Achieving Enhanced UV and Visible Light Photocatalytic Activity for

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Achieving Enhanced UV and Visible Light Photocatalytic Activity for Ternary Ag/AgBr/BiOIO3: Decomposition for Diverse Industrial Contaminants with Distinct Mechanisms and Complete Mineralization Ability Fang Chen, Hongwei Huang, Chao Zeng, Xin Du, and Yihe Zhang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/acssuschemeng.7b01259 • Publication Date (Web): 24 Jul 2017 Downloaded from http://pubs.acs.org on July 25, 2017

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ACS Sustainable Chemistry & Engineering

Achieving

Enhanced

UV

and

Visible

Light

Photocatalytic Activity for Ternary Ag/AgBr/BiOIO3: Decomposition for Diverse Industrial Contaminants with Distinct Mechanisms and Complete Mineralization Ability Fang Chen,a Hongwei Huang,*,a Chao Zeng,a Xin Du,b Yihe Zhang*,a a

Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid

Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China b

Research Center for Bioengineering and Sensing Technology, Department of Chemistry

& Biological Engineering, University of Science & Technology Beijing, Beijing 100083, China *Corresponding author. e-mail: [email protected] (Hongwei Huang); [email protected] (Yihe Zhang) S

1

ACS Paragon Plus Environment


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ABSTRACT:

Heterojunction fabrication and noble metal deposition serving as

efficacious means for promoting photocatalytic activity attract huge interests. Here, a series of ternary Ag/AgBr/BiOIO3 composite photocatalysts that integrate the above two aspects are prepared by in-situ crystallization of Ag/AgBr on BiOIO3. The photocatalytic performance is first investigated by degrading MO with visible-light and UV light irradiation. The results indicate that Ag/AgBr/BiOIO3 composites present strengthened photocatalytic activity compared with BiOIO3 and Ag/AgBr under both light sources. Distinct activity enhancement levels corresponding to different mechanisms with UV and visible light illumination are uncovered, whch are closely related to the applied light source. The universal catalytic activity of Ag/AgBr/BiOIO3 is surveyed by decomposition of diverse antibiotics and phenols, including tetracycline hydrochloride, chlortetracycline hydrochloride, bisphenol A, phenol, and 2,4-dichlorophenol. which dicloses that this ternary heterojunction photocatalyst demonstrates unselective catalytic activity with universality. Importantly, Ag/AgBr/BiOIO3 displays a strong mineralization ability, completely decomposing BPA into CO2 and H2O. This work affords a new reference for designing heterojunction photocatalyst with multiple advantageous effect and powerful capability for environmental purification. KEYWORDS: photocatalysis; SPR; BiOIO3; AgBr; antibiotics; phenols

2


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INTRODUCTION Photocatalysis with semiconductors, regarded as a green purification tactic, has raised concern due to its prominent abilities for energy generation and environmental purification.1,2 Various types of photocatalysts, like ZnO, TiO2, g-C3N4, and CdS, have been investigated widely. However, these traditional photocatalysts suffer from some drawbacks, like insufficient photoabsorption, photo/photochemical corrosion and high recombination ratio of holes and electrons, which largely confine their applications. Exploration of efficient visible-light-responsive photocatalystic materials is the key to expand and promote the practical applications of semiconductor photocatalyst for environmental purification.3,4 Photocatalytic activity mainly has a correlation with the optical absorption and charge separation and transfer.5 Bismuth-based photocatalytic materials such as bismuth oxyhalides,6,7 bismuth tungstate,8-10 basic bithmuth nitrate or borate,11-13 etc., show great promise for their special layered structure. Among them, BiOIO3, a novel bismuth-based material, possesses superior photocatalytic activity for photodegradation of azo-dyes, NO and Hg removal.14-17 Particularly and very lately, our group discovered the photo and piezoelectric-induced molecular oxygen activation can be realized by BiOIO3.18 The layered crystal configuration of BiOIO3 is composed of (Bi2O2)2+ layers and interbedded (IO3)- anions. The arrangement of polar (IO3)- groups in BiOIO3 results in polarized electric fields and noncentrosymmetrical crystal structure. All of these structural characteristics can greatly facilitate the separation of photoinduced charges, and then 3



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endow BiOIO3 with outstanding photocatalytic activity.19 Nevertheless, BiOIO3 only responds to UV light attributed to its relatively wide band energy (3.0-3.3 eV). To reinforce the light absorption of BiOIO3, many strategies, e.g. doping, metal deposition, surface modification and heterostructure construction, have been achieved.20-23 Among them, developing heterojunction can not only enhance the light response of photocatalyst, but also depress the recombination of photoinduced charge carriers.24,25 For another, silver-species-containing photocatalysts exhibit superior photoabsorption in visible region as a result of Ag surface plasmonic resonance (SPR).26,27 Ag/TiO2 and Ag/AgBr were demonstrated showing high visible-light-responsive photocatalytic activity.28,29 Besides, Ag/AgBr/AgIO3 composites present noteworthy photoactivity for the degradation of MO with irradiation of visible light.30 Consequently, considering the structural benefits of BiOIO3, it is available to simultaneously combine heterojunction and SPR effect to strengthen the photocatalytic performance of BiOIO3. Herein, the Ag/AgBr/BiOIO3 ternary heterojunctions were synthesized by a simple in-situ crystallization approach. The photocatalysis activity of as-obtained photocatalysts are tested via decomposition of methyl orange (MO), phenols and antibiotics separately with visible light and ultraviolet light (UV) illumination. In comparison with the Ag/AgBr and BiOIO3, Ag/AgBr/BiOIO3 photocatalysts show higher photocatalytic properties with a complete mineralization capability. Remarkably, it is found that Ag/AgBr/BiOIO3 shows diverse photocatalytic mechanisms under visble light and UV light illumination, and the photoactivity enhancement level is closely related to the 4


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applied light source. Besides, the ternary Ag/AgBr/BiOIO3 heterojunction photocatalysts are characterized systematically by multiple techniques.

EXPERIMENTAL SECTION Synthesis of the photocatalyst Analytical grade chemicals were used without further disposal. BiOIO3 precursor was prepared via a typical hydrothermal approach. First, I2O5 (0.501 g) and Bi(NO3)3 ▪5H2O (1.455 g) were dissolved in deionized water (25 ml) and 4 ml of concentrated HNO3 with magnetic stirring for 35 minutes. Secondly, a Teflon-lines autoclave (50 ml) containing the above solution was used to complete hydrothermally treatment for 20 h at 180 °C. Then, by filtration and washing alternately with distilled ethanol and water for 3 times, BiOIO3 precursor were finally collected and dried for 6 h at 60 °C. Ag/AgBr/BiOIO3 ternary photocatalysts were fabricated by a simple in-situ precipitation approach. A certain amount of BiOIO3 and AgNO3 were added in deionized water (25 ml). Next, 25 ml of KBr with KBr/BiOIO3 molar ratios of 10%, 20%, 40%, 80%, 150% and 300% were dissolved in the above suspensions dropwise. They were stirred at ambient condition for 1 h, and then the composites were filtrated and dried completely. According to the different KBr/BiOIO3 molar ratios, the composites were denoted

as

10%Ag/AgBr/BiOIO3,

20%Ag/AgBr/BiOIO3,

40%Ag/AgBr/BiOIO3,

80%Ag/AgBr/BiOIO3, 150%Ag/AgBr/BiOIO3 and 300%Ag/AgBr/BiOIO3, respectively.

5



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The emergence of metallic Ag is resulted from AgBr by the surrounding-light reduction. The formation schematic diagram was shown in Scheme.1 Characterization X-ray powder diffraction (XRD, Bruker D8, Germany) is applied to confirm the phase structure of BiOIO3 series products. The scanning electron microscopy (SEM, Hitachi, Japan) was employed to analyze the morphology. Meanwhile, the transmission electron microscopy (TEM) and high-resolution TEM (HRTEM, JEOL, Japan) were also used to analyze the microstructure. UV-vis diffuse reflectance spectra (DRS, Varian Cary 500, USA) was implemented to survey the optical properties. The surface composition for a series of as-synthesized photocatalysts were studied by the X-ray photoelectron spectroscopy. The photoluminescence (PL) spectra (Hitachi, Japan) are employed to further investigate the charge recombination rate. Photocatalytic experiment The degradation of diverse contaminants and antibiotics, including methyl orange (MO,

2*10-5

mol/L),

tetracycline

hydrochloride

(10

mg/L),

chlortetracycline

hydrochloride (10 mg/L), bisphenol A (BPA, 10 mg/L), phenol (10 mg/L) and 2,4-dichlorophenol (2,4-DCP, 10 mg/L) were conducted to inspect the photocatalytic properties of Ag/AgBr/BiOIO3 with visible light (500 W Xe lamp with 420 nm cut-off filters) or UV light (300 W mercury lamp) irradiation. 25 mg of photocatalysts were ultrasonically dispersed in contaminant aqueous solution (50 ml). After stirring for 30 min in darkness, the adsorption-desorption balance was got. In the experiment of 6


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degradation, about 3 ml of suspension was extracted at each 1 minute or half an hour. Then, the supernatant was obtained by centrifugation and investigated by recording the absorption spectra of pollutants. Active species trapping test For revealing the active species produced in the degradation reaction, the trapping agents, including isopropanol, ethylene diaminetetraacetic acid disodium and p-benzoquinone were used for trapping hydroxyl radicals, holes and superoxide radicals, respectively.31 During the photocatalytic process of MO, the different trapping agents (the amount of quenching agents was 1mmol) were dissolved in the MO solution. The next procedures are the same as the aforementional MO photodegradation processes. Photoelectrochemical measurements The electrochemical impedance spectra and photocurrent response measurements were conducted on an electrochemical system (CHI-660E, Chenhua Instruments Co, China) with the 0.1 mol/L Na2SO4 solution as electrolyte. The as-prepared sample films on ITO glass and saturated calomel electrode are working electrode and reference electrode, respectively. Platinum wire was used as the counter electrode. The measurement was performed under simulated solar light irradiation (300 W xenon bulb). The applied voltage is 0.0 V in this measurement of transient photocurrent, To prepare the working electrodes of Ag/AgBr, BiOIO3 and Ag/AgBr/BiOIO3, 15 mg of the samples were completely dispersed in 1ml of ethanol. Subsequently, the obtained slurry was drop-coated on a 20mm*40mm ITO glass, and exposed to air for 24 h to be dried. 7



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RESULTS AND DISCUSSION Structure, microstructure and composition To study the crystallographic structure of samples, XRD patterns of a series of Ag/AgBr/BiOIO3 ternary composites, BiOIO3, and Ag/AgBr and are shown in Fig. 1. The diffraction peaks of Ag/AgBr and BiOIO3 coincide with the standard data of Ag (JCPDS #1-1164), AgBr (JCPDS #1-950) and BiOIO3 (ICSD #262019), respectively. With respect to the Ag/AgBr/BiOIO3 composites, their XRD patterns apparently change with increasing the molar ratio of KBr to BiOIO3. The peaks at 27.6°, 30.9° and 37.9° correspond to the characteristic peaks of BiOIO3, AgBr and Ag, which are highlighted by red, purple and blue stripes, respectively. With the increase of the ratio of KBr to BiOIO3, the intensity of peaks for BiOIO3 gradually decrease, and on the contrary the peaks intensity for AgBr and Ag continuously increases. The peaks of Ag are not obvious for 10%, 20% and 40%Ag/AgBr/BiOIO3 samples, which is probably attributed to the high dispersity and low content of Ag. The above results demonstrate that the ternary Ag/AgBr/BiOIO3 composites are obtained by this in-situ deposition reaction, and the crystalline phase of BiOIO3 is not severely effected with the introduction of Ag/AgBr. The chemical state and surface element compositions of 150%Ag/AgBr/BiOIO3 are inspected via X-ray photoelectron spectroscopy. As depicted in Fig. 2a, it consists of Ag, Br, O, Bi, I and C elements. The Bi 4f XPS spectra are showed in Fig. 2b. The two peaks centering at 164.4.0 eV and 159.0 eV can be separately attributed to the Bi 4f5/2 and Bi 8


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4f7/2 of Bi3+ ions. The O 1s high-resolution XPS spectrum is presented in Fig. 2c. The peaks located at 530.34 eV and 531.21 eV are attributed to the Bi-O bonds and the hydroxyl groups (-OH) absorbed on the surface, respectively.23 As exhibited in the Ag 3d spectrum (Fig. 2d), it consists of two sets of peaks. The binding energies of 367.8 eV, 368.6 eV, 373.7 eV and 374.6 eV match with Ag+ 3d5/2, Ag 3d5/2 , Ag+ 3d3/2, and Ag 3d3/2 of Ag0, respectively. The XPS results verify that the as-prepared 150%Ag/AgBr/BiOIO3 contains Ag+ and Ag0, 2,32,33 Both the XPS and XRD results are consistent. The existence of metallic Ag is attributed to the photoreduction by the surrounding light in the preparation process. The microstructure, morphology and element distribution of as-synthesized samples are analyzed by TEM, HRTEM, SEM and EDX-mapping. As depicted in Fig. 3a, the pristine BiOIO3 displays a flake structure with smooth surface and width of 0.2-2 µm and thickness of ~10 nm. Fig. 3b shows the SEM image for Ag/AgBr. The size of AgBr particles is 1-2µm, and the nanoparticles observed on the surface of AgBr are Ag. As depicted in the SEM images of Ag/AgBr/BiOIO3 composites (Fig. 3c-d), one can obviously observe that the products are composed of Ag/AgBr paticles and BiOIO3 flakes, and the morphology of BiOIO3 does not show obvious changes. Fig. 3e depicts the schematic illustration on the formation of Ag/AgBr/BiOIO3 heterojunction, which can give a direct and clear picture on the synthetic process. The TEM image of BiOIO3 are exhibited in Fig. 4a, which confirms the flake structure of BiOIO3. As presented in Fig. 4b, the HRTEM pattern of BiOIO3 displays the lattice fringe with a distance of 0.33 nm, in 9



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line with the (121) plane of BiOIO3. TEM images of 150%Ag/AgBr/BiOIO3 of before and after irradiation under the transmission electron beam within extremely short time are presented in Fig. 4c-d. The particles in the highlighted area show obvious contraction after electron beam irradiation, which can be ascribed to the decomposition from AgBr to Ag with eletron beam irradiation. It also accounts for appearance of Ag in the Ag/AgBr/BiOIO3 composites.33 Fig. 4e-h displays the EDX-mapping of the 150%Ag/AgBr/BiOIO3 sample. It can be observed that Ag, Br, Bi and O uniformly distributed across the Ag/AgBr/BiOIO3. The EDX of 150% Ag/AgBr/BiOIO3 sample was performed to identify the phases of Ag, AgBr and BiOIO3 in the Ag/AgBr/BiOIO3. As exhibited in Fig. 5, the signal of Au is resulted from instrument. The EDX result provides solid evidence that the three phases of Ag, AgBr and BiOIO3 co-exist in the composite photocatalyst. The speciﬁc surface area of photocatalysts is surveyed by BET adsorption-desorption method. It can be found that the surface area of 150%Ag/AgBr/BiOIO3 (5.7 m2/g) shows no big difference with that of pure BiOIO3 (6.2 m2/g) and Ag/AgBr (1.2 m2/g), which would not contribute to the photocatalytic performance enhancement of composites. Photoabsorption properties and band gap To

inspect

the

optical

absorption

properties

of

Ag/AgBr,

BiOIO3

and

Ag/AgBr/BiOIO3 composites, they are examined by UV-vis diffuse reflection spectroscopy. The absorption edge of primary BiOIO3 locats at approximately 400 nm As 10


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exhibited (Fig. 6a), and its bandgap is 3.1 eV, implying that pristine BiOIO3 can hardly absorb visible light. On the contrary, the Ag/AgBr sample shows effective photoabsorption in visible range, and its absorption edge is about 500 nm. As the Ag/AgBr content increases, the absorption edges of Ag/AgBr/BiOIO3 composites gradually red-shift to visible light region. Meantime, an absorption peak centering around 550 nm in visible light range is observed, corrsponding to the Ag surface plasmon resonance absorption.30 Band gap energies for BiOIO3 and Ag/AgBr can be determined based on the following Kubelka-Munk (KM) equation: αhγ=A(hγ-Eg)n/2

(1)

here γ, h, α are the photon frequency, Planck’s constant and optical absorption coefficient, respectively. Eg and A represent the band gap energy and a constant, respectively. The n value relys on the semiconductor type. The electronic transition for BiOIO3 and Ag/AgBr is indirect-allowed, so the n is 4. The band gaps of the pure BiOIO3 and Ag/AgBr are 3.00 and 2.30 eV, respectively (Fig. 6b). Photodegradation of MO under UV light irradiation The photocatalytic properties of BiOIO3, Ag/AgBr and Ag/AgBr/BiOIO3 composites are assessed by choosing MO as a representative pollutant for degradation.34,35 Because pure BiOIO3 principally responds to UV light, MO degradation experiments of pure BiOIO3, Ag/AgBr and the composite samples were first conducted under UV light 11



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irradiation, and their photocatalytic degradation curves are displayed in Fig. 7a. It is clear that the photocatalytic activities of all the as-obtained composite photocatalysts are better than that of BiOIO3. But, only 150%Ag/AgBr/BiOIO3 that removes 87.7% of MO after 4 min UV light irradiation outperforms Ag/AgBr. As displayed in Fig. 7b, the photodegradation rate constant for BiOIO3, Ag/AgBr and 150%Ag/AgBr/BiOIO3 is 0.128 min-1, 0.642 min-1 and 0.697 min-1, respectively. Namely, the photoactivity of 150%Ag/AgBr/BiOIO3 is separately 5.4 and 1.1 times higher than that of BiOIO3 and Ag/AgBr. The temporal absorption spectra of MO for BiOIO3, 150%Ag/AgBr/BiOIO3 and Ag/AgBr are exhibited in Fig. 7c-d and Fig. S1. It confirms that MO is gradually destroyed by these catalysts. Photodegradation of MO and 2,4-DCP with visible-light illumination Fig. 8a displays photodegradation curves of MO with visible light (λ > 420 nm) illumination. BiOIO3 shows a negelectable degradation efficiency due to its poor visible-light absorption. Distinct from UV-light degradation, all the composite photocatalysts exhibit remarkably enhanced degradation capability than pristine samples with

visible

light

illumination.

150%Ag/AgBr/BiOIO3

still

shows

the

best

photo-reactivity among the photocatalysts, where the degradation efficiency reach approximately 92% within 0.5 h, far exceeding that of BiOIO3 (1.3%) and Ag/AgBr (18%). To make quantitative comparison, the photodegradation rate of these samples was determined via the following formula: 23 ln(C/C0) = -kappt

(2)

Here t is time of the reaction. C and C0 represent the MO concentration at t and the initial 12


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MO concentration, respectively. kapp represents the apparent rate constant. As displayed in Fig. 8b, the apparent rate of BiOIO3, Ag/AgBr and 20%, 40%, 80%, 150%, 300%Ag/AgBr/BiOIO3 are calculated to be 0.015, 0.361, 0.903, 0.554, 1.856, 2.736 and 2.604 h−1, respectively. The 150%Ag/AgBr/BiOIO3 shows the highest photocatalytic efficiency, which is about 180 and 7.5 times that of the pure BiOIO3 and Ag/AgBr, respectively. The instantaneous absorption spectra of MO over BiOIO3, Ag/AgBr and 150%Ag/AgBr/BiOIO3 are provided in Fig. 8c-e. The concentration of MO solution gradually declines

with

increasing the illumination time,

demonstrating the

decomposition of MO molecules. For further confirming the consumedly reinforced photocatalytic activitiy of as-obtained photocatalysts, degradation experiment toward 2,4-dichlorophenol (2,4-DCP) was carried out. It can be found from Fig. 8f that the 150%Ag/AgBr/BiOIO3 possesses the highest photocatalytic performance among the three catalysts. Fig. 8g, h and Fig. 9a show the absorption spectra over BiOIO3, Ag/AgBr and 150%Ag/AgBr/BiOIO3. The characteristic absorption band of 2,4-DCP gradually decreases with increasing the irradiation time, and the 2,4-DCP concentration catalyzed by 150%Ag/AgBr/BiOIO3 shows the fastest decline, confirming the best photocatalytic performance. Compared to the UV-light degradation, the composite catalysts present evidently higher activity enhancement with irradiation of visible-light degradation, which means the different photocatalytic mechanisms under different light sources (UV and visible light). Photodegradation of diverse industrial pollutants and antibiotics 13



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To eliminate the dye sensitization effect and further confirm the universally photocatalytic capability of 150%Ag/AgBr/BiOIO3 composite photocatalyst, diverse stubborn

contaminants,

including

tetracycline

hydrochloride,

chlortetracycline

hydrochloride, colorless phenol and bisphenol A (BPA), are selected as the target with the visible light (λ > 420 nm) illumination. Fig. 9a-e show the temporal absorption spectra of chlortetracycline hydrochloride, tetracycline hydrochloride, BPA, phenol and 2,4-DCP over 150%Ag/AgBr/BiOIO3. 150%Ag/AgBr/BiOIO3 can efficiently decompose these pollutants and antibiotics. After 5h illumination, the removal efficiencies are 47.8%, 40.0%, 20.0%, 34.2% and 31.4% for chlortetracycline hydrochloride, tetracycline hydrochloride, BPA, phenol and 2,4-DCP, respectively (Fig. 9f), confirming the nonselective photocatalytic activity.

Mineralization ability of Ag/AgBr/BiOIO3 composite photocatalyst To investigate the mineralization ability of 150%Ag/AgBr/BiOIO3 composite photocatalyst, the total organic carbon (TOC) of BPA as a typical stubborn contaminant was analyzed. Fig. 10 displays the TOC data and the degradation efficiency of BPA solution over 150%Ag/AgBr/BiOIO3 composite for 0, 2 and 4 h irradiation. As revealed, both the photodegradation efficiency and mineralization ratio of organic carbon of BPA after 4 h visible-light irradiation is 70.9% and 71.0%, respectively. It indicates that all the degraded BPA is decomposed into CO2 and H2O, manifesting the complete mineralization ability of Ag/AgBr/BiOIO3 composite photocatalyst. Stability of Ag/AgBr/BiOIO3 composite photocatalyst 14


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The cycling experiment is implemented to study the stability and recyclability of the modified 150%Ag/AgBr/BiOIO3 catalyst for MO degradation. As exhibited in Fig. 11a and b, the original MO degradation efficiency is 95.4% within 1.5 h. After three times of cycles, the MO degradation ratio is still 93.5%, implying that the excellent photocatalytic activity of the 150%Ag/AgBr/BiOIO3 is well kept. To further verify the stability of as-obtained samples, the XPS and XRD after photoreaction were conducted. The XRD has no obvious change (Fig. 11c), compared with that of 150%Ag/AgBr/BiOIO3 before photocatalytic test. The Ag XPS spectrum of the 150%Ag/AgBr/BiOIO3 after photoreaction is displayed in Fig. 11d. Through the comparison of the XPS spectra before and after photoreaction, it can be found that the peak intensity corresponding to metallic Ag did not increase, demonstrating that no obvious decomposition for AgBr into metallic Ag occurred during the photodegradation process. It is likely ascribed to the efficient separation of holes and electrons in Ag/AgBr/BiOIO3, which then rapidly participate in the reaction. These evidences apparently demonstrate that the 150%Ag/AgBr/BiOIO3 composite photocatalyst has a high stability against to photo/photochemical corrosion. Charge separation, reactive intermediate and photocatalytic activity enhancement mechanism Photocurrent is valid technique to reveal the charge separation and transfer dynamics that take an crucial role in the photodegradation process.35 Fig. 12a shows the transient photocurrent responses of pure BiOIO3, Ag/AgBr and 150%Ag/AgBr/BiOIO3 with 15



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visible light illumination. Compared with pristine BiOIO3 and Ag/AgBr samples, the photocurrent

intensity

for

150%Ag/AgBr/BiOIO3

is

markedly

strengthened,

demonstrating the promoted charge separation. The electrochemical impedance spectra (EIS) were implemented to reflect the interfacial transfer efficiency of photo-induced electrons and holes. The Nyquist plots of BiOIO3, Ag/AgBr and 150%Ag/AgBr/BiOIO3 with light irradiation are shown in Fig. 12b. Generally, a small radius represents a high electrons and holes transfer efficiency. Compared with pure BiOIO3 and Ag/AgBr, it can be found that the 150%Ag/AgBr/BiOIO3 composite shows a relatively smaller radius, revealing that the interfacial charge transfer efficiency has been obviously increased. As displayed in the inset of Fig. 12b, the EIS data were fitted by an equivalent circuit to obtain a quantitative understanding. Here, Q, R, RCT, Cdl, RΩ represent the constant-phase element, the reaction resistance, the charge transfer resistance, the electric double layer capacitor and the ohmic resistance, respectively. Generally, the arc diameter is positively correlated with the RCT. In this work, RCT is approximated 2407, 2368 and 913 Ω for pristine BiOIO3, Ag/AgBr and 150%Ag/AgBr/BiOIO3 samples, respectively, suggesting that the 150%Ag/AgBr/BiOIO3 composite possesses the smallest charge transfer resistance. The above result further affirms that formation of Ag/AgBr/BiOIO3 heterojunction benefits

charge transfer.36 Photoluminescence spectroscopy (PL) was

employed to further investigate the charge separation rate. Generally, the low photocatalytic capability corresponds to the high fluorescence intensity, which is caused by high bulk recombination.37 As revealed by Fig. 12c, the series of emission peaks of 16


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BiOIO3, Ag/AgBr and 20%, 80%, 150%, 300%Ag/AgBr/BiOIO3 samples locate at approximately 390 nm with excitation of 245 nm light. The 150%Ag/AgBr/BiOIO3 sample displays the weakest emission intensity, implying the most excellent separation of photoinduced holes and electrons. The above results may give a good explanation for why the 300%Ag/AgBr/BiOIO3 sample shows the highest photoabsorption in all the photocatalysts, but its performance is not the best. Compared with light absorption, charge separation efficiency probably takes a dominant role in reinforcing photocatalytic performance.38 To inspect the band structure, Mott-Schottky method was employed for calculating the flat band (Efb) potentials:39 1

C2

=

2  κT  E − E fb − B q εε 0 N D 

(3)

  

herein q, T, κb, Efb and E are the electronic charge, the temperature, Boltzmann’s constant, the flat-band potential and applied potential, respectively. ND is donor density. C is the charge capacitance. ε0 and ε indicates the film and the dielectric constants. As exhibited in Fig. S2, BiOIO3 is a n-type semiconductor because of the positive slope. To calculate the x-intercept, the flat band potentials (Ffb) of BiOIO3 is determined to be -0.62 eV relative to saturated calomel electrode (SCE), amounting to -0.38 eV vs. the normal hydrogen electrode (NHE). Becasue the flat potential is 0.1-0.3 eV lower than the conduction band position,16 the conduction band (CB) level of BiOIO3 is calculated as -0.68 eV, and the valence band (VB) position of BiOIO3 is estimated to be 2.32 eV.

17



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The trapping experiments were implemented to explore the main active species in the photodegradation reaction. P-benzoquinone (BQ), isopropanol (IPA) and Ethylene diaminetetraacetic acid disodium (EDTA-2Na) are utilized to capture superoxide radicals (•O2−), hydroxyl radicals (•OH) and holes (h+) in the experiments of MO photodegradation, respectively.17 For the 150%Ag/AgBr/BiOIO3 composite, as presented in Fig. 13a-d, with the addition of BQ, the photodegradation of MO is seriously inhibited under the UV light illumination. It can be concluded that the •O2− playes a greater part in the photodegradation test. Compared with the trapping experiments with illumination of visible-light for Ag/AgBr sample, under the UV light irradiation, the degradation of MO is remarkably reduced by adding p-benzoquinone (BQ), and slightly inhibited by adding ethylene diaminetetraacetic acid disodium (EDTA-2Na). It appears that •O2− is the primary active species and h+ plays as a subordinate role. As shown in Fig. 13e-f, for pure BiOIO3 sample with illumination of UV light, h+ and •O2− dominate the degradation process. Under visible light irradiation, h+, •O2− and •OH all have influence on the photocatalytic process (Fig. 14a-b), implying that •OH, •O2− and h+ are active species for the photocatalytic degradation. For Ag/AgBr sample, as the shown in Fig. 14c-d, hydroxyl radicals (•OH) have few influence on the photodegradation. By contrast, the degradation rates of MO are significantly reduced when h+ and •O2− have been trapped, revealing that •O2− and h+ are the primary active species. As seen from Fig. 14e-f, BiOIO3 cannot be activated by visible-light, resulting in almost no active species. Based on the experimental results above, the photocatalytic mechanisms for 18


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Ag/AgBr/BiOIO3 under both light sources are separately proposed, as depicted in Fig. 15. It is reported from the previous study that the CB of BiOIO3 comprises I 5p, O 2p and Bi 6p orbitals, and the VB mainly consists of O 2p orbitals.23 As exhibited in Fig. 15a, under the excitation of UV-light, both BiOIO3 and AgBr can produce electron-hole pairs. The CB of AgBr is -0.30 eV. The CB of BiOIO3 is -0.68 eV, which is more negative than that of AgBr, thus the electrons of BiOIO3 would migrate onto the CB of AgBr, and then transfer to Ag. The more positive potential of BiOIO3 favors the transfer of the holes from BiOIO3 to the VB of AgBr. The electrons would reduce O2 to •O2−. Because the VB of AgBr (2.00 eV) is very close to or lower than the redox potentials of •OH/H2O (2.27 eV) and OH−/•OH (1.99 eV), the oxidation ability of holes is insufficient to oxidize OHto •OH. As only •O2− functions as active species, Ag/AgBr/BiOIO3 composite thereby displays

moderately

improved

photocatalytic

performance

with

UV

light

illumination.40-41 Fig. 15b exhibits the speculated photocatalytic mechanism for Ag/AgBr/BiOIO3 with illumination of visible light. BiOIO3 barely absorbs visible light on account of its wide band gap (3.0 eV) and it almost does not produce holes and electrons. Ag/AgBr/BiOIO3 display drastically reinforced photocatalytic performance in contrast to the pure samples under visible light. Synergistic effect of Ag nanoparticles SPR effect and fabrication of heterojunction are the main reasons. Because of the SPR effect of the metallic Ag, it can respond to visible light (550 nm) to produce holes and electrons. The photoinduced electrons on the Fermi level (0.4 eV) of Ag could be motivated to excited states, and 19



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transfer to the CB of BiOIO3 and AgBr, leaving positive charges. In order to recover the primal state, Ag needs to accept electrons from the VB of BiOIO3. The above factors can increase charge carriers lifetimes and depress the recombination of holes and electrons.40 In addition, the near-field resonant energy transfer of Ag could accelerate the production and separation of hole-electron pairs in BiOIO3. The VB of BiOIO3 is 2.32 eV, which is more positive than that of •OH/H2O (2.27 eV) and OH−/•OH (1.99 eV),39 hence OH− can be oxidized to •OH by holes. At the same time, the electrons and holes can be activated on AgBr with a relative narrow band gap (2.30 eV). The ECB and EVB of AgBr are separately -0.30 and 2.00 eV. The maximum energy (2.95 eV) of the visible light can effectively excite the AgBr semiconductor, and the photogenerated electrons in VB of AgBr can jump into a higher band energy level.40-44 Together with the electrons transferred from Ag, it results in that more electrons react with O2 and large amount of superoxide radicals (•O2−) are produced, and O2 is reduced to •O2− under the action of the electrons from the CB of BiOIO3 . Therefore, benefiting from the synergistic effect of metallic Ag SPR effect and charge transfer in heterojunction, •O2−, •OH and h+ all can be produced as active species. As a results, consumedly enhanced photocatalytic performance is achieved in Ag/AgBr/BiOIO3 heterojunction with visible light irradiation.42-44

CONCLUSIONS 20


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In conclusion, ternary Ag/AgBr/BiOIO3 heterojunction photocatalytic materials were successfully fabricated by a readily-achievable in-situ precipitation approach. Compare with the pristine BiOIO3, the Ag/AgBr/BiOIO3 composite photocatalyst exhibits moderately (5.4 and 1.1 times superior than BiOIO3 and Ag/AgBr) and significantly (180 and 7.5 times superior than BiOIO3 and Ag/AgBr) strengthened photocatalytic activity with UV and visible light illumination, respectively, which correspond to different photocatalytic mechanisms. With illumination of UV light, charge transfer happens between bands and •O2− serves as the only active specie. In contrast, •O2−, •OH and h+ are all produced and play important roles with illumination of visible light because of charge transfer and the SPR effect of metallic Ag, contributing to the consumedly enhanced photocatalytic performance. Moreover, Ag/AgBr/BiOIO3 shows high photo-oxidation performance for decomposing MO, tetracycline hydrochloride, chlortetracycline hydrochloride, bisphenol A (BPA), phenol and 2,4-dichlorophenol (2,4-DCP). under visible light illumination, and its strong mineralization ability is unearthed. This study pave new way for development of high-performance ternary composite photocatalytic materials for environmental applications.

■ASSOCIATED CONTENT Supporting Information

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Temporal absorption spectra of MO over Ag/AgBr, Mott–Schottky curve of BiOIO3. This material is available free of charge via the Internet at http://pubs.acs.org.

■ AUTHOR INFORMATION Corresponding Author *E-mail: [email protected];

[email protected]

Phone: +86-010-82332247

Notes The authors declare no competing financial interest.

■ ACKNOWLEDGEMENTS This work was jointly supported by the National Natural Science Foundations of China (No. 51672258 and No. 51572246), the Fundamental Research Funds for the Central Universities (2652015296).

■ REFERENCES (1) Kubacka, A.; Fernández-García, M.; Colón. G. Advanced Nanoarchitectures for Solar Photocatalytic Applications. Chem. Rev. 2012, 112, 1555-1614, DOI: 10.1021/cr100454n. (2) Zeng, C.; Huang, H. W.; Dong, F.; Ye, L. Q.; Zhang, T. R.; Zhang, Y. H.; Guo, Y. X.; Liu, C. Y.; Hua, Y. M. Dual Redox Couples Ag/Ag+ and I−/(IO3)− Self-Sacrificed Transformation for Realizing Multiplex Hierarchical Architectures with Universally

22


Page 22 of 49

Page 23 of 49

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Powerful Photocatalytic Performance. Appl. Catal. B 2017, 106, 620-632, DOI: 10.1016/j.apcatb.2016.07.029. (3) Feng, N. D.; Wang, Q.; Zheng, A. M.; Zhang, Z. F.; Fan, J.; Liu, S. B.; Amoureux, J. P.; Deng. F. Understanding the High Photocatalytic Activity of (B, Ag)-Codoped TiO2 under Solar-Light Irradiation with XPS, Solid-State NMR and DFT Calculations. J. Am. Chem. Soc. 2013, 135, 1607-1616, DOI: 10.1021/ja312205c. (4) Li, X.; Yu, J. G.; Jaroniec, M. Hierarchical photocatalysts. Chem. Soc. Rev. 2016, 45, 2603-2636, DOI:10.1039/C5CS00838G. (5) Wang, H. L.; Zhang, L. S.; Chen, Z. G.; Hu, J. Q.; Li, S. J.; Wang, Z. H.; Liu, J. S.; Wang, X. C. Semiconductor Heterojunction Photocatalysts: Design, Construction and Photocatalytic

Performances.

Chem.

Soc.

Rev.

2014,

43,

5234-5244,

DOI:

10.1039/C4CS00126E. (6) Cheng, H. F.; Huang, B. B.; Dai, Y. Engineering BiOX (X=Cl, Br, I) Nanostructures for Highly Efficient Photocatalytic Applications. Nanoscale. 2014, 6, 2009-2026, DOI: 10.1039/C3NR05529A. (7) Huang, H. W.; Han, Xu.; Li, X. W.; Wang, S. C.; Chu, P. K.; Zhang, Y. H. Multiple Heterojunctions Fabrication with Tunable Visible-Light-Active Photocatalytic Reactivity in the BiOBr-BiOI Full Range Composites Based on Microstructure Modulation and Band Structures. ACS Applied Materials & Interfaces. 2015, 7, 482–492, DOI: 10.1021/am5065409.

23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 49

(8) Tian, N.; Zhang, Y. H.; Huang, H. W.; He, Y.; Guo, Y. X. Influences of Gd Substitution on the Crystal Structure and Visible-Light-Driven Photocatalytic Activity of Bi2WO6 Photocatalyst. J. Phys. Chem. C 2014, 118, 15640, DOI: 10.1021/jp500645p. (9) Tian, Y. L.; Chang, B. B.; Lu, J. L.; Fu, J.; Xi, F. N.; Dong, X. P. Hydrothermal Synthesis of Graphitic Carbon Nitride-Bi2WO6 Heterojunctions with Enhanced Visible Light Photocatalytic Activities. ACS Appl. Mater. Interfaces 2013, 5, 7079−7085, DOI: 10.1021/am4013819. (10) Tian, J.; Sang, Y. Y.; Yu, G. W.; Jiang, H. D.; Mu, X. N.; Liu, H. A Bi2WO6-Based Hybrid Photocatalyst with Broad Spectrum Photocatalytic Properties under UV, Visible and

Near-Infrared

Irradiation.

Adv.

Mater.

2013,

25,

5075-5080,

DOI:

10.1002/adma.201302014. (11) Huang, H. W.; Li, X. W.; Wang, J. J.; Dong, F.; Chu, P. K.; Zhang, T. R.; Zhang, Y. H. Anionic Group Self-Doping as a Promising Strategy: Band-Gap Engineering and Multi-Functional Applications of High-Performance CO32- Doped Bi2O2CO3. ACS Catalysis. 2015, 5, 4094−4103, DOI: 10.1021/acscatal.5b00444. (12) Huang, H. W.; He, Y.; Lin, Z. S.; Kang, L.; Zhang, Y. H. Two Novel Bi-Based Borate Photocatalysts: Crystal Structure, Electronic Structure, Photoelectrochemical Properties and Photocatalytic Activity under Simulated Solar Light Irradiation, J. Phys. Chem. C 2013, 117, 22986-22994, DOI: 10.1021/jp4084184. (13) Huang, H. W.; He, Y.; Li, X. W.; Li, M.; Zeng, C.; Dong, F.; Du, X.; Zhang, T. R.; Zhang, Y. H. Non-Centrosymmetric Bi2O2(OH)(NO3) as a Desirable [Bi2O2]2+ Layered 24


Page 25 of 49

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Photocatalyst: Strong Intrinsic Polarity, Rational Band Structure and {001} Active Exposing Facets Co-Benefiting for Robust Photooxidating Capability, J. Mater. Chem. A 2015, 3, 24547–24556, DOI: 10.1039/C5TA07655B. (14) Wang, W. J.; Huang, B. B.; Ma, X. C.; Wang, Z. Y.; Qin, X. Y.; Zhang, X. Y.; Dai, Y.; Whangbo, M. H. Efficient Separation of Photogenerated Electron-Hole Pairs by the Combination of A Heterolayered Structure and Internal Polar Field in Pyroelectric BiOIO3

Nanoplates.

Chem.

Eur.

J.

2013,

19,

14777-14780,

DOI:

10.1002/chem.201302884. (15) Huang, H. W.; He, Y.; He, R.; Jiang, X. X.; Lin, Z. S.; Zhang, Y. H.; Wang, S. C. Novel Bi-based Iodate Photocatalysts with High Photocatalytic Activity. Inorg. Chem. Commun. 2014, 40, 215-219, DOI: 10.1016/j.inoche.2013.12.024. (16) Dong, F.; Xiong, T.; Sun, Y. J.; Zhang, Y. X.; Zhou, Y. Controlling Interfacial Contact and Exposed Facets for Enhancing Photocatalysis via 2D-2D Heterostructure. Chem. Commun. 2015, 51, 8249-8252, DOI: 10.1039/C5CC01993A. (17) Qi, X. M.; Gu, M. L.; Zhu, X. Y.; Wu, J.; Long, H. M.; He, K.; Wu, Q. Fabrication of BiOIO3 Nanosheets with Remarkable Photocatalytic Oxidation Removal for Gaseous Elemental Mercury. Chem. Eng. J. 2016, 285, 11–19, DOI: 10.1016/j.cej.2015.09.055. (18) Huang, H. W.; Tu, S. C.; Zeng, C.; Zhang, T. R.; Reshak, A. H.; Zhang, Y. H.; Macroscopic Polarization Enhancement Promoting Photo- and Piezoelectric-Induced Charge Separation and Molecular Oxygen Activation. Angew. Chem. Int. Edit. 2017, DOI: 10.1002/anie.201706549. 25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 49

(19) Nguyen, S. D.; Yeon, J.; Kim, S. H.; Halasyamani, P. S. A New Polar Oxide Material with a Large SHG Response that Contains Two Lone-Pair Cations and Exhibits An Aurivillius-Type (Bi2O2)2+ Layer. J. Am. Chem. Soc. 2011, 133, 12422-12425, DOI: 10.1021/ja205456b. (20) Wang, W. J.; Cheng, H. F.; Huang, B. B.; Liu, X. L.; Qin, X. Y.; Zhang, X. Y.; Dai, Y. Hydrothermal Synthesis of C3N4/BiOIO3 Heterostructures with Enhanced Photocatalytic Properties. J. Colloid Interface Sci. 2015, 442, 97–102, DOI: 10.1016/j.jcis.2014.11.061. (21) Feng, J. W.; Huang, H. W.; Yu, S. X.; Dong, F.; Zhang, Y. H. A Sself-Sacrifice Template Route to Iodine Modified BiOIO3: Band Gap Engineering and Highly Boosted Visible-Light Active Photoreactivity. Phy. Chem. Chem. Phys. 2016, 18, 7851-7859, DOI: 10.1039/c5cp06685a. (22) Xiong, T.; Zhang, H. J.; Zhang, Y. X.; Dong, F. Ternary Ag/AgCl/BiOIO3 Composites for Enhanced Visible-Light-Driven Photocatalysis. Chin. J. Catal. 2015, 36, 2155–2163, DOI: 10.1016/S1872-2067(15)60980-9. (23) Yu, S. X.; Huang, H. W.; Dong, F.; Li, M.; Tian, N.; Zhang, T. R.; Zhang, Y. H. Synchronously Achieving Plasmonic Bi Metal Deposition and I−Doping by Utilizing BiOIO3 as the Self-Sacrificing Template for High-Performance Multifunctional Applications.

ACS

Appl.

Mater.

Interfaces

2015,

10.1021/acsami.5b09994.

26


7,

27925−27933,

DOI:

Page 27 of 49

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(24) Xia, Y. X.; Lv, K. L.; Tang, D. G.; Li, M. Superiority of Graphene over Carbon Analogs for Enhanced Photocatalytic H2-Production Activity of ZnIn2S4. Appl. Catal. B 2017, 206, 344-352, DOI: 10.1016/j.apcatb.2017.01.060. (25) Long, M. C.; Hu, P. D.; Wu, H. D.; Cai, J.; Tan, B. H.; Zhou, B. X. Efficient Visible Light Photocatalytic Heterostructure of Nonstoichiometric Bismuth Oxyiodide and Iodine Intercalated

Bi2O2CO3.

Appl.

Catal.

B

2016,

184,

20–27,

DOI:

10.1016/j.apcatb.2015.11.025. (26) Sun, L.; Zhang, R. Z.; Wang, Y.; Chen, W. Plasmonic Ag@AgCl Nanotubes Fabricated from Copper Nanowires as High-Performance Visible Light Photocatalyst. ACS Appl. Mater. Interfaces 2014, 6, 14819–14826, DOI: 10.1021/am503345p. (27) Jiang, J.; Zhang, L. Z.; Li, H.; He, W. W.;.Yin, J. J. Self-Doping and Surface Plasmon Modification Induced Visible Light Photocatalysis of BiOCl. Nanoscale. 2013, 5, 10573−10581, DOI: 10.1039/C3NR03597B. (28) Zhu, M. S.; Chen, P. L.; Liu, M. H. Graphene Oxide Enwrapped Ag/AgX (X = Br, Cl) Nanocomposite as A Highly Efficient Visible-Light Plasmonic Photocatalyst. ACS Nano. 2011, 5, 4529−4536, DOI: 10.1021/nn200088x. (29) Yang, Y. C.; Wen, J. W.; Wei, J. H.; Xiong, R.; Shi, J.; Pan, C. X. Polypyrrole-Decorated Ag-TiO2 Nanofibers Exhibiting Enhanced Photocatalytic Activity under Visible-Light Illumination. ACS Appl. Mater.Interfaces 2013, 5, 6201–6207, DOI: 10.1021/am401167y.

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 49

(30) Zeng, C.; Hu, Y. M.; Guo, Y. X.; Zhang, T. R.; Dong, F.; Zhang, Y. H.; Huang, H. W. Facile In Situ Self-Sacrifice Approach to Ternary Hierarchical Architecture Ag/AgX (X = Cl, Br, I)/AgIO3 Distinctively Promoting Visible-Light Photocatalysis with Composition-Dependent Mechanism. ACS Sustainable Chem. Eng. 2016, 4, 3305−3315, DOI: 10.1021/acssuschemeng.6b00348. (31) Ye, L. Q.; Liu, J. Y.; Jiang, Z.; Peng, T. Y.; Zan, L. Facets Coupling of BiOBr-g-C3N4

Composite

Photocatalytic

Activity.

Photocatalyst Appl.

Catal.

Forenhanced B

2013,

Visible-Light-Driven 7,

142-143,

DOI:

10.1016/j.apcatb.2013.04.058. (32) Li, X. D.; Li, M. C.; Cui, P.; Zhao, X.; Gu, T. S.; Yu, H.; Jiang, Y. J.; Song, D. D. Electrodeposition of Ag Nanosheet-Assembled Microsphere@Ag Dendrite Core-Shell Hierarchical Architectures and Their Application in SERS. Cryst. Eng. Com. 2014, 16, 3834-3838, DOI: 10.1039/C3CE41946K. (33) Hu, C.; Guo, J.; Qu, J. H.; Hu, X. X. Photocatalytic Degradation of Pathogenic Bacteria with AgI/TiO2 under Visible Light Irradiation. Langmuir. 2007, 23, 4982–4987, DOI: 10.1021/la063626x. (34) Liu, L.; Ding, L.; Liu, Y. G.; An, W. J.; Lin, S. G.; Liang, Y. H.; Cui, W. Q. A Stable Ag3PO4@PANI Core@Shell Hybrid: Enrichment Photocatalytic Degradation with π-π Conjugation. Appl. Catal. B 2017, 201, 92-104, DOI: 10.1016/j.apcatb.2016.08.005. (35) Huang, H. W.; Zeng, C.; Xiao, K; Zhang, Y. H. Coupling of Solid-Solution and Heterojunction in a 2D-1D Core-Shell-Like BiOCl0.5I0.5/Bi5O7I Hierarchy for Promoting 28


Page 29 of 49

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Full-Spectrum Photocatalysis and Molecular Oxygen Activation. Journal of Colloid and Interface Science. 2017, 504, 257–267. DOI: 10.1016/j.jcis.2017.05.048. (36) Liang, Y. H.; Lin, S. L.; Liu, L.; Hu, J. S.; Cui, W. Q. Oil-In-Water Self-Assembled Ag@AgCl QDs Sensitized Bi2WO6: Enhanced Photocatalytic Degradation Under Visible Light Irradiation. Appl. Catal. B 2015, 164, 192-203. DOI: 10.1016/j.apcatb.2014.08.048. (37) Li, Q. H.; Tang, Q. W.; Du, N.; Qin, Y. C.; Xiao, J.; He, B. L.; Chen, H. Y.; Chu, L. Employment of Ionic Liquid-Imbibed Polymer Gel Electrolyte for Efficient Quasi-Solid-State Dye-Sensitized Solar Cells. J. Power Sources. 2014, 248, 816-821, DOI: 10.1016/j.jpowsour.2013.10.027. (38) Qiao, R.; Mao, M. M.; Hu, E. L.; Zhong, Y. J.; Ning, J. Q.; Hu, Y. Inorg Facile Formation of Mesoporous BiVO4/Ag/AgCl Heterostructured Microspheres with Enhanced Visible-Light Photoactivity. Inorg. Chem. 2015, 54, 9033–9039, DOI: 10.1021/acs.inorgchem.5b01303. (39) Zeng, C.; Hu, Y. M.; Guo, Y. X.; Zhang, T. R.; Dong, F.; Du, X.; Zhang, Y. H.; Huang, H. W. Achieving Tunable Photocatalytic Activity Enhancement by Elaborately Engineering Composition-Adjustable Polynary Heterojunctions Photocatalysts. Appl. Catal. B 2016, 194, 62–73, DOI: 10.1016/j.apcatb.2016.04.036. (40) Dong, F. Li, Q. Y.; Sun, Y.J. Noble Metal-Like Behavior of Plasmonic Bi Particles as A Cocatalyst Deposited on (BiO)2CO3 Microspheres for Efficient Visible Light Photocatalysis. ACS Catal. 2014, 4, 4341−4350, DOI: 10.1021/cs501038q.

29



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(41) Ye, L. Q.; Liu, J. Y.; Gong, C. Q.; Tian, L. H.; Peng, T. Y.; Zan, L. Two Different Roles of Metallic Ag on Ag/AgX/BiOX (X = Cl, Br) Visible Light Photocatalysts: Surface Plasmon Resonance and Z-Scheme Bridge. ACS Catal. 2012, 2, 1677−1683, DOI: 10.1021/cs300213m. (42) Yan, M.; Li, G. L.; Guo, C. S.; Guo, W.; Ding, D. D.; Zhang, S. H.; Liu, S. Q. WO3−x Sensitized TiO2 Spheres with Full-Spectrum-Driven Photocatalytic Activities from UV to Near Infrared. Nanoscale, 2016, 8, 17828-17835, DOI: 10.1039/C6NR06767K. (43) Li, G. L.; Guo, C. S.; Yan, M.; Liu, S. Q. CsxWO3 Nanorods: Realization of Full-Spectrum-Responsive Photocatalytic Activities from UV, Visible to Near-infrared Region. Appl. Catal. B 2016, 183, 142-148, DOI: 10.1016/j.apcatb.2015.10.039. (44) Sang, Y. H.; Zhao, Z. H.; Zhao, M. W.; Hao, P.; Leng, Y. H.; Li, H. From UV to Near-Infrared, WS2 Nanosheet: A Novel Photocatalyst for Full Solar Light Spectrum Photodegradation. Adv. Mater. 2015, 27, 363-369, DOI: 10.1002/adma.201403264.

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Scheme .1 Schematic illustration of fabrication process for the Ag/AgBr/BiOIO3 composites.

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Fig. 1 XRD patterns for BiOIO3, AgBr and Ag/AgBr/BiOIO3 samples.

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Fig. 2 XPS survey spectra (a) and high-resolution XPS spectra for Bi 4f (b), O 1s (c) and Ag 3d (d) of 150%Ag/AgBr/BiOIO3.

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Fig. 3 SEM images for BiOIO3 (a), Ag/AgBr (b), 40%Ag/AgBr/BiOIO3 (c), 150%Ag/AgBr/BiOIO3 (d). Schematic illustration for morphology evolution for BiOIO3, Ag/AgBr , 40%Ag/AgBr/BiOIO3 and 150%Ag/AgBr/BiOIO3 products (e).

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Fig. 4 TEM (a) and HRTEM (b) images of BiOIO3 sample. TEM images of 150%Ag/AgBr/BiOIO3 sample before (c) and after (d) electron beam irradiation. EDX mapping of 150%Ag/AgBr/BiOIO3 (e-h).

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Fig. 5 SEM and EDX images for the 150%Ag/AgBr/BiOIO3 composite.

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Fig. 6 UV-vis diffuse reflectance spectra for the BiOIO3, Ag/AgBr and Ag/AgBr/BiOIO3 composites (a). The determined band gaps of the BiOIO3 and Ag/AgBr (b).

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Fig. 7 Photocatalytic degradation curves of MO (a) and apparent rate constants for degrading MO (b) over the BiOIO3, Ag/AgBr and Ag/AgBr/BiOIO3 composite photocatalysts under UV light illumination. Temporal absorption spectra over BiOIO3 (c) and 150%Ag/AgBr/BiOIO3 (d).

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Fig. 8 Photocatalytic degradation curves of MO (a) and apparent rate constants for degrading MO (b) over the BiOIO3, Ag/AgBr and Ag/AgBr/BiOIO3 composite photocatalysts under visible light illumination. Temporal absorption spectra over BiOIO3 (c), Ag/AgBr (d) and 150%Ag/AgBr/BiOIO3 (e). Photocatalytic degradation curves of 2,4-DCP over the pure BiOIO3, Ag/AgBr and 150%Ag/AgBr/BiOIO3 composite photocatalysts under visible light illumination (f). Temporal absorption spectra of 2,4-DCP over BiOIO3 (g) and Ag/AgBr (h).

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Fig. 9 Temporal absorption spectra of 2,4-DCP (a), phenol (b), BPA (c), tetracycline hydrochloride (d) and chlortetracycline hydrochloride (e) over the 150%Ag/AgBr/BiOIO3 photocatalyst under visible light (λ > 420 nm) irradiation. Degradation efficiency of diverse contaminants under visible light irradiation (f).

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Fig. 10 Photocatalytic degradation efficiency and TOC percentage of BPA over the 150%Ag/AgBr/BiOIO3 heterojunction photocatalyst under visible light illumination.

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Fig. 11 The recycling degradation curves (a) and degradation efficiency (b) for degrading MO over 150%Ag/AgBr/BiOIO3 under visible light illumination. XRD patterns of 150%Ag/AgBr/BiOIO3 before and after photoreaction (c). XPS spectra of 150%Ag/AgBr/BiOIO3 before and after photoreaction (d).

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Fig. 12 Comparison of transient photocurrent responses (a) and EIS Nynquist plots (b) and the proposed equivalent circuit and the fitted values (insets of b) for pure BiOIO3, Ag/AgBr and 150%Ag/AgBr/BiOIO3 under UV-Vis light irradiation. PL spectra of pure BiOIO3, Ag/AgBr and Ag/AgBr/BiOIO3 composites under the excitation of 245nm (c).

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Fig. 13 Photocatalytic degradation of MO over 150%Ag/AgBr/BiOIO3 (a-b), Ag/AgBr (c-d) and BiOIO3 (e-f) samples alone and with different scavengers under irradiation of UV light.

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Fig. 14 Photocatalytic degradation of MO over 150%Ag/AgBr/BiOIO3 (a-b), Ag/AgBr (c-d) and BiOIO3 (e-f) samples alone and with different scavengers under irradiation of visible light (λ > 420 nm).

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Fig. 15 Schematic diagrams for diﬀerent charge-transfer mechanisms of 150%Ag/AgBr/BiOIO3 under the irradiation of UV light (a) and visible light (λ > 420 nm) (b).

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TOC GRAPHIC

Ag/AgBr/BiOIO3 shows UV and visible-light enhanced photocatalytic activity, which has a complete mineralization ability and can decompose diverse antibiotics and industrial contaminants.

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Achieving Enhanced UV and Visible Light Photocatalytic Activity for

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