
60 40 20
3
Ln(C/C0)
RhB (C/C0)
80
BCN CN5 CN15 CN25 CN50 CN100 CN200
4
(a)
2
(b)
1 0
0 0
10
20
30
40
50
0
60
10 20 30 40 50 60 Reaction Time (min)
Reaction Time (min) 100
(c)
1st
0.10
0.05
2nd
3rd
4th
5th
(d)
80
RhB (C/C0)
-1
K (min )
0.15
60 40 20 0
0.00
0.0 0.5 1.0 1.5 2.0 Ratio of NH4NO3/Melamine
0 15 0 15 0 15 0 15 0 15
Reaction Time (min)
Fig. 3. (a) Photocatalytic degradation of RhB as a function of reaction time, (b) first-order kinetics plot and (c) the kinetic constants of RhB degradation in the presence of NH4NO3 assisted g-C3N4, (d) repeatability of RhB degradation catalysis by CN15.
References
shows the highest catalytic activity with a kinetic constant of 0.167 min−1 that is 4.5 times as high as that on BCN. The synthesis strategy involving NH4NO3-assisted preparation of g-C3N4 is a facile, repeatable, environmentally friendly and efficient way to prepare gC3N4 with a high photocatalytic performance.
[1] X. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J.M. Carlsson, K. Domen, M. Antonietti, A metal-free polymeric photocatalyst for hydrogen production from water under visible light, Nat. Mater. 8 (2009) 76–80. [2] J. Zhang, F. Guo, X. Wang, An optimized and general synthetic strategy for fabrication of polymeric carbon nitride nanoarchitectures, Adv. Funct. Mater. 23 (2013) 3008. [3] Y. Wang, F. Wang, Y. Zuo, X. Zhang, L.-F. Cui, Simple synthesis of ordered cubic mesoporous graphitic carbon nitride by chemical vapor deposition method using melamine, Mater. Lett. 136 (2014) 271. [4] S. Cao, J. Low, J. Yu, M. Jaroniec, Polymeric photocatalysts based on graphitic carbon nitride, Adv. Mater. 27 (2015) 2150–2176. [5] Y. Zheng, L. Lin, B. Wang, X. Wang, Graphitic carbon nitride polymers toward sustainable photoredox catalysis, Angew. Chem. Int. Ed. 54 (2015) 12868–12884. [6] F. Cheng, J. Yan, C. Zhou, B. Chen, P. Li, Z. Chen, X. Dong, An alkali treating strategy for the colloidization of graphitic carbon nitride and its excellent photocatalytic performance, J. Colloid Interface Sci. 468 (2016) 103. [7] S. Yang, Y. Gong, J. Zhang, L. Zhan, L. Ma, Z. Fang, R. Vajtai, X. Wang, P.M. Ajayan, Exfoliated graphitic carbon nitride nanosheets as efficient catalysts for hydrogen evolution under visible light, Adv. Mater. 25 (2013) 2452–2456. [8] X. Zhang, X. Xie, H. Wang, J. Zhang, B. Pan, Y. Xie, Enhanced photoresponsive ultrathin graphitic-phase C3N4 nanosheets for bioimaging, J. Am. Chem. Soc. 135 (2013) 18–21.
Acknowledgements This work was supported by State Key Program of National Natural Science Foundation of China (Grant no. 21236008, 21306018), and Fundamental Research Funds for the Central Universities (Grant no. DUT16LK12).
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at doi:10.1016/j.matlet.2016.11.043. 3
Materials Letters xx (xxxx) xxxx–xxxx
L. Luo et al.
efficient heterogeneous photocatalysis, J. Mater. Chem. A 1 (2013) 14766. [14] L. Shi, L. Liang, F. Wang, M. Liu, K. Chen, K. Sun, N. Zhang, J. Sun, Higher yield urea-derived polymeric graphitic carbon nitride with mesoporous structure and superior visible-light-responsive activity, ACS Sustain. Chem. Eng. 3 (2015) 3412–3419. [15] X. Bai, L. Wang, Y. Wang, W. Yao, Y. Zhu, Enhanced oxidation ability of g-C3N4 photocatalyst via C60 modification, applied, Catal. B: Environ., 152- 153 (2014) 262–270. [16] Z. Wang, W. Guan, Y. Sun, F. Dong, Y. Zhou, W.K. Ho, Water-assisted production of honeycomb-like g-C3N4 with ultralong carrier lifetime and outstanding photocatalytic activity, Nanoscale 7 (2015) 2471–2479.
[9] X. Zhang, X. Xie, H. Wang, J. Zhang, B. Pan, Y. Xie, Enhanced photoresponsive ultrathin graphitic-phase C3N4 nanosheets for bioimaging, J. Am. Chem. Soc. 135 (2012) 18. [10] F. Cheng, H. Wang, X. Dong, The amphoteric properties of g-C3N4 nanosheets and fabrication of their relevant heterostructure photocatalysts by an electrostatic reassembly route, Chem. Commun. 51 (2015) 7176. [11] P. Niu, L. Zhang, G. Liu, H.-M. Cheng, Graphene-like carbon nitride nanosheets for improved photocatalytic activities, Adv. Funct. Mater. 22 (2012) 4763–4770. [12] X. Dong, F. Cheng, Recent development in exfoliated two-dimensional g-C3N4 nanosheets for photocatalytic applications, J. Mater. Chem. A 3 (2015) 23642. [13] J. Xu, L. Zhang, R. Shi, Y. Zhu, Chemical exfoliation of graphitic carbon nitride for
4