Highly Efficient Organic Photocatalyst with Full Visible Light Spectrum

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Highly efficient organic photocatalyst with full visible light spectra via #-# stacking of TCNQ-PTCDI Zijian Zhang, Jun Wang, Di Liu, Wenjiao Luo, Mo Zhang, Wenjun Jiang, and Yongfa Zhu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b10186 • Publication Date (Web): 12 Oct 2016 Downloaded from http://pubs.acs.org on October 21, 2016

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ACS Applied Materials & Interfaces

Highly efficient organic photocatalyst with full visible light spectra via π-π stacking of TCNQ-PTCDI Zijian Zhang†, Jun Wang†, Di Liu‡, Wenjiao Luo†, Mo Zhang§, Wenjun Jiang† and Yongfa Zhu†* † Department of Chemistry, Tsinghua University, Beijing 100084, China. E-mail: [email protected] ‡ School of chemical &environmental engineering, China University of Mining &Technology, Beijing, P. R. China, 100083 § Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing 100005, China

KEYWORDS. photocatalysis, water oxidation, pollutants degradation, visible light, self-assembly ABSTRACT: The self-assembled TCNQ-PTCDI composited photocatalyst can not only degrade phenol in the rate of 0.154 h-1， which is 10.4 times higher than pure PTCDI; but also produce oxygen in ~14 µmol g-1·h-1 without co-catalysts. The π-π interactions between TCNQ and PTCDI resulted in fast transferring of carriers and reduced the recombination. The interaction lowered valence band and narrowed band gap, thus leading to a stronger oxidizability and a broad spectral response (~730nm). Besides, the existence of TCNQ stabilized the composite for decreasing the accumulation of negative charge, which resulted in an excellent stability of the composite. The high catalytic activity can be utilized potentially in the field of environmental and energy applications.

INTRODUCTION Over the past decades, research about photocatalysis in environment treatment and clean energy production has aroused wide attention. Especially, the inorganic photocatalytic materials which are represented by titanium dioxide and zinc oxide,1 have carried out the commercial production. However, comparing with traditional inorganic photocatalysts, organic photocatalytic material with rich chemical structures, flexible design, low cost and other advantages, is still an unknown world. Depending on a number of organic chemistry reactions, energy levels of molecule (HOMO and LUMO) can be regulated. In this way, energy bands (Valence Band and Conduction Band) of organic semiconductor photocatalyst also are devisable and controllable, whose positions decide the oxidizing (VB) /reducing (CB) abilities and the response to spectrum (Band gap). With research going on, most works about organic photocatalysts focus on metal complex and polymer nowadays. Organometallic complexes construct from ions and organic ligands by coordination bond, where ions work as the main catalytic center and organic ligands sensitize ions to wide spectrum. Strictly, in the view of mechanism, organometallic complex could not be considered as completely organic photocatalytic material. In addition, the complexes often take expensive and toxic ruthenium2 and iridium3 as metal center, poor stability of which would make the ions dissolve out and lead to a heavier pollution. As a result, application of organometallic complex in large scale is limited by above defects. The other type of organic photocatalysts are covalent polymers, such as carbon nitride,4 poly(diphenylbutadiyne),5 poly(ursol)6 and carbazolic framework.7 In these materials, organic compounds completely play the catalytic roles, toxicity and high cost are avoided, but the ability of which to conduct charges is poor. Besides in the catalytic process, vast recombination of photogenerated electron-hole pairs and depolymerization, severely

restrain the further improvement of catalytic activities. Moreover, cumbersome synthesis also increases the difficulties of the widespread applications of these materials. Based on the above, we try to find a new accessible class of eco-friendly organic photocatalyst material which has high catalytic activity, proven effective in charge-transport and excellent structure stability. Perylene tetracarboxylic diimide, PTCDI, a wide-used n-type semiconductor, has attracted much attention due to its out-standing stability, excellent electron affinity and charge carrier migration.8 On the strength of these properties, plenty of applications have been investigated, such as organic field-effect transistors (OFETs),9 solar cells,10 photon harvesting,11 sensors,12 photo switches,13 etc. Another material, 7,7,8,8-Tetracyanoquinodimethane, TCNQ, is regarded as one of the most powerful electron acceptors14 and widely used in charge-transfer (CT) complexes.15 And its electrical,16 magnetic,17 electrochemical18 properties arising from the π-π stacking attracted a huge amount of scientists to presents numbers of works every year. With its conjugative system, TCNQ, interacting with other conjugated materials, such as nanotubes,19 graphene20 and C3N4,21 suggests other different properties. Unfortunately, because of the strong π-π stacking, commercial non-substituted PTCDI shows intrinsic insolubility in most solvents,22 resulting huge difficulties in self-assembling and modifying. Recently, we achieved some breakthroughs with PTCDI: we presented an economic and rapid method in concentrated sulfuric acid to form a self-assembled nano photocatalyst for degradation of organic pollutants under visible light, and explained that π channel and internal electrical fields enhanced the separation and migration of photogenerated electron-hole pairs.23 On the basis, we produced a novel organic TCNQ-PTCDI composited photocatalyst. Both PTCDI and TCNQ have large conjugative π structures, as a result, they may combine ideally by strong π-π stacking interactions. It’s

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gratifying that TCNQ also could be solved by concentrated sulfuric acid which means the rapid assembly method may be suitable. MATERIALS AND METHODS Materials. Perylene tetracarboxylic diimide (PTCDI) and 7,7,8,8-Tetracyanoquinodimethane (TCNQ) were purchased from Sinopharm Chemical Reagent Corp., P. R. China. Sulphuric acid and sodium hydroxide were purchased from Beijing Chemical Works. All the reagents used in this research were commercially available and used without further purification. Synthesis of the TCNQ-PTCDI composites. Keeping the total mass of PTCDI and TCNQ in 200mg, the appropriate amount of PTCDI was put into a PE tube according to the different mass ratio of TCNQ and dissolved with 1mL concentrated sulphuric acid under ultrasonic for 1 hour. The same processing is performed for TCNQ. After that, dark violet and yellow solutions were obtained. Then the two solutions were mixed into a tube under ultrasonic for 1 hour to get a homogeneous solution. The well-mixed solution was dropwise added into 30mL water carefully with stirring, and the pH was adjusted by saturated NaOH solution to neutral. Dark violet products were precipitated and stilled overnight, the product was filtered and dried under 65 ℃ in Vacuum drying oven. In this way, different TCNQ mass ratio composite photocatalysts from 10% to 80% were synthesized. The final product presents charming dark brown with a bit of metal lustre before grind, whose optical photo was presented in Figure S1. Characterizations. The crystallinity of the composites was carried out on a Bruker D8-advance diffractometer under Cu-Kα radiation. The structures and morphologies were examined with LEO-1530 filed emission scanning electron microscope (SEM). The high resolution transmission electron microscopy (HRTEM) images were obtained by a JEM 2010F filed emission gun transmission electron microscope with an accelerating voltage of 200 kV. Atomic force microscopy (AFM) measurements were carried out by using a SPM-9700 scanning probe microscope (Shimadzu Corporation). Fourier transform infrared (FTIR) spectra were carried out using Bruker V70FTIR spectrometer. UV-Vis diffuse reflectance spectroscopy (UV-DRS) was scanned by a Hitachi U-3010 UV-Vis spectrophotometer with BaSO4 as the reference. Raman spectra were obtained with HORIBA JY HR800 confocal microscope Raman spectrometer under an Ar-ion laser (514nm). The photocurrent and electrochemical impedance spectroscopy (EIS) were measured on an electrochemical system (CHI-660B, China). ESR spectra were recorded from the sample mixture, containing spin-trapping probes such as 5,5dimethyl-1-pirroline-N-oxide (DMPO), 2,2,6,6-Tetramethyl-4piperidone (TEMP), or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and products, after exposure to visible light for selected times using an endor spectrometer (JEOL ES-ED3X) at room temperature. X-ray photoelectron spectroscopy (XPS) was performed to estimate the VB position of PTCDI and 50%-TCNQ-PTCDI through a PHI 5300 ESCA system. Photoelectrochemical measurements. For investigating the photoelectrochemical performance of the composites, standard three-electrode cell was employed, with a working electrode(composites), a saturated calomel electrode(SCE) as the reference electrode and a platinum wire as the counter electrode. Na2SO4 was taken as the electrolyte solution. The working electrodes were prepared as follows:5 mg composite

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was suspended in 1 mL pure/deionized water under grinding and ultrasonic. Dark purple slurry was obtained and dip-coated onto an indium tin oxide (ITO) glass electrode. Photocatalytic degradation experiments. The photocatalytic degradation of phenol was conducted under visible light (>420nm). The light source was a 500W Xe lamp with a 420 nm cut-off filter, produced by Institute for Electric Light Sources, whose average light intensity was 35 mW cm-2. In the photocatalytic experiments, 25 mg powder composite photocatalyst was dispersed in an aqueous solution of phenol (50mL, 5ppm). Before the light irradiation, the suspensions were stirred in the dark for 1h to get the absorption-desorption equilibrium. At intervals of 1 hour, 2 mL sample of aliquots were taken and centrifuged. The concentration of phenol was analysed by high performance liquid chromatography (Shimadzu LC-20AT) with UV detector (270nm) and Venusil XBP-C18 (Agela Technologies Inc.) column, the mobile phase consisted of methanol and pure water (55:45 for phenol, 75:25 for 2,4-dichlorophenol and 70:30 for bisphenol A, v/v) at a flow rate of 1 mL min-1. Photocatalytic water-oxidation experiments. The photocatalytic water oxidation reaction was carried out with Labsolar-IIIAG system (PerfectLight, Beijing) in the presence of 0.01 mol·L-1 silver nitrate as an electron acceptor. The photocatalyst powders (50mg) were added into 100mL AgNO3 (aq) in the reaction cell with a magnetic stirrer. The light source was a 500W xenon lamp with a 420 nm cut-off filter. The amount of evolved oxygen was determined using a gas chromatograph (GC7920, TCD, Ar carrier). RESULTS AND DISCUSSION Figure 1 presents photocatalytic activities of the photocatalysts under visible light (>420nm) to degrade organic pollutants and oxidize water for oxygen evolution. Dramatically, the apparent rate constant of degradation for 5ppm phenol is enhanced obviously with increasing TCNQ content, seeing Figure 1a. When the mass ratio reaches 50%, the photocatalyst shows the highest activity in 0.154 h-1， nearly 10.4 times as high as pure PTCDI (0.0148 h-1), which could degrade 90% of phenol (seeing the C/C0 curve in Figure 1b). Compared with some inorganic state-of-the-art photocatalysts, g-C3N421 and Bi2WO6,24 50%-TCNQ-PTCDI also shows the highest photocatalytic activity. But when the ratio is over 50%, the phenoldegradation rate constant decreases notably. Furthermore, the highly efficient 50%-TCNQ-PTCDI could produce oxygen from water without co-catalysts under visible light as showed in Figure 1c. In the first one hour, there is no oxygen without visible light irradiation, after turning light on, the amount of oxygen increases rapidly in the rate of ~14 µmol·g-1·h-1. These results confirm the strong photocatalytic oxidizing ability of the 50%-TCNQ-PTCDI. Besides, the 50%-TCNQ-PTCDI photocatalyst possesses an extensive applicability for degradation of organic pollutants with full visible spectra, which was representatively tested by bisphenol A in the rate of 0.085 h-1 and 2,4-dichloro-phenol in 0.081 h-1, seeing Figure 1d and e. Meanwhile, the action spectra, wavelength-dependent photodegradation with band-pass filter results, which is presented in Figure 1f, suggests the wide response of different wavelengths which cover the whole visible region. The photocatalytic activity interested us why the 50%-TCNQ-PTCDI composite could gain the strongest ability of oxidation, and the activity declined when the mass ration of TCNQ less than or exceeded 50%.


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Figure 1. Photocatalytic activities of TCNQ-PTCDI composited materials. a: apparent rate constant k of TCNQ-PTCDI composite photocatalysts for degradation of 5ppm phenol with different TCNQ mass ratio under visible light (λ>420nm); b: the C/C0 curve in the degrading process of PTCDI, 50%-TCNQ-PTCDI, g-C3N4 and Bi2WO6; c: amount of evolved oxygen in photocatalytic water oxidation with 50%-TCNQ-PTCDI under visible light (λ>420nm); d: degradation on 2,4-dichlorophenol and bisphenol A with 50%-TCNQ-PTCDI under visible light (λ>420nm); e: apparent rate constant k of 50%-TCNQ-PTCDI composite photocatalysts for degradation of 2,4-dichlorophenol and bisphenol A under visible light (λ>420nm); f: The action spectra of 50%-TCNQ-PTCDI, wavelength-dependent phenol degradation with 50%-TCNQ-PTCDI (Band pass filter, 450േ15, 500േ15,…, 650േ15 nm).

From the information of gas adsorption and SEM, these composited materials are non-porous originally, which accumulate to form a mesoporous structure. And according to the statistical results in Figure S2, most of the pores are distributed in the range of less than 25 nm. While, the contents of TCNQ make no obvious and regular difference in surface area, pore volume and pore size, seeing Table S1. The morphology of 50%-TCNQ-PTCDI composite looks like layer-by-layer shale, seeing Figure 2a. With the increase of the TCNQ, the morphology of composites become irregular in SEM images (Figure S3). Taking use of AFM, the thickness of each layer can be detected in range of 0.36 to 3 nm (Figure S4). In the XRD image of 50%-TCNQ-PTCDI (Figure 2b), pure TCNQ and PTCDI counterparts are given in Figure S5 and Figure S6, 120, 220, 320, 200 faces of TCNQ have a strong intensity, with 2θ decreasing ~0.2 degree, which means the increasing of d-spacing. In the presence of TCNQ, PTCDI could not crystallize well to form a long-range ordered structure, as a result, peaks in XRD are widen, mainly including 11.82°(0.74nm), 25.07°(0.35nm), 27.02°(0.33nm). In HRTEM image of 50%TCNQ-PTCDI (Figure 2c), there are a lot of nano crystalline PTCDI areas with ~0.36nm d-spacing and less-10nm diameter, and the direction of lattice fringes are different depending on its region. In the magnified dashed region (Figure 2d), the dspacing ranges from 0.34nm to 0.38nm, which is normally resulted from π-π stacking.25 These structure-related results confirm that the main effort between TCNQ and PTCDI is π-π interaction, and with the synergy of hydrogen bond, PTCDI and TCNQ could assembled into composited semiconductor

photocatalyst, the process can be modeled in Scheme 1. On the other hand, the mean free path of photogenerated carriers is about 10nm, thus less-10nm photocatalyst size is good for photogenerated carriers transferring to the surface and substrate. That is also one of the reasons that

Figure 2. Structure-related results of TCNQ-PTCDI composited materials. a: scanning electron microscope image of 50%-TCNQPTCDI composite; b: X-Ray Diffraction image of 50%-TCNQ-PTCDI; c: high resolution transmission electron microscopy image of 50%-TCNQ-PTCDI; d: the magnified dashed region in c.



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nano-scaled photocatalysts could gain high efficient, who makes photogenerated carriers transfer faster and easier with less recombination chance, compared with micro or macro photocatalysts. Although TCNQ is an excellent electron transferring material and beneficial for charge separation of the TCNQ-PTCDI photocatalyst, too much TCNQ will also shade PTCDI, leading to less photon absorption and lower quantum yield. Thus, there is a balance between charge separation and light absorption, where 50% of TCNQ in mass may the balance point. Less than 50%, TCNQ enhances the electrons transport and induces formation of nanocrystal of PTCDI, resulting increase of catalytic activity; on the contrary, over 50% of TCNQ shading PTCDI, reduces photogenerated electrons and holes, resulting decrease of catalytic activity. As for the nature of mass ratio in 50%, molecular weight of PTCDI is 392.32, so to TCNQ is 204.19, when mass ratio in 1:1, the ration in molar is 1:1.92, nearly 1:2. In other words, a PTCDI molecule combined with two TCNQ molecules by π-π interaction, seeing Scheme 1. Certainly, due to defects in crystallization, composite does not show a strict 1:2 relationships.

Scheme 1. Model diagram of TCNQ-PTCDI π - π stacking assembled structure.

With the out-standing photocatalytic ability, the stability of this π-π stacking self-assembled structure was tested by repeated cycling experiments. As shown in Figure 3, the photocatalyst exhibited an excellent stability. Figure 3a presents the cyclic photodegradation of 5 ppm phenol. The decrease of photocatalytic activity for first cycle is mainly caused by the loss of photocatalyst. Because after experiment, we need centrifuge the solution to separate the photocatalyst out, however, due to the nano-size and excellent dispersibility in water, there always is a large amount of photocatalyst that cannot be completely settled, where the loss of photocatalyst closes to 45%. In order to ensure the rigor and reliability of the data, we do not add any photocatalyst in the follow-up experiment. As a result, there is a heavy decrease of photocatalytic activity after the first cycle. But the follow-up three experiments in similar reaction rate, confirm the cycling performance and stability of the photocatalyst for application in photodegradation. Figure 3b. presents 3 times experiments of water oxidation, the decrease of reaction rate is also due to the loss of photocatalyst. After the cyclic experiments, all the photocatalyst powders were collected, which were analyzed by UV-DRS and XRD, seeing Figure S7 and S8. No significant changes can be observed after the repeated reactions in both UV-DRS and XRD spectra, which prove the excellent stability of the composited photocatalyst. And the widen of peak in XRD, meanings the decrease in grain size caused by stirring and flowing. At the same time, the spectroscopy and electrochemistry properties were investigated. The principal vibration modes of TCNQ in Raman spectra (Figure 4a) for 50%-TCNQ-PTCDI

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at 1208 cm-1 (C=CH bending) and 1603 cm-1 (C=C ring stretching) downshift by about 5 and 10 cm-1 (Raman spectra of pure TCNQ is presented in Figure S9), which might be the result of the increase in the conjugation length.21 The same result can be confirmed by the FTIR spectrum (Figure S10), a peak of conjugate –CN in 2220 cm-1 shows obvious red-shift of about 20 wavenumbers. The shift indicates the decrease of bond strength because of the π-π interaction and the enlarged conjugated system. Besides, in the Raman spectra, after 2250 cm-1, there is a very strong fluorescence peak, demonstrating the recombination of electron-hole pairs in PTCDI,8 which leads to a low quantum efficiency. A direct result is that the catalytic activity under 550nm irradiation is significantly lower than other wavelengths, seeing Figure 1d. However, the intensity of fluorescence decreases obviously with the increasing amount of TCNQ, proving the TCNQ could facilitate the separation of photoinduced electron-hole pairs by a fast electron transport. In the UV-DRS spectra (Figure 4b), with increasing TCNQ content, absorption of TCNQ-PTCDI in the visible region is extended about 30 nm and band structure for charge migration and separation can be optimized,26 indicating ~0.07eV of band narrowing. The band-edge shift is significant, in the case, electrons can be stimulated under lower-energy irradiation, taking full use of the whole spectrum, in comparison to the UV photocatalysts. Meanwhile, the lower excited energy, the less photocorrosion would happen. To confirm the model, the electrochemical impedance spectroscopy (EIS) was obtained. The smaller arc radius on the EIS Nyquist plot of TCNQ-PTCDI with increased TCNQ content under visible light irradiation (Figure 5a) can be observed, the same trend without irradiation is showed in Figure S11, suggesting a more effective separation efficiency of photoinduced electron-hole pairs and a faster charge transfer. And

Figure 3. The cyclic experiments of 50%-TCNQ-PTCDI for 5ppm phenol degradation(a) and water oxidation(b).


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ACS Applied Materials & Interfaces increased TCNQ; b: photocurrent spectroscopy of pure PTCDI and 50%-TCNQ-PTCDI.

Figure 4. Spectroscopy of TCNQ-PTCDI composite. a: Raman spectra of PTCDI , 10%-TCNQ-PTCDI and 50%-TCNQ-PTCDI ; b: UV-DRS spectra of PTCDI, TCNQ and 50%-TCNQ-PTCDI.

Figure 5. Electrochemistry properties of TCNQ-PTCDI composite. a: the electrochemical impedance spectroscopy (EIS) Nyquist plot of TCNQ-PTCDI composites with irradiation (λ>420nm), the smaller arc radius on the EIS Nyquist plot of TCNQ-PTCDI with

the photocurrent (Figure 5b) is enhanced obviously, from ~0.3mA to ~3mA, whose intensity is related to the density of photogenerated charges. Thus, less recombination probability of photogenerated carriers in TCNQ-PTCDI composites can be confirmed. Further, we have investigated the mechanism of photocatalytic oxidation. The process of phenol degradation and intermediates were investigated by HPLC (Figure 6a). The peak at 3.78 min is phenol, whose intensity is decreased after 8h irradiation with photocatalytic reaction. And there are several new peaks at short retention time implying that phenol was oxidized to other intermediates, such as maleic anhydride, dihydroxybenzene, 4,4-dihydroxybiphenyl27 and etc. Figure 6b shows the photodegradation of phenol in the presence of hole scavenger (formic acid, ammonium oxalate), hydroxyl radical scavenger (t-BuOH), electron scavenger (AgNO3) under visible light. The photocatalytic activity of 50%-TCNQ-PTCDI decreases in different extent, which implies that holes and superoxide radical contribute to the photocatalytic reaction. Further, the ESR detection of in-situ active species (Figure 6c and d) note that both 1O2 and •−O2 can be detected after 10 min irradiation, which also contribute to the photocatalytic oxidation. In short, the photogenerated holes, 1O2 and •−O2 are the main active species and govern the photocatalytic oxidizing process. Moreover, photogenerated electrons are transferred from PTCDI to dissolved oxygen through TCNQ, then the dissolved oxygen gains electrons changing into •−O2 and 1 O2 (with holes)28 to oxidize the phenol. The activity of the composite also declines when electron scavenger, AgNO3, is added, which results from the decrease of superoxide radical. What’s more, the photoinduced electrons transfer from the HOMO of PTCDI to the LUMO What’s more, the photoinduced electrons transfer from the HOMO of PTCDI to the LUMO of TCNQ is promoted outstandingly by the charge transfer between PTCDI donor and TCNQ acceptor. Our previous work has proved that H-type ππ stacking of PTCDI could cause the deepening of valence band (HOMO) and narrowing of band gap,23 which came up with a one-dimension fast electrons transferring channel and internal electric field, seeing diagram of the mechanism in Figure 6e. To investigate the electronic structure of the composite, X-ray photoelectron spectroscopy (Figure S12) was obtained, the valance-band electronic structures of PTCDI and 50%-TCNQ-PTCDI are different, the VB position of composite is much deeper in +2.86ev than PTCDI in +2.15ev. The deeper VB position contributes to a stronger oxidation ability of holes for organic pollutants oxidation and water splitting. The water oxidation progress could be explained with three equations as follow: Ag+ + H2O → Ag + H+ + O2 (1) TCNQ + H2O → TCNQ- + H+ + O2 (2) PTCDI + H2O → PTCDI- + H+ + O2 (3) Equation 1. presents the whole reaction in the photocatalytic progress. The rate then declines gradually after long-time irradiation, due to the consuming of silver nitrate. In the presence of TCNQ, photogenerated charge carriers are separated and transferred rapidly, photoinduced electrons are transferred to Ag+ by TCNQ, and more holes are left in PTCDI to oxidize



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Figure 6. Investigation of mechanism. a: HPLC map of initial 5 ppm Phenol (red) and 5 ppm Phenol after 8h photocatalytic degradation 1 •− (blue); b: the photodegradation of phenol in the presence of scavengers; c: ESR detection of O2; d: ESR detection of O2; e: diagram to the mechanism of photocatalytic oxidation.

water. In the condition, with decrease of Ag+, photoinduced electrons could not be expended. With reaction going on, because of a high electron affinity, TCNQ and PTCDI would transform into TCNQ- and PTCDI- anions (Equation 2 and 3), which are accumulated gradually leading to collapse of π-π stacking. As a result, the oxygen evolution rate decreases. CONCLUSIONS Highly efficient TCNQ-PTCDI composited photocatalyst is synthetized by a solution-based self-assembly route in water. π-π interaction works as a significant role in speeding up carriers transferring, decreasing recombination of photogenerated electron-hole pairs and deepening VB position. When PTCDI : TCNQ is 1:2 in molar (1:1 in mass), the photocatalyst come up with the highest activity, which is 10.4 times as high as pure PTCDI for organic pollutants degradation, as well for generating oxygen in the rate of ~14 µmol·g-1·h-1 without cocatalysts. The composite material has good stability and recyclability, with its potentials in environment treatment and clean energy production, it may be a promising photocatalyst in the near future.

ASSOCIATED CONTENT Supporting Information. This material is available free of charge via the Internet at http://pubs.acs.org. Optical photo, SEM, AFM, XRD, Raman spectrum, FTIR spectroscopy, EIS, XPS, Table

AUTHOR INFORMATION Corresponding Author

ACKNOWLEDGMENT This work was partly supported by National Basic Research Program of China (973 Program) (2013CB632403) and National Science Foundation of China (21437003, 21673126, 21621003) and Collaborative Innovation Center for Regional Environmental Quality.

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Highly Efficient Organic Photocatalyst with Full Visible Light Spectrum

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