Ag2CO3 hybrids with highly efficient visible-light-driven photocatalytic activity

Accepted Manuscript In-situ precipitation synthesis of novel BiOCl/Ag2CO3 hybrids with highly efficient visible-light-driven photocatalytic activity Shanshan Fang, Chaoying Ding, Qian Liang, Zhongyu Li, Song Xu, Yanyan Peng, Dayong Lu PII:

S0925-8388(16)31501-8

DOI:

10.1016/j.jallcom.2016.05.168

Reference:

JALCOM 37688

To appear in:

Journal of Alloys and Compounds

Received Date: 6 January 2016 Revised Date:

12 May 2016

Accepted Date: 16 May 2016

Please cite this article as: S. Fang, C. Ding, Q. Liang, Z. Li, S. Xu, Y. Peng, D. Lu, In-situ precipitation synthesis of novel BiOCl/Ag2CO3 hybrids with highly efficient visible-light-driven photocatalytic activity, Journal of Alloys and Compounds (2016), doi: 10.1016/j.jallcom.2016.05.168. 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.

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In-Situ Precipitation Synthesis of Novel BiOCl/Ag2CO3 Hybrids with Highly Efficient Visible-Light-Driven Photocatalytic Activity

Yanyan Pengd, Dayong Lud a

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Shanshan Fanga, Chaoying Dinga,b, Qian Lianga, Zhongyu Lia,c,d*, Song Xua*,

Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology,

b

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China

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School of Petrochemical Engineering, Changzhou University, Changzhou 213164, PR

College of Hua Loogeng, Changzhou University, Changzhou 213164, PR China c

Key Laboratory of Regional Environment and Ecoremediation (Ministry of Education), Shenyang University, Shenyang 110044, PR China Jilin Institute of Chemical Technology, Jilin 132022, PR China

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d

*

Corresponding author. Tel.: +86-519-86334771; Fax: +86-519-86334771

E-mail address: [email protected]; [email protected]

ACCEPTED MANUSCRIPT Abstract Novel BiOCl/Ag2CO3 hybrid photocatalysts were facilely fabricated in situ precipitation method. The as-prepared samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (FE-SEM), X-ray

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diffraction (XRD), Raman spectroscopy, UV-vis diffuse reflectance spectra (DRS), Fourier transform infrared spectra (FT-IR) and photoluminescence (PL). The experiments

indicated

that

the

as-prepared

BiOCl/Ag2CO3

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photocatalytic

photocatalyst exhibited significantly enhanced photocatalytic activity than the pure

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BiOCl and Ag2CO3 samples toward degrading Rhodamine B (RhB) under visible-light irradiation. Moreover, the photocatalytic mechanism of BiOCl/Ag2CO3 hybrid was also discussed. The remarkably improved photocatalytic performance should be ascribed to the heterostructure between Ag2CO3 and BiOCl, which greatly

electrons and holes.

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promoted the photoinduced charge transfer and inhibited the recombination of

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Keywords: BiOCl/Ag2CO3 hybrids; Visible-light photocatalyst; Photocatalytic

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activity; In-situ precipitation method

1. Introduction

Energy conversion and environmental accountability are two major challenges to

the sustainable development of human society. Over the past decades the various advancements in the field of semiconductor-based photocatalysis have received considerable and prime attention, with a focus on solving environment and energy related issues [1-3]. The oldest and traditional semiconductor photocatalysts such as

ACCEPTED MANUSCRIPT TiO2 and ZnO have been extensively studied for such a purpose, they exhibit considerable photocatalytic activity only under UV light (2-4% of the solar spectrum), which greatly limits the practical application for solar energy conversion [2, 4].

to utilize solar energy more efficiently.

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Great efforts have been made to develop visible-light-induced photocatalysts in order

Until now, a variety of visible-light-driven photocatalysts have been reported, such

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as g-C3N4 [5, 6], Bi-based photocatalysts [7-9], Ag-based compounds [10-15],

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plasmonic noble metal (gold, silver) nanoparticles [16], etc. Among which, Ag-based photocatalysts are believed to be promising photocatalysts with high efficiency and have been identified to be well-known photosensitive materials in recent years, including Ag3PO4 [10], Ag3VO4 [11], Ag2O [12], and AgX (X=Cl, Br, I) [13-15].

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More recently, Ag2CO3 semiconductor has been reported for its high-efficient degradation ability for dyes under visible light [17, 18]. Unfortunately, owing to the photocorrosion, the Ag2CO3 semiconductor also exhibits poor stability. To solve this

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problem, Ag2CO3 has been coupled with other semiconductors with matching band

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potential to form a heterojunction at the interface, thus producing Ag2O/Ag2CO3 [19], Ag2CO3/g-C3N4 [20], AgBr/Ag2CO3 [21], AgI/Ag2CO3 [22], Ag2CO3/ZnO [23], Ag2CO3/TiO2 [24], which exhibit better photocatalytic ability and stability than the bare Ag2CO3. These results suggest that heterojunction structure can reduce the recombination of photogenerated charge carriers, and further improve the visibe-light-responsive photocatalytic activity of Ag-based composites. As we all know, BiOCl, is another kind of wide gap bismuth salt, and has the

ACCEPTED MANUSCRIPT internal structure of [Bi2O2]2+ layers interleaved by double slabs of Cl ions, which has been demonstrated to show efficient photocatalytic performance under simulated sunlight irradiation [25, 26]. However, due to its large indirect band gap of about 3.50

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eV, the pure BiOCl has limited photocatalytic activity under sunlight. Moreover, the rapid recombination of photoinduced electrons and holes greatly lowers the quantum efficiency [27]. To further improve the photocatalytic of BiOCl, many studies have

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highlighted the means of controlling the microstructure and morphology [28], or

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doping some elements, compositing it with other semiconductors [27, 29]. Li et al. [30] synthesized BiOCl/Bi24O31Cl10 heterojunction with highly efficient activity through a self-combustion of ionic liquids route. To the best of our knowledge, there is no investigation focused on the BiOCl/Ag2CO3 hybrids for the degradation of dyes.

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In this work, the BiOCl/Ag2CO3 hybrids were synthesized by a facile in situ precipitation method. The as-prepared samples showed relatively high visible-light photocatalytic activities for the photodegradation of RhB in aqueous solution.

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Accordingly, the possible photocatalytic mechanism was proposed.

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2. Experimental

2.1 Synthesis of BiOCl

All the reagents are analytical grade and used without further purifications. Briefly,

5.2088 g Bi(NO3)3•5H2O and 1.4912 g KCl were dissolved in 80 mL ethylene glycol, respectively. Then KCl solution was added into Bi(NO3)3 solution and the mixture was stirred for 1 h and then transferred into 200 mL Teflon-lined stainless steel autoclave and maintained at 160 °C for 12 h. The products were washed once with

ACCEPTED MANUSCRIPT ethanol and three times with distilled water and dried at 60 °C for 5 h. 2.2 Synthesis of Ag2CO3 The Ag2CO3 sample was synthesized by a simple ion exchange method. In a typical

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procedure, 40 mL of silver nitrate aqueous solution (0.1 M) was placed in a beaker and an aqueous solution of solution of sodium bicarbonate (0.05 M) was added dropwise under stirring condition at room temperature. After continuous stirring for

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24 h in the dark, the obtained yellowish green precipitation was collected by

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centrifugation and washed with double distilled water followed by ethanol for several times. Then the product was dried in an oven at 80 °C for 2 h. 2.3 Fabrication of the BiOCl/Ag2CO3 hybrids

The BiOCl/Ag2CO3 hybrids were fabricated by an in situ precipitation strategy. An

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appropriate amount of BiOCl was ultrasonicated in 50 mL of water for 2 h. To this suspension, 0.85 g of silver nitrate was added and stirred for 1 h in the dark. Subsequently, 50 mL of 0.05 M sodium bicarbonate aqueous solution was added

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dropwise and stirred for 24 h in the dark. The obtained precipitation was centrifuged,

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washed with double distilled water followed by ethanol for several times and finally dried at 80 °C for 6 h. A series of BiOCl/Ag2CO3 hybrids were synthesized with different weight ratios of BiOCl and 5, 7.5, 10, 12.5 and 15 wt% BiOCl samples are denoted

as

5%-BiOCl/Ag2CO3,

7.5%-BiOCl/Ag2CO3,

10%-BiOCl/Ag2CO3,

12.5%-BiOCl/Ag2CO3 and 15%-BiOCl/Ag2CO3, respectively. 2.4 Characterization The XRD, TEM, SEM, FT-IR, PL, Raman and UV-vis absorption spectra were used

ACCEPTED MANUSCRIPT to characterize as-prepared samples. The crystalline catalyst was examined by X-ray diffraction (XRD) under a Rigaku D/Max-2500PC X-ray diffractometer (Rigaku Co., Japan) employing Cu Kα radiation, λ = 1.54056 Å operated at 40 kV and 100 mA. A

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JEM-2100 transmission electron microscope (TEM) and a JSM-6360LA scanning electron microscope (SEM, JEOL, Japan) were used to characterize the morphology of the samples. Fourier transform infrared spectra (FT-IR) was recorded in the

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wavenumber range from 400 to 4000cm-1 by Nicolet (PROTéGé 460) spectrometer.

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Raman spectra were measured at room temperature using a LabRAM XploRA Raman spectrometer (Horiba Jobin Yvon, France) with a 532 nm laser focused on a spot about 3 µm in diameter. UV-vis diffuse reflectance spectroscopy (DRS) spectra of the photocatalysts were measured by a UV-vis scanning spectrophotometer (Shimadzu

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UV-2550) using an integrating sphere and BaSO4 as white standard. The photoluminescence (PL) spectra were obtained by an F-280 spectrometer (Tianjin Keqi, China)..

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2.5 Photocatalytic activity

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The photocatalytic activity of the BiOCl/Ag2CO3 samples was evaluated by degradation of Rhodamine B (RhB) solution under visible light irradiation. A 1 kW Xe lamp was used as the light source. In each experiment, 40 mg of the as-prepared photocatalyst was added into 50 ml of RhB solution (15 mg/L). Before irradiation, the suspensions were placed in dark and stirred for 30 min to ensure the establishment of adsorption-desorption equilibrium between the catalyst and RhB. Subsequently, at intervals of every 20 min, about 5 mL of suspension was samples and centrifuged to

ACCEPTED MANUSCRIPT remove the photocatalyst particles. The concentration of filtrates was analyzed by measuring the maximum absorbance at 553 nm for RhB using a UV759 UV-vis spectrometer (Shanghai Precision & Scientific Instrument Co., Ltd., China). The

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decomposition efficiency of the target contaminant was calculated by D = (1 - Ct/C0) × 100%, where C0 and Ct are the equilibrium concentration of the target contaminant before and after visible-light irradiation, respectively.

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3. Results and discussion

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3.1 XRD patterns

XRD studies were carried out to investigate the phase structure and crystalline nature of the synthesized samples. The XRD patterns of BiOCl, Ag2CO3 and the as-prepared BiOCl/Ag2CO3 hybrids with different content of BiOCl are shown in Fig.

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1. The sharp and intense diffraction peaks of the as-prepared samples indicated that all the samples were well crystalline. The characteristic diffraction peaks were detected at 2θ angles of 23.9°, 25.8°, 32.5°, 33.3°, 40.8°, 46.6°, 49.6°, 54.1°, 58.5° and 68.1°

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corresponding to the (002), (101), (110), (102), (112), (200), (113), (211), (212) and

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(220) crystal planes of pure BiOCl could be indexed to the tetragonal phase of BiOCl (JCPDS no. 06-0249), suggesting the high purity. In addition, pure Ag2CO3 displays sharp diffraction peaks (from 15º to 55º) are indexed to (020), (110), (101), (130), (200), (031), (220), (131), (230) and (221) planes of the monoclinic crystal structure (JCPD card no. 26-0339). No other impurities were found, including metallic silver, thus indicating the purity of the as-prepared Ag2CO3. Moreover, following the increase in content of the BiOCl, the intensity of the diffractions of BiOCl displayed

ACCEPTED MANUSCRIPT improvement. It was also found that the intensity of peaks at 2θ = 24.02º and 46.6º are attributed to BiOCl in the BiOCl/Ag2CO3 hybrids. These results could confirm that BiOCl combined with Ag2CO3 closely and that interactions existed between the

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photocatalytic semiconductors. 3.2 FE-SEM images

The FE-SEM morphology and size of samples are observed as shown in Fig. 2. In

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Fig. 2a, the pure BiOCl appear as two-dimensional sheet-like nanostructures with

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uniform thickness of about 40-50 nm and of relatively smooth surface. Fig. 2b shows that the morphology of as-synthesized Ag2CO3 was composed of microcuboids with a length of 0.3-1.0 µm. Fig. 2c revealed that the two types of materials were all found in the sample of 10%-BiOCl/Ag2CO3, and the BiOCl microsphere were assembled on

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the surface of the Ag2CO3 nanocuboids. Obviously, the coexistence of BiOCl and Ag2CO3 does not change their respective morphology. This result further demonstrated the successful synthesis of BiOCl/Ag2CO3 hybrids photocatalyst.

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3.3 TEM images

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Moreover, the crystal structure of the pure BiOCl, Ag2CO3 and the 10%-BiOCl/Ag2CO3 hybrid were further investigated by TEM and the HRTEM (Fig. 3). In Fig. 3a, BiOCl exhibits a hierarchical flower-like structure with a diameter of 1-2 µm composed of nanosheets. Fig. 3b displays that the Ag2CO3 has regular nanoparticle morphology and a relatively smooth surface. From Fig. 3c, it can be seen that BiOCl closely adhered to the surface of the Ag2CO3, resulting in intimate contact, which was beneficial to separate the photogenerated charge carriers. The HRTEM

ACCEPTED MANUSCRIPT image of the 10%-BiOCl/Ag2CO3 photocatalyst is shown in Fig. 3d. The clear lattice stripe indicated that these samples were well crystallized, and the distance of the lattice fringes is 0.273 nm and 0.267 nm respectively, which match well with the

3.4 UV-vis diffuse reflectance spectra

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interplanar spacing of (2 0 0) and (1 0 2) lattice plane of BiOCl.

The light absorption abilities of the as-prepared samples at different light

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wavelengths were investigated by UV-Vis diffuse reflectance spectroscopy, and the

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results were recorded in Fig. 4a. The absorption band edges of pristine BiOCl and Ag2CO3 were estimated to be 375 nm and 470 nm, respectively. It displayed that the as-prepared BiOCl and Ag2CO3 both had strong and broader absorption in the visible light region, suggesting their potential capabilities in the effective utilization visible

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light energy. With the increasing BiOCl content, the BiOCl/Ag2CO3 hybrids exhibited obviously red-shifted compared with Ag2CO3. More interestingly, the absorption intensities of all the BiOCl/Ag2CO3 hybrids showed a significant enhancement in the

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wavelength range of 500-800 nm compared with BiOCl and Ag2CO3. It can be

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attributed to the synergetic effect between BiOCl and Ag2CO3. In the photocatalytic reaction, light-absorbing property of the samples was crucial for the photocatalysis. The band gap of the as-prepared samples was calculated by a related curve of

(Ahv)1/2 versus photon energy (A = absorption coefficient, h = Planck’s constant, m = frequency) plotted, from the intersection of the extrapolated linear portion. The value of BiOCl, Ag2CO3 and BiOCl/Ag2CO3 hybrids (different BiOCl content) was estimated to be 3.41 eV, 2.35eV, 1.72 eV, 1.71 eV, 1.60 eV, 1.65 eV and 1.69 eV,

ACCEPTED MANUSCRIPT respectively (Fig. 4b). This reveals that the band gap of BiOCl/Ag2CO3 hybrids is smaller than that of pure BiOCl and Ag2CO3, and these results also support that all these BiOCl/Ag2CO3 hybrids have suitable band gaps to be activated by visible-light

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for photocatalytic decomposition of organic contaminants. 3.5 FT-IR analysis

In order to attain a better insight for the chemical structures of as-prepared samples,

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FTIR analysis was carried out. As shown in Fig. 6, the broad and strong peak in the

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range of 3200-3550 cm-1 may belong to the stretching vibrations of –OH of adsorbed water molecules, while, the obvious absorption at 1637 cm-1 can be ascribed to deformation vibrations of the –OH groups of adsorbed water molecules [31]. For pure Ag2CO3, the peaks appearing at 1386 and 887 cm-1 are attributed to the characteristic

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absorption bands of CO32- [32]. The representative absorption band of pure BiOCl could be found at 519 cm-1 which was assigned to the Bi-O bond stretching vibration [33-34]. Nevertheless, the FT-IR spectra of BiOCl/Ag2CO3 hybrids are similar to

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those of the main peaks of pure BiOCl and Ag2CO3. Based upon the FT-IR analysis,

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we can deduce that as-synthesized hybrids consist of two components of BiOCl and Ag2CO3 which maintain their original main hybridized structures. 3.6 Raman spectra

Raman spectra of BiOCl, Ag2CO3 and 10%-BiOCl/Ag2CO3 hybrids are shown in

Fig.6. It was found that pure BiOCl showed two distinctive bands and one weak band. The strong band at 144 cm−1 and the band at 197 cm−1 can be assigned to the A1g internal Bi-Cl stretching mode and the Eg internal Bi-Cl stretching mode, respectively.

ACCEPTED MANUSCRIPT The Eg external Bi-Cl stretching was probably overlapped by the strong band at 144 cm−1. The weak band at 396 cm−1 can be ascribed to Eg and B1g band, produced by the movement of the oxygen atoms [35]. The Raman spectra of Ag2CO3 display four

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characteristic peaks located at approximately 710 cm−1, 926 cm−1, 1070 cm−1, 1400cm−1. After the introduction of BiOCl in the BiOCl/Ag2CO3 hybrids, the intensity of the characteristic peaks showed a significant decrease, which may be due

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to the wrapped BiOCl on the surface of Ag2CO3. Not only the typical Raman peaks of

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BiOCl were located at about 143 cm−1, but also the Ag2CO3 typical peaks of at 1070 cm−1, indicating the formation of BiOCl/Ag2CO3 hybrids. 3.7 Photocatalytic activity of BiOCl/Ag2CO3 hybrids

To evaluate the photocatalytic properties of pure BiOCl, Ag2CO3 and

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BiOCl/Ag2CO3, RhB was degraded as a model dye over these photocatalysts under visible-light irradiation at room temperature. Fig. 7a shows the time-dependent absorption spectra of RhB solution in the presence of 10%-BiOCl/Ag2CO3 hybrid

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sample. Under visible-light illumination, the color of RhB solution changed gradually

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from red to colorless during the reaction. The intensity of the absorption peak at 553 nm decreased drastically within 100 min. The degradation efficiency reached 97% after 100 min, which indicated that the 10%-BiOCl/Ag2CO3 sample exhibited high photocatalytic activity.

As shown in Fig. 7b, all BiOCl/Ag2CO3 hybrid photocatalysts exhibit better photodegradation performance than the pure BiOCl and Ag2CO3. Following the increasing BiOCl content, the photocatalytic activity of BiOCl/Ag2CO3 gradually

ACCEPTED MANUSCRIPT improved. BiOCl/Ag2CO3 exhibited the highest photocatalytic degradation efficiency when BiOCl content reached to 10 wt%. However, the photocatalytic activity of BiOCl/Ag2CO3 samples decreased when the BiOCl content was more than 10 wt%. It

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suggested that the optimal content of BiOCl in hybrid photocatalyst was 10 wt%. More BiOCl may reduce the electron transfer efficiency of the photoinduced electrons from Ag2CO3 nanoparticles to BiOCl surfaces, so the activity decreased under

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visible-light irradiation.

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Fig. 7c reveals that the photocatalytic degradation of RhB on different catalysts fits pseudo-first-order kinetics, ln(C0/Ct) =kappt, where t is the irradiation time and kapp is the rate constant. It can be seen that the photodegradation rates of all the BiOCl/Ag2CO3 hybrids are much higher than that of the pure Ag2CO3 and BiOCl

5%-BiOCl/Ag2CO3,

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under visible-light. Concretely, the kapp for RhB degradation with Ag2CO3, BiOCl, 7.5%-BiOCl/Ag2CO3,

10%-BiOCl/Ag2CO3,

12.5%-BiOCl/

Ag2CO3, and 15%-BiOCl/Ag2CO3 were estimated to be 0.0004 min-1, 0.0034 min-1,

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0.0063 min-1, 0.0127 min-1, 0.0314 min-1, 0.0261 min-1 and 0.0111 min-1, respectively.

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These results clearly demonstrated that the BiOCl/Ag2CO3 hybrid photocatalysts system can significantly enhance their photocatalytic activities because of the synergistic effect between BiOCl and Ag2CO3. 3.8 PL analysis

In general, photoluminescence emission spectroscopy (PL) is considered as an effective technology to investigate the migration, transfer and recombination process of photo-generated charge carriers in semiconductors. The higher PL intensity

ACCEPTED MANUSCRIPT represents the lower separation capacity of photoinduced charge carriers and the lower photocatalytic activity in semiconductor-based systems. Fig. 8 shows the PL spectra of the synthesized pure Ag2CO3, BiOCl microsphere and BiOCl/Ag2CO3 hybrids

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recorded at room temperature with an excitation wavelength of 300 nm. The BiOCl/Ag2CO3 hybrid photocatalysts exhibited the emission peaks locating at almost the same position with the pure Ag2CO3. However, emission intensities decreased,

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which suggested that BiOCl/Ag2CO3 hybrids had much lower recombination rate of

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photogenerated charge carriers. The intensity of the 10%-BiOCl/Ag2CO3 hybrid photocatalyst was the lowest among other photocatalysts, indicating that the 10%-BiOCl/Ag2CO3 hybrid had a lowest recombination rate of photo-generated charge carriers. According to the above results, the recombination of photogenerated

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charge carriers was greatly inhibited in the heterostructured BiOCl/Ag2CO3, demonstrating the as-prepared BiOCl/Ag2CO3 hybrids possessed higher separation efficiency than the pure BiOCl and Ag2CO3. Photocatalytic mechanism

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3.9

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In the photodegradation process of organic pollutants, reactive species ·O2¯ , h+ and ·OH acted as a bridge, playing the role of photocatalysts under the light irradiation, therefore, it is necessary to determine the main reactive species for the degradation of RhB in this study. Some sacrificial agents, such as iso-propyl alcohol (IPA), disodium ethylenediaminetetraacetate (EDTA) and 1, 4-benzoquinone (BQ) were used as the scavengers of hydroxyl radical (·OH), hole (h+) and superoxide radical (·O2¯ ), respectively. Fig. 9 shows that the photodegradation efficiency of RhB over

ACCEPTED MANUSCRIPT 10%-BiOCl/Ag2CO3 is not affected by the addition of BQ, indicating that almost no superoxide radicals (·O2¯ ) were involved in the degradation of RhB. When IPA was added, the photodegradation efficiency of RhB obviously decreased, which revealed

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the existence of ·OH radical species. Besides, the photocatalytic activity was thoroughly suppressed by addition of EDTA, suggesting that the h+ pathways play a crucial role in the process of RhB degradation. These results indicated that the h+ and

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·OH were the main active species in the RhB photodegradation process.

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Based on the above analysis, the schematic mechanism of the enhanced photocatalytic activity of the BiOCl/Ag2CO3 hybrids is proposed and shown in Fig. 10. According to previously reported results [36, 37], the EVB values of Ag2CO3 and BiOCl were calculated to be 2.67 and 2.4 eV, and then their homologous ECB values

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were estimated to be 0.37 and -1.1 eV, respectively. Upon exposure to the visible-light, both BiOCl and Ag2CO3 are simultaneously excited to generate electron-hole pairs. The photoexcited electrons on less positive conduction band of BiOCl would prefer to

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flow down to the more positive conduction band of Ag2CO3, while the photogenerated

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holes would flow from more positive valence band of Ag2CO3 to less positive valence band of BiOCl. Besides, Due to the more positive VB level of Ag2CO3 than that of ·OH/OH−, some remained h+ could be transformed into ·OH by oxidizing OH− that absorbed on the surface of the photocatalysts. Thus, the h+ and ·OH were the two active species and play the crucial roles for photodecomposition of RhB. The charge transfer effectively inhibited the recombination of photogenerated electron-hole pairs and thus enhanced the photocatalytic activity.

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BiOCl/Ag2CO3 hybrid were not photocorroded and presented relatively high stability. 4. Conclusions

In summary, the BiOCl/Ag2CO3 visible-light-induced photocatalyst was fabricated

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by facile in situ precipitation method. The photocatalytic experiments demonstrated

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that the BiOCl/Ag2CO3 hybrids exhibit the much better photocatalytic performance than the individual compounds in degradation of RhB under visible-light irradiation. The remarkable photocatalysis enhancement can be attributed to the effective separation of photogenerated electrons–hole pairs, which was due to the

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heterostructure formed between the two semiconductors. Therefore, the facile process using BiOCl/Ag2CO3 heterojunction could be an efficient strategy for the destruction of environmental pollutants.

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Acknowledgments

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This work was financially supported by Open Fund of Key Laboratory of Regional Environment and Eco-remediation of Ministry of Education, China (SYU-KF-E-12), Open Fund of Key Laboratory of Contaminated Environment Control and Regional Ecology Safety, Shenyang University (SYU-KF-L-12), Natural Science Foundation of Jiangsu Province, China (No. BK20150259), Project for Six Major Talent Peaks of Jiangsu Province (2011-XCL-004) and Natural Science Foundation of Changzhou City (CJ20140053).

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ACCEPTED MANUSCRIPT 6951-6953. [26] X.C. Zhang, T.Y. Guo, X.W. Wang, Y.W. Wang, C.M. Fan, H. Zhang, Appl. Catal., B 150-151 (2014) 486-495.

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Li, J. Alloys Compd. 592 (2014) 258-265.

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ACCEPTED MANUSCRIPT [37] N. Tian, H.W. Huang, Y. He, Y.X. Guo, Y.H. Zhang, Colloids Surf., A 467 (2015)

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Figures captions Fig. 1. XRD patterns of pure BiOCl, Ag2CO3 and series of BiOCl/Ag2CO3 hybrids. Fig. 2. FE-SEM images of the pure BiOCl (a), Ag2CO3 (b), as-prepared

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10%-BiOCl/Ag2CO3 hybrids (c). Fig. 3. TEM images of the pure BiOCl (a), Ag2CO3 (b), and higher magnification TEM image of 10%-BiOCl/Ag2CO3 hybrids (c, d).

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Ag2CO3 and series of BiOCl/Ag2CO3 hybrids.

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Fig. 4. UV-vis diffuse reflectance spectra (a), and band gap width (b) of BiOCl,

Fig. 5. FT-IR of pure BiOCl, Ag2CO3 and 10%-BiOCl/Ag2CO3 hybrids. Fig. 6. Raman spectra of as-prepared BiOCl, Ag2CO3 and 10%-BiOCl/Ag2CO3 hybrids.

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Fig. 7. (a) Temporal evolution of the spectra during the photodegradation of RhB over 10%-BiOCl/Ag2CO3 sample; (b) photodegradation of RhB with BiOCl, Ag2CO3 and BiOCl/Ag2CO3 hybrids under visible-light irradiation; (c) kinetic data for the

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degradation of RhB in the presence of different photocatalysts.

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Fig. 8. PL spectra of pure BiOCl, Ag2CO3 and series of BiOCl/Ag2CO3 hybrids. Fig. 9. Effects of different scavengers on the degradation of RhB in the presence of 10%-BiOCl/Ag2CO3 under visible-light irradiation. Fig. 10. Proposed mechanism for the photodegradation of RhB over BiOCl/Ag2CO3 hybrids under visible-light irradiation. Fig. 11. XRD pattern of the 10%-BiOCl/Ag2CO3 before and after the long time experiment.

Ag2CO3

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( -101) ( 020) ( 110)

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Intensity(a.u.)

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( -1 3 0 ) ( 200) ( 031) ( 2 2 0) ( 1 3 1) ( 2 3 0)

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120000

15%-BiOCl/Ag2CO3

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10%-BiOCl/Ag2CO3

•

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5%-BiOCl/Ag2CO3 7.5%-BiOCl/Ag2CO3

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15%-BiOCl/Ag2CO3 BiOCl Ag2CO3

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Highlights

1. Novel BiOCl/Ag2CO3 hybrids were facilely fabricated via in situ precipitation

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method. 2. The BiOCl/Ag2CO3 hybrids showed significant enhancement at visible-light region.

3. The BiOCl/Ag2CO3 hybrids exhibited remarkable visible-light photocatalytic

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activity.

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4. The visible-light photocatalytic mechanism of BiOCl/Ag2CO3 hybrids was

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discussed.