- Email: [email protected]
Simple synthesis of oxygen functional layered carbon nitride with near-infrared light photocatalytic activity
Accepted Manuscript Simple synthesis of oxygen functional layered carbon nitride with near-infrared light photocatalytic activity
Xue Liu, Xiaoli Wu, Jing Li, Lingyan Liu, Yongqiang Ma PII: DOI: Reference:
S1566-7367(16)30446-0 doi: 10.1016/j.catcom.2016.12.001 CATCOM 4870
To appear in:
Catalysis Communications
Received date: Revised date: Accepted date:
22 September 2016 1 November 2016 2 December 2016
Please cite this article as: Xue Liu, Xiaoli Wu, Jing Li, Lingyan Liu, Yongqiang Ma , Simple synthesis of oxygen functional layered carbon nitride with near-infrared light photocatalytic activity. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Catcom(2016), doi: 10.1016/ j.catcom.2016.12.001
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Simple synthesis of oxygen functional layered carbon nitride with near-infrared light photocatalytic activity Xue Liua, Xiaoli Wua, Jing Lib, Lingyan Liub, Yongqiang Maa,∗
a
Department of Applied Chemistry, College of Science, China Agricultural University, Beijing
RI
b
PT
100193, China
State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071,
author.
NU
∗ Corresponding
SC
China
MA
E-mail address: [email protected] (Y. Ma)
Keywords: Carbon nitride; Oxygen functional; Near-infrared light; Photocatalysis
D
ABSTRACT: Oxygen functional carbon nitride (NOCN) was synthesized via a moderate
PT E
ultrasonic-assisted method. With highly ordered layered structure and poriferous morphology simultaneously, NOCN was proven to be a new near-infrared light responsive photocatalyst.
CE
Electronic structure was tuned for the intervention of oxygen, which further changed its light
AC
response characters. Different from the previous reported NIR-driven photocatalyst, metal elements were not involved in this material.
1
ACCEPTED MANUSCRIPT 1.
Introduction
As the most promising renewable energy source, solar energy is considered to be one of the major choices in tackling global energy shortage and pollution issues. Extensive research has been conducted in light harvesting materials [1,2]. Considering the solar spectral composition,
PT
photocatalysts that are effective under visible light have attracted more attention in the recent
RI
years [3]. Typically, graphitic carbon nitride (GCN) as a novel “metal-free” semiconductor has
SC
aroused great interest since the pioneering work in 2009 [4]. It has been widespread utilized in versatile redox reactions, bioimaging and material science. GCN is found to show an intrinsic
NU
absorption in the visible region [5-7].Dye sensitization, doping, nanostructure design,
MA
morphological engineering and heterostructure construction are the common strategies to improve the visible light absorption of carbon nitride based materials [8-11]. However, every
PT E
D
step forward in utilizing the solar light is seemingly confined in the short wavelength range.
CE
Near-infrared light, which occupied almost equal proportion of visible light in sunlight, remains underutilized for photocatalysis. Hitherto, two major types of near-infrared light
AC
photocatalysts have been reported, up-conversion photocatalysts and NIR-active photocatalysts. In the former, NIR light is absorbed and converted to UV light by rare earth ions doped fluoride crystals [12] or carbon quantum dots (CQDs) [13] and utilized by TiO2 indirectly. Besides, few NIR-driven photocatalysts, such as Cu2(OH)PO4, Bi2WO6 and Ag/Ag2O heterostructures, etc. have been reported the ability in directly utilizing NIR light recently
2
ACCEPTED MANUSCRIPT [14-16]. Thus, seeking more photocatalysts to achieve the deep exploitation and utilization of solar spectrum in near-infrared part is significative.
Here we demonstrate that oxygen functional layered carbon nitride not only exhibits a much enhanced visible light absorption capability, but also possesses activity under
PT
direct NIR lighting. It is efficient for degradation of Rhodamine B (RhB) in aqueous
RI
solution under NIR light irradiation (λ>800 nm). Nitric acid (HNO 3)-assisted treatment
SC
allows a gentle way to achieve oxygen involved and the fabrication of orderly layered
NU
cancellous structure, which increase significantly the degradation efficiency. Different from the previous reported NIR-driven photocatalyst, metal elements are not involved in
MA
the process. This ensures a more economically feasible and environmentally friendly
Experimental
PT E
2.
D
scheme for near-infrared light hunting.
CE
Bulk carbon nitride (BCN) was obtained from the thermal condensation of urea. Aqueous
AC
HNO3 (2 mol/L) was selected as the oxidant and dispersion medium in ultrasonic process (the aqueous HNO3 treated sample was denoted as NOCN). Photocatalytic degradation of Rhodamine B (RhB) was investigated under near-infrared light (>800 nm) irradiation. The detailed experimental procedures see Supplementary material.
3.
Results and discussion
3
ACCEPTED MANUSCRIPT Elemental analysis (EA) of the NOCN (C/O ratio of 6.9:1) and BCN (C/O ratio of 21.4:1) suggest that oxygen atoms have been introduced during the HNO3 treated process (Table S1). The survey X-ray photoelectron spectroscopy (XPS) spectrum (Fig. 1a) reveals that
PT
the two samples are both mainly composed of C, N and O elements. And more
RI
remarkable, O element increases significantly in NOCN sample, which is consistent
SC
with the results of EA. The chemical bonding between the carbon and nitrogen atoms was futher investigated by high-resolution XPS spectra of C 1s and N 1s spectrum. In C
NU
1s spectrum (Fig. S1a), peaks at 285.1, 288.2 and 289.2 eV are correspond to C-C,
MA
C-N-C coordination, and a trace amount of C-O bonding, respectively [17]. The C1s spectra of the NOCN sample shows enhanced intensity of the peak at 289.2 eV, which
D
derived from C-O bonding also supports the introduction of O atoms, instead of simple
PT E
absorption [18]. Three main binding energies can be separated in the N 1s spectrum 2
(Fig. S1b). Peaks at 398.8, 399.7, 400.7 and 404.4 eV correspond to sp C−N−C 3
CE
bonds, sp H−N−[C]3, C−NHx (amino functional groups) and π excitations [19]. The
AC
weak peak at 404.4 eV almost disappears in the N 1s XPS spectra of NOCN sample. It confirms that the states of delocalized π electrons are affected by the containing oxygen [20], which may influence the surface active sites. The enhancement and peak shift (from 531.8 to 532.2 eV) in the deconvolution of O1s XPS (Fig. S1c) further confirms the oxygen-containing functional groups in NOCN sample [21,22].
4
ACCEPTED MANUSCRIPT As shown in the FT-IR spectrum (Fig. S2), the overall absorbance band intensity of -1
NOCN is stronger than that of BCN. The peaks at 3351, 1705, 1300 and 980 cm , correspond to O-H bonds, C=O bonds, C-O bonds and C-O-C bonds, respectively, which also support the introduction of oxygen atoms [23]. Furthermore, red shift of
RI
PT
absorption peaks of NOCN sample, on account of the change of conjugated structure.
SC
X-ray diffraction (XRD) patterns (Fig. 1b) of the two samples reveal two characteristic peaks located at 2θ=13.0 and 27.4°, corresponding to the in-plane repeating of
NU
tri-s-triazine units and the inter-layer graphite stacking, respectively [24]. Generally,
MA
treated with strong oxidants (such as KMnO 4, concentrated HNO 3 and H2SO4) may induce the damage of the structure order degree [25]. However, after aqueous HNO3
D
treated, the XRD intensity of NOCN significantly enhances, which implying the in-plane
PT E
structure remains untouched. It seems to be a rational explanation to an increased crystallinity of NOCN, especially through the stackig dimension [26]. The interlayer
CE
structure of NOCN sample becomes so much more organized and less
AC
amorphous—than it used to be. Concurrent with the generation of cancellous structure, the long-range ordered interlayer periodic stacking of NOCN has been formed [27]. With the use of the interlayer galleries as diffusion channels, such an orderly layered structure has been proven facilitative for light absorption [28,29].
Without aqueous HNO3 treated in the synthesis process, the morphology of BCN reveals a featureless packed structure (Fig. S3a & b). The overly dense of structural 5
ACCEPTED MANUSCRIPT stacking may block the travel of photon-generated electrons. By contrast, the transmission electron microscopy (TEM) images of NOCN (Fig. S3c & d) display sequential layer structure with numerous in-plane pores, which is analogous to the bone matrix with osteoporosis. These interlaced pores could increase reactive sites and
PT
accelerate the diffusion of photoinduced charge carriers [30]. In this case,
RI
photon-generated electrons could transfer freely throughout the interlamination with
SC
assistance from the enormous pores. The BET surface area of NOCN increases overtly 2 -1
from 48.48 to107.93 m g , 2.2 times as high as that of the BCN. NOCN also possesses
NU
enlarged pore volume (Table S2). This specific structure ensures greater mobility of
MA
photoelectrons.
D
Previous study suggested that GCN is a good visible light active photocatalyst.
PT E
NOCN demonstrates an extended range of light absorption in 300-800 nm (Fig. S4). In addition, the UV/Vis/NIR absorption spectrum of the samples derived from its diffuse
CE
reflectance spectrum (DRS) is shown in Fig. 2. The GCN sample reveals negligible
AC
absorption in the NIR region. Strikingly, the NOCN sample induces an expanded optical absorption beyond 1500 nm, which belongs long-wavelength near-infrared light.
The ability for utilizing of NIR light is confirmed by the photocatalytic degradation for RhB under NIR irradiation (>800nm) (Fig. S5). The degradation rate of RhB for NOCN is over 30% (3h). The circulating water was used to maintain the temperature of RhB solution at 30 °C during extended NIR irradiation. Therefore, the thermocatalytic 6
ACCEPTED MANUSCRIPT reference experiment at 30 °C in the dark was carried out. Thus it can be concluded that the decrement of RhB (about 10%) is resulted from the temperature effect other than BCN sample. Long periods experiment further confirmes that the degradation of RhB resulted from the near-infrared photocatalytic property of NOCN instead of
PT
thermolysis or self-decomposition (Fig. 3a). The renewable catalytic activity of NOCN
RI
photocatalysts was investigated. After four cycles (total duration 96 hours), there is no
SC
obvious decrease in photocatalytic degradation activity (Fig. 3b), suggesting the
NU
superior stable of the NOCN sample.
MA
To study the reaction mechanisms of NOCN photocatalyst, hydroxyl free radical (•OH), hole 2−
+
(h ), and superoxide radical (•O ), as the proposed reactive oxidative species, were evaluated -1
D
using corresponding scavengers. In our experiments, 0.6 mmol L TBA, EDTA and BQ were 2−
+
PT E
used to remove •OH, h , and •O , respectively [31]. The results are shown in Fig. S6. It is +
clear that h , •OH, and •O
2−
+
work in concert to inhibit the photocatalytic activity of NOCN. The 2−
CE
influencing degree is h > •OH > •O .
AC
Albeit the NOCN sample possesses a larger surface area, we speculate that the participation of oxygen is the predominant factor for the conspicuous long-wavelength NIR response. With the accession of oxygen, the electronic structure may be tuned. Thus, we predict four different oxygen-containing structures and calculate the bandgap of GCN unit between HOMO and LUMO (Fig. 4). The results gleaned suggest that structural unit Ⅲ (a downshift by 0.11 eV) and unit Ⅳ (a downshift by 0.26 eV), which with a narrow bandgap are favorably occurred after oxygen inbreak. As known, the heteroatoms with higher periodic 7
ACCEPTED MANUSCRIPT elements could narrow the band gaps of conjugated polymers [32]. Thus, with partial defect of tri-s-triazine aromatic rings, the NOCN in essence reduce the band gap and exploit triumphantly in the near-infrared region. Conclusions
PT
4.
To summarize, oxygen functional layered carbon nitride is proved actived under
RI
near-infrared light in this study. Aqueous HNO 3 assistant-oxygen intervention and the
SC
cancellous structure with high crystalline can significantly improve the
NU
photodegradation efficiency under NIR irradiation. Moderate oxygen intervene has been considered the predominant factor for the conspicuous photoinduced property.
MA
This simple non-metallic material has demonstrated new possibilities of using
PT E
Acknowledgements
D
long-wavelength near-infrared light.
CE
This work was supported by Ministry of Science and Technology of the People’s
AC
Republic of China (2015BAK45B01).
8
ACCEPTED MANUSCRIPT References [1]
A. Fujishima, K. Honda, Nature 238 (1972) 37-38.
[2]
K. Park, Q. F. Zhang, B. B. Garcia, X. Y. Zhou, Y. H. Jeong, G. Z. Cao, Adv. Mater. 22 (2010) 2329-2332. G. Aragay, F. Pino, A. Merkoci, Chem. Rev. 112 (2012) 5317-5338.
[4]
X. C. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J. M. Carlsson, K.
[5]
SC
Domen, M. Antonietti, Nat. Mater. 8 (2009) 76-80.
RI
PT
[3]
Y. Zheng, L. H. Lin, B. Wang, X. C. Wang, Angew. Chem. Int. Ed. 54 (2015) 12868
NU
–12884.
J. S. Zhang, Y. Chen, X. C. Wang, Energy Environ. Sci. 8 (2015) 3092-3108.
[7]
M. K. Bhunia, K. Yamauchi, K. Takanabe, Angew. Chem. Int. Ed. 53 (2014) 11001
MA
[6]
Gu. G. Zhang, S. H. Zang, L. H. Lin, Z. A. Lan, G. S. Li, X. C. Wang, ACS Appl.
PT E
[8]
D
–11005.
Mater. Interfaces 8 (2016) 2287−2296. M. Shalom, S. Inal, C. Fettkenhauer, D. Neher, M. Antonietti, J. Am. Chem. Soc.
CE
[9]
135 (2013) 7118−7121. D. D. Zheng, X. N. Cao, X. C. Wang, Angew. Chem. Int. Ed. 55 (2016) 11512
AC
[10]
–12516. [11]
X. Y. Xia, N. Deng, G. W. Cui, J. F. Xie, X. F. Shi, Y. Q. Zhao, Q. Wang, W. Wang, B. Tang, Chem. Commun. 51 (2015) 10899-10902.
[12]
W. Qin, D. Zhang, D. Zhao, L. Wang, K. Zheng, Chem. Commun. 46 (2010) 2304-2306. 9
ACCEPTED MANUSCRIPT [13]
H. T. Li, R. H. Liu, Y. Liu, H. Huang, H. Yu, H. Ming, S. Y. Lian, S. T. Lee, Z. H. Kang, J. Mater. Chem. 22 (2012) 17470-17475.
[14]
G. Wang, B. B. Huang, X. C. Ma, Z. Y. Wang, X. Y. Qin, X. Y. Zhang, Y. Dai, M. H. Whangbo, Angew. Chem. Int. Ed. 52 (2013) 4810-4813. J. Tian, Y. H. Sang, G. W. Yu, H. D. Jiang, X. N. Mu, H. Liu, Adv. Mater. 25 (2013)
PT
[15]
RI
5075-5080.
H. R. Yang, J. Tian, T. Li, H. Z. Cui, Catal. Commun. 87 (2016) 82–85.
[17]
D. J. Martin, K. P. Qiu, S. A. Shevlin, A. D. Handoko, X. W. Chen, Z. X. Guo, J. W.
SC
[16]
J. Han, L. L. Zhang, S. Lee, J. Oh, K. Lee, J. R. Potts, J. Ji, X. Zhao, R. S. Ruoff, S.
MA
[18]
NU
Tang, Angew. Chem. Int. Ed. 53 (2014) 9240-9245.
Park, ACS Nano 7 (2013) 19-26.
Q. H. Liang, Z. Li, X. L. Yu, Z. H. Huang, F. Y. Kang, Q. H. Yang, Adv. Mater. 27
[20]
PT E
(2015) 4634-4639.
D
[19]
D. H. Deng, K. S. Novoselov, Q. Fu, N. F. Zheng, Z. Q. Tian, X. H. Bao, Nat.
S. N. Guo, Y. Zhu, Y. Y. Yan, Y. L. Min, J. C. Fan, Q. J. Xu, Appl. Catal. B 185
AC
[21]
CE
Nanotechnol. 11 (2016) 218-230.
(2016) 315–321. [22]
H. Wang, S. L. Jiang, S. C. Chen, D. D. Li, X. D. Zhang, W. Shao, X. S. Sun, J. F. Xie, Z. Zhao, Q. Zhang, Y. P. Tian, Y. Xie, Adv. Mater. 28 (2016) 6940–6945.
[23]
T. Yeh, J. Syu, C. Cheng, T. Chang, H. Teng, Adv. Funct. Mater. 20 (2010) 2255 –2262.
10
ACCEPTED MANUSCRIPT [24]
S. B. Yang, Y. J. Gong, J. S. Zhang, L. Zhan, L. L. Ma, Z. Y. Fang, R. Vajtai, X. C. Wang, P. M. Ajayan, Adv. Mater. 25 (2013) 2452-2456.
[25]
J. Oh, R. J. Yoo, S. Y. Kim, Y. J. Lee, D. W. Kim, S. Park, Chem. Eur. J. 21 (2015) 6241-6246. M. J. Bojdys, J. O. Muller, M. Antonietti, A. Thomas, Chem. Eur. J. 14 (2008)
PT
[26]
Y. Y. Kang, Y. Q. Yang, L. C. Yin, X. D. Kang, G. Liu, H. M. Cheng, Adv. Mater. 27
SC
[27]
RI
8177–8182.
(2015) 4572-4577.
A. Mukherji, R. Marschall, A. Tanksale, C. H. Sun, S. C. Smith, G. Q. Lu, L. Z.
NU
[28]
[29]
MA
Wang, Adv. Funct. Mater. 21 (2011) 126-132.
Y. Y. Kang, Y. Q. Yang, L. C. Yin, X. D. Kang, L. Z. Wang, G. Liu, H. M. Cheng,
Z. F. Huang, J. J. Song, L. Pan, Z. M. Ziming, X. Q. Zhang, J. J. Zou, W. B. Mi, X.
PT E
[30]
D
Adv. Mater. 28 (2016) 6471-6477.
W. Zhang, L. Wang, Nano Energy 12 (2015) 646-656. S. F. Chen, Y. F. Hu, S. G. Meng, X. L. Fu, Appl. Catal. B 150–151 (2014) 564–
[32]
AC
573.
CE
[31]
X. G. Ma, Y. H. Lv, Jing Xu, Y. F. Liu, R. Q. Zhang, Y. F. Zhu, J. Phys. Chem. C 116 (2012) 23485-23493.
11
ACCEPTED MANUSCRIPT Figure captions:
Fig. 1 Chemical characterizations of the BCN and NOCN samples. (a) The survey XPS
PT
spectra; (b) XRD patterns.
SC
RI
Fig. 2 The experimental near-infrared absorption spectrum of BCN and NOCN samples.
Fig. 3 (a) Photocatalytic degradation of RhB over NOCN sample from photoctalytic
NU
decomposition (>800 nm), RhB photolysis without catalyst and thermal decomposition (30 °C)
MA
in the dark for long periods (24 h); (b) Cycling runs for the photocatalytic degradation of RhB in
D
the presence of NOCN under NIR light (>800 nm) irradiation.
PT E
Fig. 4 LUMO, HOMO, band gap variation value and schematic illustration of selected structural unit (tri-s-triazine structural unit (A) and structural units (Ⅰ-Ⅳ) with the intervention
AC
CE
of oxygen via a HNO3-assisted treatment).
12
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
Figure 1a
13
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
Figure 1b
14
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
Figure 2
15
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
Figure 3
16
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
Figure 4
17
ACCEPTED MANUSCRIPT Highlights
Oxygen carbon nitride was synthesized via a simple ultrasonic-assisted method.
Oxygen carbon nitride was proven to be a new near-infrared light responsive photocatalyst. Long-wavelength near-infrared light could be utilized without assist of metals.
The bandgap of oxygen carbon nitride unit between HOMO and LUMO were
PT
AC
CE
PT E
D
MA
NU
SC
RI
calculated.
18
Xue Liu, Xiaoli Wu, Jing Li, Lingyan Liu, Yongqiang Ma PII: DOI: Reference:
S1566-7367(16)30446-0 doi: 10.1016/j.catcom.2016.12.001 CATCOM 4870
To appear in:
Catalysis Communications
Received date: Revised date: Accepted date:
22 September 2016 1 November 2016 2 December 2016
Please cite this article as: Xue Liu, Xiaoli Wu, Jing Li, Lingyan Liu, Yongqiang Ma , Simple synthesis of oxygen functional layered carbon nitride with near-infrared light photocatalytic activity. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Catcom(2016), doi: 10.1016/ j.catcom.2016.12.001
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Simple synthesis of oxygen functional layered carbon nitride with near-infrared light photocatalytic activity Xue Liua, Xiaoli Wua, Jing Lib, Lingyan Liub, Yongqiang Maa,∗
a
Department of Applied Chemistry, College of Science, China Agricultural University, Beijing
RI
b
PT
100193, China
State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071,
author.
NU
∗ Corresponding
SC
China
MA
E-mail address: [email protected] (Y. Ma)
Keywords: Carbon nitride; Oxygen functional; Near-infrared light; Photocatalysis
D
ABSTRACT: Oxygen functional carbon nitride (NOCN) was synthesized via a moderate
PT E
ultrasonic-assisted method. With highly ordered layered structure and poriferous morphology simultaneously, NOCN was proven to be a new near-infrared light responsive photocatalyst.
CE
Electronic structure was tuned for the intervention of oxygen, which further changed its light
AC
response characters. Different from the previous reported NIR-driven photocatalyst, metal elements were not involved in this material.
1
ACCEPTED MANUSCRIPT 1.
Introduction
As the most promising renewable energy source, solar energy is considered to be one of the major choices in tackling global energy shortage and pollution issues. Extensive research has been conducted in light harvesting materials [1,2]. Considering the solar spectral composition,
PT
photocatalysts that are effective under visible light have attracted more attention in the recent
RI
years [3]. Typically, graphitic carbon nitride (GCN) as a novel “metal-free” semiconductor has
SC
aroused great interest since the pioneering work in 2009 [4]. It has been widespread utilized in versatile redox reactions, bioimaging and material science. GCN is found to show an intrinsic
NU
absorption in the visible region [5-7].Dye sensitization, doping, nanostructure design,
MA
morphological engineering and heterostructure construction are the common strategies to improve the visible light absorption of carbon nitride based materials [8-11]. However, every
PT E
D
step forward in utilizing the solar light is seemingly confined in the short wavelength range.
CE
Near-infrared light, which occupied almost equal proportion of visible light in sunlight, remains underutilized for photocatalysis. Hitherto, two major types of near-infrared light
AC
photocatalysts have been reported, up-conversion photocatalysts and NIR-active photocatalysts. In the former, NIR light is absorbed and converted to UV light by rare earth ions doped fluoride crystals [12] or carbon quantum dots (CQDs) [13] and utilized by TiO2 indirectly. Besides, few NIR-driven photocatalysts, such as Cu2(OH)PO4, Bi2WO6 and Ag/Ag2O heterostructures, etc. have been reported the ability in directly utilizing NIR light recently
2
ACCEPTED MANUSCRIPT [14-16]. Thus, seeking more photocatalysts to achieve the deep exploitation and utilization of solar spectrum in near-infrared part is significative.
Here we demonstrate that oxygen functional layered carbon nitride not only exhibits a much enhanced visible light absorption capability, but also possesses activity under
PT
direct NIR lighting. It is efficient for degradation of Rhodamine B (RhB) in aqueous
RI
solution under NIR light irradiation (λ>800 nm). Nitric acid (HNO 3)-assisted treatment
SC
allows a gentle way to achieve oxygen involved and the fabrication of orderly layered
NU
cancellous structure, which increase significantly the degradation efficiency. Different from the previous reported NIR-driven photocatalyst, metal elements are not involved in
MA
the process. This ensures a more economically feasible and environmentally friendly
Experimental
PT E
2.
D
scheme for near-infrared light hunting.
CE
Bulk carbon nitride (BCN) was obtained from the thermal condensation of urea. Aqueous
AC
HNO3 (2 mol/L) was selected as the oxidant and dispersion medium in ultrasonic process (the aqueous HNO3 treated sample was denoted as NOCN). Photocatalytic degradation of Rhodamine B (RhB) was investigated under near-infrared light (>800 nm) irradiation. The detailed experimental procedures see Supplementary material.
3.
Results and discussion
3
ACCEPTED MANUSCRIPT Elemental analysis (EA) of the NOCN (C/O ratio of 6.9:1) and BCN (C/O ratio of 21.4:1) suggest that oxygen atoms have been introduced during the HNO3 treated process (Table S1). The survey X-ray photoelectron spectroscopy (XPS) spectrum (Fig. 1a) reveals that
PT
the two samples are both mainly composed of C, N and O elements. And more
RI
remarkable, O element increases significantly in NOCN sample, which is consistent
SC
with the results of EA. The chemical bonding between the carbon and nitrogen atoms was futher investigated by high-resolution XPS spectra of C 1s and N 1s spectrum. In C
NU
1s spectrum (Fig. S1a), peaks at 285.1, 288.2 and 289.2 eV are correspond to C-C,
MA
C-N-C coordination, and a trace amount of C-O bonding, respectively [17]. The C1s spectra of the NOCN sample shows enhanced intensity of the peak at 289.2 eV, which
D
derived from C-O bonding also supports the introduction of O atoms, instead of simple
PT E
absorption [18]. Three main binding energies can be separated in the N 1s spectrum 2
(Fig. S1b). Peaks at 398.8, 399.7, 400.7 and 404.4 eV correspond to sp C−N−C 3
CE
bonds, sp H−N−[C]3, C−NHx (amino functional groups) and π excitations [19]. The
AC
weak peak at 404.4 eV almost disappears in the N 1s XPS spectra of NOCN sample. It confirms that the states of delocalized π electrons are affected by the containing oxygen [20], which may influence the surface active sites. The enhancement and peak shift (from 531.8 to 532.2 eV) in the deconvolution of O1s XPS (Fig. S1c) further confirms the oxygen-containing functional groups in NOCN sample [21,22].
4
ACCEPTED MANUSCRIPT As shown in the FT-IR spectrum (Fig. S2), the overall absorbance band intensity of -1
NOCN is stronger than that of BCN. The peaks at 3351, 1705, 1300 and 980 cm , correspond to O-H bonds, C=O bonds, C-O bonds and C-O-C bonds, respectively, which also support the introduction of oxygen atoms [23]. Furthermore, red shift of
RI
PT
absorption peaks of NOCN sample, on account of the change of conjugated structure.
SC
X-ray diffraction (XRD) patterns (Fig. 1b) of the two samples reveal two characteristic peaks located at 2θ=13.0 and 27.4°, corresponding to the in-plane repeating of
NU
tri-s-triazine units and the inter-layer graphite stacking, respectively [24]. Generally,
MA
treated with strong oxidants (such as KMnO 4, concentrated HNO 3 and H2SO4) may induce the damage of the structure order degree [25]. However, after aqueous HNO3
D
treated, the XRD intensity of NOCN significantly enhances, which implying the in-plane
PT E
structure remains untouched. It seems to be a rational explanation to an increased crystallinity of NOCN, especially through the stackig dimension [26]. The interlayer
CE
structure of NOCN sample becomes so much more organized and less
AC
amorphous—than it used to be. Concurrent with the generation of cancellous structure, the long-range ordered interlayer periodic stacking of NOCN has been formed [27]. With the use of the interlayer galleries as diffusion channels, such an orderly layered structure has been proven facilitative for light absorption [28,29].
Without aqueous HNO3 treated in the synthesis process, the morphology of BCN reveals a featureless packed structure (Fig. S3a & b). The overly dense of structural 5
ACCEPTED MANUSCRIPT stacking may block the travel of photon-generated electrons. By contrast, the transmission electron microscopy (TEM) images of NOCN (Fig. S3c & d) display sequential layer structure with numerous in-plane pores, which is analogous to the bone matrix with osteoporosis. These interlaced pores could increase reactive sites and
PT
accelerate the diffusion of photoinduced charge carriers [30]. In this case,
RI
photon-generated electrons could transfer freely throughout the interlamination with
SC
assistance from the enormous pores. The BET surface area of NOCN increases overtly 2 -1
from 48.48 to107.93 m g , 2.2 times as high as that of the BCN. NOCN also possesses
NU
enlarged pore volume (Table S2). This specific structure ensures greater mobility of
MA
photoelectrons.
D
Previous study suggested that GCN is a good visible light active photocatalyst.
PT E
NOCN demonstrates an extended range of light absorption in 300-800 nm (Fig. S4). In addition, the UV/Vis/NIR absorption spectrum of the samples derived from its diffuse
CE
reflectance spectrum (DRS) is shown in Fig. 2. The GCN sample reveals negligible
AC
absorption in the NIR region. Strikingly, the NOCN sample induces an expanded optical absorption beyond 1500 nm, which belongs long-wavelength near-infrared light.
The ability for utilizing of NIR light is confirmed by the photocatalytic degradation for RhB under NIR irradiation (>800nm) (Fig. S5). The degradation rate of RhB for NOCN is over 30% (3h). The circulating water was used to maintain the temperature of RhB solution at 30 °C during extended NIR irradiation. Therefore, the thermocatalytic 6
ACCEPTED MANUSCRIPT reference experiment at 30 °C in the dark was carried out. Thus it can be concluded that the decrement of RhB (about 10%) is resulted from the temperature effect other than BCN sample. Long periods experiment further confirmes that the degradation of RhB resulted from the near-infrared photocatalytic property of NOCN instead of
PT
thermolysis or self-decomposition (Fig. 3a). The renewable catalytic activity of NOCN
RI
photocatalysts was investigated. After four cycles (total duration 96 hours), there is no
SC
obvious decrease in photocatalytic degradation activity (Fig. 3b), suggesting the
NU
superior stable of the NOCN sample.
MA
To study the reaction mechanisms of NOCN photocatalyst, hydroxyl free radical (•OH), hole 2−
+
(h ), and superoxide radical (•O ), as the proposed reactive oxidative species, were evaluated -1
D
using corresponding scavengers. In our experiments, 0.6 mmol L TBA, EDTA and BQ were 2−
+
PT E
used to remove •OH, h , and •O , respectively [31]. The results are shown in Fig. S6. It is +
clear that h , •OH, and •O
2−
+
work in concert to inhibit the photocatalytic activity of NOCN. The 2−
CE
influencing degree is h > •OH > •O .
AC
Albeit the NOCN sample possesses a larger surface area, we speculate that the participation of oxygen is the predominant factor for the conspicuous long-wavelength NIR response. With the accession of oxygen, the electronic structure may be tuned. Thus, we predict four different oxygen-containing structures and calculate the bandgap of GCN unit between HOMO and LUMO (Fig. 4). The results gleaned suggest that structural unit Ⅲ (a downshift by 0.11 eV) and unit Ⅳ (a downshift by 0.26 eV), which with a narrow bandgap are favorably occurred after oxygen inbreak. As known, the heteroatoms with higher periodic 7
ACCEPTED MANUSCRIPT elements could narrow the band gaps of conjugated polymers [32]. Thus, with partial defect of tri-s-triazine aromatic rings, the NOCN in essence reduce the band gap and exploit triumphantly in the near-infrared region. Conclusions
PT
4.
To summarize, oxygen functional layered carbon nitride is proved actived under
RI
near-infrared light in this study. Aqueous HNO 3 assistant-oxygen intervention and the
SC
cancellous structure with high crystalline can significantly improve the
NU
photodegradation efficiency under NIR irradiation. Moderate oxygen intervene has been considered the predominant factor for the conspicuous photoinduced property.
MA
This simple non-metallic material has demonstrated new possibilities of using
PT E
Acknowledgements
D
long-wavelength near-infrared light.
CE
This work was supported by Ministry of Science and Technology of the People’s
AC
Republic of China (2015BAK45B01).
8
ACCEPTED MANUSCRIPT References [1]
A. Fujishima, K. Honda, Nature 238 (1972) 37-38.
[2]
K. Park, Q. F. Zhang, B. B. Garcia, X. Y. Zhou, Y. H. Jeong, G. Z. Cao, Adv. Mater. 22 (2010) 2329-2332. G. Aragay, F. Pino, A. Merkoci, Chem. Rev. 112 (2012) 5317-5338.
[4]
X. C. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J. M. Carlsson, K.
[5]
SC
Domen, M. Antonietti, Nat. Mater. 8 (2009) 76-80.
RI
PT
[3]
Y. Zheng, L. H. Lin, B. Wang, X. C. Wang, Angew. Chem. Int. Ed. 54 (2015) 12868
NU
–12884.
J. S. Zhang, Y. Chen, X. C. Wang, Energy Environ. Sci. 8 (2015) 3092-3108.
[7]
M. K. Bhunia, K. Yamauchi, K. Takanabe, Angew. Chem. Int. Ed. 53 (2014) 11001
MA
[6]
Gu. G. Zhang, S. H. Zang, L. H. Lin, Z. A. Lan, G. S. Li, X. C. Wang, ACS Appl.
PT E
[8]
D
–11005.
Mater. Interfaces 8 (2016) 2287−2296. M. Shalom, S. Inal, C. Fettkenhauer, D. Neher, M. Antonietti, J. Am. Chem. Soc.
CE
[9]
135 (2013) 7118−7121. D. D. Zheng, X. N. Cao, X. C. Wang, Angew. Chem. Int. Ed. 55 (2016) 11512
AC
[10]
–12516. [11]
X. Y. Xia, N. Deng, G. W. Cui, J. F. Xie, X. F. Shi, Y. Q. Zhao, Q. Wang, W. Wang, B. Tang, Chem. Commun. 51 (2015) 10899-10902.
[12]
W. Qin, D. Zhang, D. Zhao, L. Wang, K. Zheng, Chem. Commun. 46 (2010) 2304-2306. 9
ACCEPTED MANUSCRIPT [13]
H. T. Li, R. H. Liu, Y. Liu, H. Huang, H. Yu, H. Ming, S. Y. Lian, S. T. Lee, Z. H. Kang, J. Mater. Chem. 22 (2012) 17470-17475.
[14]
G. Wang, B. B. Huang, X. C. Ma, Z. Y. Wang, X. Y. Qin, X. Y. Zhang, Y. Dai, M. H. Whangbo, Angew. Chem. Int. Ed. 52 (2013) 4810-4813. J. Tian, Y. H. Sang, G. W. Yu, H. D. Jiang, X. N. Mu, H. Liu, Adv. Mater. 25 (2013)
PT
[15]
RI
5075-5080.
H. R. Yang, J. Tian, T. Li, H. Z. Cui, Catal. Commun. 87 (2016) 82–85.
[17]
D. J. Martin, K. P. Qiu, S. A. Shevlin, A. D. Handoko, X. W. Chen, Z. X. Guo, J. W.
SC
[16]
J. Han, L. L. Zhang, S. Lee, J. Oh, K. Lee, J. R. Potts, J. Ji, X. Zhao, R. S. Ruoff, S.
MA
[18]
NU
Tang, Angew. Chem. Int. Ed. 53 (2014) 9240-9245.
Park, ACS Nano 7 (2013) 19-26.
Q. H. Liang, Z. Li, X. L. Yu, Z. H. Huang, F. Y. Kang, Q. H. Yang, Adv. Mater. 27
[20]
PT E
(2015) 4634-4639.
D
[19]
D. H. Deng, K. S. Novoselov, Q. Fu, N. F. Zheng, Z. Q. Tian, X. H. Bao, Nat.
S. N. Guo, Y. Zhu, Y. Y. Yan, Y. L. Min, J. C. Fan, Q. J. Xu, Appl. Catal. B 185
AC
[21]
CE
Nanotechnol. 11 (2016) 218-230.
(2016) 315–321. [22]
H. Wang, S. L. Jiang, S. C. Chen, D. D. Li, X. D. Zhang, W. Shao, X. S. Sun, J. F. Xie, Z. Zhao, Q. Zhang, Y. P. Tian, Y. Xie, Adv. Mater. 28 (2016) 6940–6945.
[23]
T. Yeh, J. Syu, C. Cheng, T. Chang, H. Teng, Adv. Funct. Mater. 20 (2010) 2255 –2262.
10
ACCEPTED MANUSCRIPT [24]
S. B. Yang, Y. J. Gong, J. S. Zhang, L. Zhan, L. L. Ma, Z. Y. Fang, R. Vajtai, X. C. Wang, P. M. Ajayan, Adv. Mater. 25 (2013) 2452-2456.
[25]
J. Oh, R. J. Yoo, S. Y. Kim, Y. J. Lee, D. W. Kim, S. Park, Chem. Eur. J. 21 (2015) 6241-6246. M. J. Bojdys, J. O. Muller, M. Antonietti, A. Thomas, Chem. Eur. J. 14 (2008)
PT
[26]
Y. Y. Kang, Y. Q. Yang, L. C. Yin, X. D. Kang, G. Liu, H. M. Cheng, Adv. Mater. 27
SC
[27]
RI
8177–8182.
(2015) 4572-4577.
A. Mukherji, R. Marschall, A. Tanksale, C. H. Sun, S. C. Smith, G. Q. Lu, L. Z.
NU
[28]
[29]
MA
Wang, Adv. Funct. Mater. 21 (2011) 126-132.
Y. Y. Kang, Y. Q. Yang, L. C. Yin, X. D. Kang, L. Z. Wang, G. Liu, H. M. Cheng,
Z. F. Huang, J. J. Song, L. Pan, Z. M. Ziming, X. Q. Zhang, J. J. Zou, W. B. Mi, X.
PT E
[30]
D
Adv. Mater. 28 (2016) 6471-6477.
W. Zhang, L. Wang, Nano Energy 12 (2015) 646-656. S. F. Chen, Y. F. Hu, S. G. Meng, X. L. Fu, Appl. Catal. B 150–151 (2014) 564–
[32]
AC
573.
CE
[31]
X. G. Ma, Y. H. Lv, Jing Xu, Y. F. Liu, R. Q. Zhang, Y. F. Zhu, J. Phys. Chem. C 116 (2012) 23485-23493.
11
ACCEPTED MANUSCRIPT Figure captions:
Fig. 1 Chemical characterizations of the BCN and NOCN samples. (a) The survey XPS
PT
spectra; (b) XRD patterns.
SC
RI
Fig. 2 The experimental near-infrared absorption spectrum of BCN and NOCN samples.
Fig. 3 (a) Photocatalytic degradation of RhB over NOCN sample from photoctalytic
NU
decomposition (>800 nm), RhB photolysis without catalyst and thermal decomposition (30 °C)
MA
in the dark for long periods (24 h); (b) Cycling runs for the photocatalytic degradation of RhB in
D
the presence of NOCN under NIR light (>800 nm) irradiation.
PT E
Fig. 4 LUMO, HOMO, band gap variation value and schematic illustration of selected structural unit (tri-s-triazine structural unit (A) and structural units (Ⅰ-Ⅳ) with the intervention
AC
CE
of oxygen via a HNO3-assisted treatment).
12
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
Figure 1a
13
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
Figure 1b
14
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
Figure 2
15
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
Figure 3
16
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC
CE
PT E
D
Figure 4
17
ACCEPTED MANUSCRIPT Highlights
Oxygen carbon nitride was synthesized via a simple ultrasonic-assisted method.
Oxygen carbon nitride was proven to be a new near-infrared light responsive photocatalyst. Long-wavelength near-infrared light could be utilized without assist of metals.
The bandgap of oxygen carbon nitride unit between HOMO and LUMO were
PT
AC
CE
PT E
D
MA
NU
SC
RI
calculated.
18