BiOCl nanosheets immobilized on electrospun polyacrylonitrile nanofibers with high photocatalytic activity and reusable property

Applied Surface Science 285P (2013) 509–516

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BiOCl nanosheets immobilized on electrospun polyacrylonitrile nanofibers with high photocatalytic activity and reusable property Yuechen Chou, Changlu Shao ∗ , Xinghua Li ∗ , Chunyan Su, Hongchuan Xu, Mingyi Zhang, Peng Zhang, Xin Zhang, Yichun Liu Center for Advanced Optoelectronic Functional Materials Research, Key Laboratory of UV Light-Emitting Materials and Technology of Ministry of Education, Northeast Normal University, 5268 Renmin Street, Changchun 130024, PR China

a r t i c l e

i n f o

Article history: Received 4 July 2013 Received in revised form 18 August 2013 Accepted 18 August 2013 Available online 28 August 2013 Keywords: BiOCl nanosheets PAN nanofibers Electrospinning Photocatalysis Reuse

a b s t r a c t One-dimensional BiOCl/PAN composite nanofibers which are composed of bismuth oxychloride (BiOCl) nanosheets on electrospun polyacrylonitrile (PAN) nanofibers were fabricated by combining electrospinning technique and solvothermal method. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV–vis diffuse reflectance, Fourier transform infrared spectrum, X-ray photoelectron spectroscopy, thermal gravimetric and differential thermal analysis, were used to characterize the as-fabricated BiOCl/PAN composite nanofibers. The results revealed that BiOCl nanosheets were successfully immobilized on electrospun PAN nanofibers. The contents of the BiOCl nanosheets were controlled by adjusting the precursor concentrations for the fabrication of BiOCl/PAN composite nanofibers during the solvothermal synthesis processes. It was found that some interactions might exist between BiOCl and PAN molecules of BiOCl/PAN composite nanofibers. The obtained BiOCl/PAN composite nanofibers exhibited high photocatalytic activity for degradation of rhodamine B under ultraviolet light irradiation. The trapping experiments confirmed that the main active species for photocatalysis was hydroxyl radicals, which was produced by both the oxidative pathway and reductive pathway. Notably, the BiOCl/PAN composite nanofibers photocatalysts not only had good reusable property because of their one-dimensional structure and flexibility but also retained high photocatalytic stabilities after several cycles due to the interaction between BiOCl and PAN molecules. © 2013 Elsevier B.V. All rights reserved.

1. Introduction Water pollution has been a very serious problem all over the world [1]. The presence of a trace amount of toxic organic compounds, such as dyes and polymer additives, in water bodies and wastewater are harmful to human health and living creatures [2]. In recent years, many methods have been used for treatment of water pollution, such as chemical oxidation, solvent extraction, filtration, adsorption, flotation and photocatalytic degradation [3]. Among the above methods, the photocatalytic degradation of organic compounds in aquatic environment by semiconductor materials has received extensive attention due to its low cost, simplicity and high efficiency as well as no secondary pollution [4–7]. Recently, bismuth oxychloride, BiOCl, is regarded as a promising semiconductor material in decomposing organic compounds for environmental remediation because of their layered structure and indirect optical transition characteristic [8–10]. The layered structure of BiOCl can provide a large enough space to polarize the related atoms

∗ Corresponding authors. Tel.: +86 4315098803. E-mail addresses: [email protected] (C. Shao), [email protected] (X. Li). 0169-4332/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apsusc.2013.08.085

and orbitals, which could induce dipoles that separate the photogenerated electron–hole pairs more efficiently [11]. Besides, BiOCl has an indirect transition band gap of 3.05–3.55 eV [12], so that it is necessary for photo-excited electrons to be emitted to valence band by a certain k-space distance which reduces the recombination probability of photo-excited electrons and holes [13]. The special layer structure and indirect transition characteristic of BiOCl would help to enhance photocatalytic efficiency by promoting the electron–hole separation and charge transport. Some works reported that BiOCl exhibited better performance than TiO2 for photocatalytic degradation of a wide range of organic compounds [14–16]. Therefore, BiOCl could be used as a potential photocatalysts with high efficiency for the treatment of water pollution. In recently years, many kinds of BiOCl and their composite nanostructures have been prepared and investigated because nanostructured photocatalysts could improve photocatalytic efficiency superior to bulks owing to their high quantum yield and high surface areas [17,18]. For example, Jiang et al. have synthesized and studied the faced-dependent photoreactivity of BiOCl single crystalline nanosheets [10]. Mu et al. have grown vertically aligned BiOCl nanosheet arrays on conductive glass substrate which also exhibited high photocatalytic properties [19]. And, in the reports

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by Gao et al., chemically bonded graphene/BiOCl nanocomposites were also prepared and showed significant enhancement in photodegradation of methylbenzene [20]. However, nanostructured BiOCl as photocatalysts present some problems in the separation and recycling process for the suspended nanoparticles, which may increase the cost of industrial applications. In order to solve these problems, many efforts have been devoted to immobilize nanostructured photocatalysts on solid supports [19–28]. Up to now, different dimensional nanostructured materials have been used as supports for photocatalysts, such as nanoparticles and nanofilms [22–26]. However, these nanostructured materials still have some intrinsic drawbacks that are difficult to overcome. For the supports of nanoparticles, the immobilized nanostructured photocatalysts are also easily lost in the process of photocatalytic reaction and separation, which may cause secondary pollution. For the immobilization of nanofilms, it dramatically reduces the interfacial contact between photocatalysts and pollutants, resulting in lower photocatalytic efficiency. We note that electrospun PAN nanofibers have been chosen as a new kind of supports for immobilization of nanostructured photocatalysts [29,30]. With a great potential to overcome these drawbacks, the electrospun PAN nanofibers might be promising supports for immobilization of nanostructured photocatalysts as follows: (a) they possesses the advantages of good electrospinnability and fine stability [31,32], which may make it easy to produce these supports as well as to keep the physical and chemical properties of the composite photocatalysts stable in treating organic wastewater; (b) their high surface area to volume ratio of the one-dimensional nanofibers is beneficial to improve the exposure level of photocatalysts and further enhance the photocatalytic activity; (c) the randomly arrayed nanofibers form macroscopical mats with large continuous surface areas and flexible property, which bring the bulk appearance and characteristics that would be beneficial for the separation, recovery and reuse of the photocatalysts [33,34]. Based on the above considerations, we designed to prepare BiOCl/PAN composite nanofibers with both high photocatalytic activity and reusable property. In our experiment, BiOCl nanosheets were successfully immobilized on the electrospun PAN nanofibers via a simple electrospinning technique and solvothermal method. As expected, the as-fabricated one-dimensional BiOCl/PAN composite nanofibers exhibited excellent photocatalytic activity for the degradation of rhodamine B under UV light irradiation. Moreover, the photocatalysts could be recovered easily and reused without a decrease in photocatalytic activity. 2. Experimental 2.1. Fabrication of PAN nanofibers In a typical procedure, 1.5 g of PAN (Mw ca. 60,000) powders was dissolved in 10 mL of N, N-dimethylformamide (DMF) solution. After vigorous stirring at room temperature for 12 h, a homogeneous solution formed. The above precursor solution was drawn into a hypodermic syringe for electrospinning. The distance between the needle tip and the collector was 12 cm, and the voltage was set at 12 kV. The as-spun PAN nanofiber mats were collected on aluminum foil which was attached on a stainless steel plate. 2.2. Fabrication of BiOCl/PAN composite nanofibers 0.20 mmol Bi(NO3 )3 ·5H2 O and 0.20 mmol KCl were dissolved in 20 mL of ethylene glycol under magnetic stirring for 3 h, followed by the addition of 20 mg PAN nanofibers. Subsequently, the mixture was transferred into a 25 mL Teflon-lined stainless steel autoclave. The autoclave was maintained at 160 ◦ C for 24 h. Then,

the autoclave was cooled down to room temperature naturally. Finally, the obtained BiOCl/PAN composite nanofibers were taken from the autoclave and washed with deionized water and ethanol for several times to remove any ionic residue, and then dried in an oven at 60 ◦ C for 8 h. The as fabricated sample was denoted as S1. By tuning the precursor concentration for synthesizing BiOCl, other samples of BiOCl/PAN composite nanofibers were fabricated and denoted as S2 and S3. Pure BiOCl were fabricated in the absence of PAN with the similar experimental conditions for synthesizing S3. The detailed experimental conditions for the fabrication of all the samples were listed in Table 1. 2.3. Characterization Field emission scanning electron microscopy (FESEM, Quanta 250 FEG Scanning Electron Microscope) was used to characterize the morphology of the products. High-resolution transmission electroscope (HRTEM) images were acquired using a JEOL JEM-2100 (acceleration voltage: 200 kV). X-ray diffraction (XRD) measurement was carried out using a D/MAX-2500 XRD spectrometer (Rigaku) with Cu K␣ line of 0.1541 nm. UV–vis diffuse reflectance (DR) spectroscopy of the samples were recorded on a Lambda 900 UV-vis-NIR spectrophotometer (Perkin-Elmer) and BaSO4 was used as reference. IR spectra were recorded on an Aipha-Centuart FT-IR spectrometer. X-ray photoelectron spectroscopy (XPS) was performed on a VG ESCALAB MK II instrument with Mg K␣-ADES (h = 1253.6 eV) source at a residual gas pressure of below 10−8 Pa. Thermal gravimetric and differential thermal analysis (TG-DTA) was carried out on a NETZSCH STA 449C thermoanalyzer in air atmosphere. The composite nanofibers are heated with temperature increasing rate of 10 ◦ C/min. 2.4. Photocatalytic test The photocatalytic reactor was designed with an internal light source (50 W high pressure mercury lamp with main emission wavelength 313 nm) surrounded by a water-cooling quartz jacket to cool the lamp. 100 mL rhodamine B (RB) solution with an initial concentration of 10 mg L−1 in the presence of solid catalyst (0.02 g) was stirred in the dark for 30 min to reach adsorptiondesorption equilibrium between the organic molecules and the catalysts surfaces. Decreases in the concentrations of dyes were analyzed by measuring the absorbance at  = 553 nm via Lambda 900 UV-vis-NIR spectrophotometer (Perkin-Elmer). At given intervals of illumination, the samples (3 mL) of the reaction solution were taken out for absorption measurements. The effect of scavengers on the performance of photocatalytic degradations of RB was detected by adding 1 mL isopropanol (a quencher of hydroxyl radical), 1 mmol ammonium oxalate (a quencher of holes), or 0.5 mmol Cr(VI) (a quencher of electrons) in the reaction solutions, respectively, the experimental conditions and method of which were the same as the former photocatalytic activity tests. In addition, after the photocatalytic tests, the reusability of the catalyst was also studied only by washing and drying the catalyst for next cycle. 3. Results and discussion The morphologies of the as-fabricated PAN, S1, S2 and S3 were characterized by SEM. Fig. 1a showed that PAN nanofibers had large length to diameter ratios and a relatively smooth surfaces without secondary nanostructures. The diameters of PAN nanofibers ranged from 200 to 300 nm. After solvothermal treatment, the surfaces of nanofibers were no longer smooth. Instead, as shown in Fig. 1(b)–(d), PAN nanofibers were decorated with many BiOCl nanosheets. With increasing precursor concentrations for the fabrication of S1, S2 and S3 during the solvothermal processes,

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Table 1 Experimental conditions, BiOCl nanostructures, and the content of BiOCl in the fabricated samples. Sample

Time (h)

Temperature (◦ C)

S1 S2 S3

24 24 24

160 160 160

a b

Precursor concentrations Bi(NO3 )3 ·5H2 O (mM)

KCl (mM)

10 25 50

10 25 50

BiOCl contenta (wt%)

Morphologyb

29 43 75

Nanosheets Nanosheets Nanosheets

The content of BiOCl was determined by TG. The morphology of BiOCl nanostructures immobilized on the BiOCl/PAN composite nanofibers.

Fig. 1. SEM images of samples: PAN (a), S1 (b), S2 (c) and S3 (d).

the diameters for S1, S2 and S3 were increased correspondingly (∼1.5 ␮m for S3) and the density of BiOCl nanosheets immobilized on PAN nanofibers were also increased significantly. The above results indicated that BiOCl nanostructures were successfully immobilized on the surface of PAN nanofibers and the contents of BiOCl in BiOCl/PAN composite nanofibers were increased with increasing the precursor concentrations. In addition, HRTEM in Fig. 2 revealed the highly crystalline nature of BiOCl nanosheets. The clear lattice fringes with an interplanar lattice spacing of

∼0.275 nm corresponded to the (1 1 0) atomic planes of tetragonal BiOCl [10]. XRD patterns of the as-fabricated BiOCl/PAN composite nanofibers (S1, S2 and S3) were shown in Fig. 3. For the XRD patterns, two peaks marked by solid circles could be attributed to the diffractions of PAN polymers [35], indicating that PAN nanofibers were poorly crystallized. Except the diffraction peaks of PAN, all

Fig. 2. HRTEM image of a single BiOCl nanosheet of S3.

Fig. 3. XRD patterns of samples: S1 (a), S2 (b) and S3 (c).

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Fig. 4. (a) UV–vis diffuse reflectance spectrum of S3. (b) The plot of (␣h)1/2 vs. photon energy (h) for S3.

other diffraction peaks marked by solid squares could be indexed as tetragonal phase BiOCl (JCPDS No. 06-0249). The intense and sharp diffraction peaks indicated that the BiOCl nanosheets had a high degree of crystallization. The intensity of the diffraction peak from the (1 1 0) plane was relatively stronger than that of other planes, which probably related to the growth orientation of BiOCl nanosheets [19]. This result indicated that the nanosheets on S1, S2 and S3 exposed (1 1 0) facets and might exhibited higher activity for direct pollutant degradation under UV light [10]. To investigate the optical property of BiOCl/PAN composite nanofibers, UV–vis diffuse reflectance (DR) spectroscopy of S3 was measured and shown in Fig. 4a. It exhibited the fundamental absorption in the UV region and the absorption edge was located at about 370 nm. As a crystalline semiconductor, the optical absorption near the band edge follows the formula: (˛h)n = B(h − Eg ), where ˛, h, , Eg , and B are the absorption coefficient, Plank constant, light frequency, band gap, and a constant, respectively [36]. Among them, n depends on the characteristic of the transition in a semiconductor, which is either 2 for a direct transition or 1/2 for indirect transition. For BiOCl, the value of n is 1/2 for the indirect transition. Plots of (˛h)1/2 versus photon energy (h) of S3 was shown in Fig. 4b. The estimated band gap energy of S3 was about 3.32 eV, which was a little smaller than the reported values (∼3.50 eV) of bulk crystals [37]. The above results indicated that the BiOCl/PAN composite nanofibers could be used as ultraviolet light active photocatalyst. The FT-IR spectra of sample S3, PAN nanofibers and pure BiOCl were shown in Fig. 5. For the PAN nanofibers, the prominent peaks at about 2242 and 1453 cm−1 were attributed to the stretching vibrations of nitrile groups ( CN) and bending vibration of methylene ( CH2 ) [29,38], respectively. The peak at about 1700 cm−1 might originate from the vibration of C O bonds formed in the

Fig. 5. FT-IR spectra of samples: S3, PAN nanofibers and pure BiOCl.

hydrolyzed PAN nanofibers and the stretching vibration of the C O bonds in residual solvent DMF [39]. For pure BiOCl, the prominent peaks at about 1611 and 522 cm−1 were attributed to flexural vibrations of O H in free water and Bi O stretching mode [40], respectively. For S3, all the characteristic vibration bonds of PAN nanofibers and pure BiOCl were observed. Notably, the peak from Bi O bond vibration was broadened and shifted to large wavenumber, indicating that some interactions might exist between the BiOCl and PAN molecules of the BiOCl/PAN composite nanofibers. However, the peaks originated from PAN in S3 did not show any apparent shift or broaden, probably because the interactions occurred only on the surface of PAN nanofibers. The XPS measurements provided further information for the evaluating the surface chemical compositions. Fig. 6a showed fully scanned spectrum of S3 in the range of 0–800 eV. No peaks of other elements except C, N, O, Cl and Bi were observed in the spectrum. The high-resolution XPS spectra of Bi 4f, Cl 2p and O 1s were shown in Fig. 6(b)–(d). The bands located at binding energies of 163.8 eV and 158.5 eV were assigned to the Bi 4f5/2 and Bi 4f7/2 spin–orbital splitting photoelectrons, respectively. The splitting between these bands was 5.3 eV, indicating the normal state of Bi3+ in BiOCl nanosheets. Furthermore, the binding energies located at 197.1 and 198.6 eV were corresponded to Cl 2p3/2 and Cl 2p1/2 , respectively. In addition, the binding energy at ∼530.8 eV was ascribed to O 1s. The XPS results mentioned above also confirmed the coexistence of BiOCl and PAN molecules in BiOCl/PAN composite nanofibers. Moreover, we also measured the XPS spectra of N 1s for PAN nanofibers and S3 as shown in Fig. S1 in the ESI. The N 1s peak of S3 was much broadened and shifted to higher binding energy compared with pure PAN nanofibers. Considering the IR results, we suggested that the interaction between the BiOCl and PAN might originate from Bi O bonds and the C N bonds interactions. TG and DTA analysis were conducted in order to detect the content of the BiOCl nanosheets immobilized on PAN nanofibers and investigate the interactions between BiOCl and PAN molecules. As observed in Fig. 7a, the weight loss of PAN nanofibers was almost 100% when the temperature reached 670 ◦ C, indicating their complete decomposition. For pure BiOCl, almost no weight loss was recorded from 40 ◦ C to 670 ◦ C, which implied that BiOCl was very stable below 670 ◦ C. For samples of S1, S2 and S3, PAN was completely removed at 670 ◦ C and almost all of BiOCl were left. The weight residues for S1, S2 and S3 at 670 ◦ C were 29%, 43% and 75%, respectively. Therefore, the mass ratios of BiOCl in BiOCl/PAN composite nanofibers from S1 to S2 and S3 were about 29%, 43% and 75%, respectively. The results also confirmed that the contents of BiOCl in BiOCl/PAN composite nanofibers were increased with increasing the precursor concentrations, corresponding to the results of SEM study. For the DTA curves in Fig. 7b, the peak at 318 ◦ C for PAN nanofibers shifted to 327 ◦ C for S3. This peak could be attributed

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Fig. 6. XPS fully scanned spectrum of S3 (a); XPS spectrum of Bi 4f (b), Cl 2p (c) and O 1s (d) for sample S3.

to the cyclization of PAN chains by the elimination of CN [41,42]. It indicated that the presence of BiOCl blocked the elimination of CN and it further supported that the interactions between the BiOCl and PAN might originate from Bi O bonds and the C N bonds interactions. Moreover, the decomposition temperature of S3 also clearly shifted compared to that of PAN nanofibers, which also implied that there might be interactions between BiOCl and PAN molecules. The photocatalytic activity of BiOCl/PAN composite nanofibers was estimated through investigating the degradation of RB solution under UV light irradiation. The characteristic absorption peak of RB at around  = 553 nm was used to monitor the photocatalytic degradation process. The degradation efficiency was defined as C/C0 , where C and C0 stood for the remnant and initial concentrations of RB, respectively. After 30 min of adsorption in dark, the RB

solutions added with different photocatalysts were then subjected to UV light irradiation. The photocatalytic efficiencies of S1, S2 and S3 were illustrated in Fig. 8a. As a comparison, self-decomposition of RB without photocatalysts was also performed under identical conditions. The self-decomposition of RB could almost be neglected. For S1 and S2, the photo-degradation efficiencies of RB were about 49% and 58% after 30 min reactions, respectively. For S3, RB solution was completely photo-degraded within 12 min. The order of photocatalytic activity was S3 > S2 > S1, which was well consistent with that of the content of BiOCl in BiOCl/PAN composite nanofibers. Fig. 8b presented the time-dependent absorption spectra of RB solutions degraded by S3. The main absorption peak diminished gradually and almost disappeared after 12 min. The photographic images inserted in Fig. 8b showed the color of RB solutions which changed from initial red to light

Fig. 7. (a) TG curves of samples: PAN nanofibers, BiOCl/PAN composite nanofibers (S1, S2 and S3), and pure BiOCl; (b) DTA curves of PAN nanofibers and S3 for representation.

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Fig. 8. (a) Self-decomposition of RB (without photocatalyst), and photocatalytic degradation of RB in the presence of BiOCl/PAN composite nanofibers (S1, S2 and S3); (b) absorption spectra of RB solutions with different irradiation time during the photocatalytic process for S3, insets in (b) are photographic images of the corresponding RB solutions at a given time interval.

red and then disappeared with increasing the irradiation time. These results suggested that BiOCl/PAN composite nanofibers had excellent photocatalytic activity for the degradation of RB. The radicals and holes trapping experiments were designed to confirm the pathway of the active species generated in the photocatalytic process. As shown in Fig. 9a, the photodegradation of RB was intensively suppressed after trapping hydroxyl radical (• OH) by adding isopropanol (a quencher of • OH) [43]. It indicated that • OH radical was the main active species during the photodegradation process in our present experiment. It is well known that • OH radical can be formed via two pathways, including the oxidative pathway in which photogenerated holes (h+ ) oxidized water molecules to form • OH, and reductive pathway in which O2 captured the photo-generated electrons (e− ) to produce • O2 − and subsequently produce • OH [44]. To further study the generated pathway of • OH species, ammonium oxalate and Cr(VI) were introduced as the scavengers of active holes and electrons [43], respectively. It could be seen that the addition of ammonium oxalate and Cr(VI) both suppressed the degradation of RB. Therefore, it could be postulated that • OH generated via both the oxidative pathway and reductive pathway in BiOCl/PAN composite nanofibers system under UV light irradiation. Based on the above results, the mechanism of photocatalytic degradation of RB under UV light irradiation for BiOCl/PAN composite nanofibers was proposed and illustrated schematically in Fig. 9b. The probable reactions occurred in this study could be supposed as follows: BiOCl + h(≥E g ) → h+ + e−

(1)

h+ + OH− → • OH

(2)

e− + O2 → • O2 −

(3)

•O − 2

+ H2 O → • HO2 + OH−

(4)

• HO

+ H2 O → H2 O2 + • OH

(5)

2

H2 O2 → 2• OH

(6)

• OH

(7)

+ RB → CO2 + H2 O

Furthermore, the comparative experiments of photocatalytic degradation of RB by PAN nanofibers, BiOCl/PAN composite nanofibers (S3) and pure BiOCl were performed under the same experimental conditions. The mass of pure BiOCl was the same as that of BiOCl in S3. The results were displayed in Fig. 10a. For PAN nanofibers, there was no photocatalytic activity under UV light irradiation, except the adsorption of RB, which could be attributed to the high surface area of the PAN nanofibers. Obviously, the photocatalytic activity of BiOCl/PAN composite nanofibers (S3) was comparable to pure BiOCl. The degradation efficiencies were about 100% and 98% for S3 and pure BiOCl at 12 min, respectively. We noted that BiOCl/PAN composite nanofibers (S3) could be easily separated and recovered from solution because of their onedimensional nanostructure and flexible property. This character assured their well reusable property which was also investigated by collecting and reusing for multiple cycles as shown in Fig. 10b. Each reusability experiment was carried out under the identical condition. It could be clearly observed that the photocatalytic activity

Fig. 9. (a) Effect of scavengers on photocatalytic degradation of RB over S3; (b) proposed mechanism for photocatalysis of BiOCl/PAN composite nanofibers under UV light irradiation.

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Fig. 10. (a) Photocatalytic degradation of RB in the presence of PAN nanofibers, S3 and pure BiOCl; (b) photocatalytic activity of S3 for RB degradation with five times of recycling uses.

of S3 was almost unchanged after 5 cycles of photodegradation of RB. Moreover, the phase and morphology of S3 remained almost unchanged (Figs. S2 and S3 in the ESI), which further confirmed the microstructure stability of S3. The excellent stability of photocatalysts might be attributed to the strong interactions between BiOCl and PAN molecules of BiOCl/PAN composite nanofibers which ensured their low weight lost during the 5 cycles of tests. The good stability and recoverable property would greatly promote the practical applications of BiOCl/PAN composite nanofibers in eliminating organic pollutants from wastewater. 4. Conclusions In summary, we reported a novel strategy to fabricate one-dimensional BiOCl/PAN composite nanofibers by combining electrospinning and solvothermal methods. The contents of BiOCl nanosheets on BiOCl/PAN composite nanofibers could be well controlled by adjusting the precursor concentrations during the solvothermal synthesis processes. The BiOCl/PAN composite nanofibers exhibit excellent photocatalytic activity for the degradation of RB dye under UV light irradiation. More importantly, the BiOCl/PAN composite nanofibers could be easily reused due to their one-dimensional nanostructure and flexible property. The photocatalysts with high photocatalytic activity are very stable for recycling tests. It is expected that the one-dimensional BiOCl/PAN composite nanofibers might be applied as a promising photocatalyst for treatment of wastewater containing organic pollutants. Acknowledgments The present work is supported financially by the National Basic Research Program of China (973 Program) (Grant No. 2012CB933703), the National Natural Science Foundation of China (No. 91233204, 51272041, and 61201107), the 111 Project (No. B13013), the Fund from Jilin Province (Grant No. 20110105), and the Program for Young Scientists Team of Jilin Province (20121802). Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.apsusc.2013. 08.085. References [1] R.P. Schwarzenbach, B.I. Escher, K. Fenner, T.B. Hofstetter, C.A. Johnson, U. Gunten, B. Wehrli, The challenge of micropollutants in aquatic systems, Science 313 (2006) 1072–1077.

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