Self-Assembled 3D Hierarchical Copper Hydroxyphosphate Modified

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Self-assembled 3D hierarchical copper hydroxyphosphate modified by the oxidation of copper foil as recyclable wide wavelength photocatalyst Wen Ling Jiao, Yi Feng Cheng, Jie Zhang, and Renchao Che Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.7b03157 • Publication Date (Web): 07 Nov 2017 Downloaded from http://pubs.acs.org on November 8, 2017

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Self-assembled 3D hierarchical copper hydroxyphosphate modified by the oxidation of copper foil as recyclable wide wavelength photocatalyst

Wenling Jiao†, Yifeng Cheng †, Jie Zhang† and Renchao Che †,* †Advanced Materials Laboratory & Department of Chemistry, Fudan University, Shanghai 200433, People’s Republic of China Corresponding Author *[email protected]

Abstract: In this work, three-dimensional flower-like and petal-like copper hydroxyphosphate Cu5(OH)4(PO4)2 (CHP) based on the self-assembly of numerous nanosheets, have been successfully fabricated on the copper foil by a mild one-pot wet-chemical method without ligand assisted. This research contributes to development of the method to change morphology of CHP active material by varying the degree of substrate oxidation. The two different CHP architectures

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were used to photocatalytically degrade rhodamine 6G (Rh 6G) under solar light, which can absorb wide range light wavelength from UV to near-infrared region (NIR). They all exhibit high photocatalytic activity and good durability, which are potential candidates for high performance and recyclable wide wavelength photocatalysts.

Keywords: 3D architectures; copper hydroxyphosphate; wide wavelength photocatalysis; selfassembly

1 Introduction Sunlight consists of about 48% visible light, so there have been numerous efforts to develop visible light-driven photocatalysts, such as N-doped TiO2 photocatalysts,1,

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photocatalysts,3, 4 and dye-sensitized photocatalysts.5, 6 However, considering the fact that NIR constitutes about 44% of sunlight, therefore developing the photocatalysts, which can convert the light energy from UV to NIR region, is an issue of great importance. Above all, mineral copper hydroxyphosphate is receiving increasingly attention because of its potential application in wide wavelength photocatalysis.7,

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With low cost simultaneously, CHP can degrade organic

pollutants under solar light with a wavelength ranging from UV to NIR region, through generating hydroxyl radicals proved via electron spin resonance (ESR) investigation.10, 11 Cho et al fabricated various 3D hierarchical structures CHP, finding that crystal structure varing with morphology, and the morphology-dependent photocatalytic properties under visible light.7 Wang et al proved that CHP absorbed strongly in the NIR region and degraded 2, 4dichlorophenol effectively due to transfer of photogenerated electrons from the trigonal bipyramidal CuII sites to the adjacent octahedral CuII sites.8


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For CHP photocatalyst, the 3D hierarchical structure with large void spaces are beneficial due to large specific area and facile mass transport.12, 13 To meet the demand, much effort has been devoted to the controllable synthesis of CHP with particular morphologies, including onedimensional (1D) triangular prism,14,

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three-dimensional (3D) walnut-shaped,16 peony-like17

and truncated bipyramidal.18 However, simple and ligand-free fabrication of CHP micro or nanoarchitectures at the microscopic level is still an important challenge. Currently, scientists have reported some researches in fabricating 3D CHP hierarchical structures using different methods (such as wet-chemical,17 surfactant-assisted solvothermal,14, 16 and ionic liquid assisted18 ) and these synthetic processes often required ligand, which hinders photocatalytic degradation of dye pollutants and restricts the wider environmental application of photocatalyst, resulting that they are not suitable for widespread commercial application. Furthermore, without hydrogen peroxide or any other electronic capture agent, existing CHP photocatalytic degradation efficiency is relatively low. Moreover, there remains a common problem that photocatalyst is not easily separated from the reaction solution, cannot be recycled, easy to cause environmental secondary pollution. In recent years, researchers usually combine photocatalyst with magnetic constituent19, 20

or substrates,21, 22, 23, 24 which can achieve effective magnetic separation or direct separation.

For substrate-based photocatalyst, the synthetic process is simple compared with magnetic separation, but the relationships between substrate and active material get little attention. For instance, Bi et al had synthesized tetrahedral Ag3PO4 submicro-crystals on the Ag foil, which showed an efficient visible-light-driven photocatalytic performance.24 However, such research regarding CHP photocatalyst has been rarely reported yet. Hence, the above synthetic methods inspire the rational idea of in situ growing CHP on the Cu foil.25, 26, 27, 28


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Herein, we are innovative to design three-dimensional flower-like and petal-like architectures of CHP on the copper substrates by a mild wet-chemical method without ligand assisted. This approach provides a facile and novel strategy to adjust morphology of active material by controlling the degree of Cu foil oxidation, which contributes to the synthesis of other substratebased photocatalyst. The as-prepared samples showed highly efficient photocatalytic activity and stable recyclability for the degradation of Rh 6G under solar light illumination, which are potential candidates for high performance and recyclable wide wavelength photocatalysts. 2 Experimental section 2.1 Chemicals and materials Copper foils (0.02 mm thick, 99.95%, from Alfa Aesar), sodium phosphate monobasic dehydrate (NaH2PO4·2H2O, AR), hydrogen peroxide (30%), rhodamine 6G (Rh 6G, AR), acetone (AR), nitric acid (68%), anhydrous ethanol (AR) and anhydrous isopropanol (AR) were used as received from Sinopharm Chemical Reagent Company without further purification. All experiments were performed in the laboratory atmosphere and the deionized water (DI water, Millipore) with resistivity greater than 18.0 MΩ·cm was used. 2.2 Synthesis of CHP three-dimensional architectures A typical synthesis of CHP was carried out as follows, modified from the previous report

[17]

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Firstly, a copper foil was cut into pieces (4 × 3 cm2) and cleaned by acetone, isopropanol, dilute nitric acid solution, ethanol and water respectively, to get rid of organic contaminant and oxide layer outside the Cu foil. Subsequently, the bright and cleaned Cu piece was immersed into the 16 ml mixed aqueous solution of NaH2PO4 (0.3 M) immediately. Afterward, 8 mL H2O2 aqueous solution (30%) was added to the mixture drop by drop, and the mixture was standing for approximately 12 hours at room temperature. At last, the impregnated Cu foil covered with light-


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blue layer (morphology was flower-like, macrograph was seen in scheme 1, denoted as F-CHP) was taken out of the solution and the eventually obtained foil was washed by water and ethanol for several times and dried naturally. In order to study the influence of Cu foil oxidation on the morphologies, the Cu foil with partial oxidation was selected to fabricate CHP samples. After cleaning the Cu foil, we exposed it in the air for 10 minutes until its surface became dark and other experimental operation remained unchanged. Eventually, the obtained substrate would be covered with dark-blue layer (morphology was petal-like, macrograph was seen in scheme 1, denoted as P-CHP). 2.3 Characterization X-ray diffraction (XRD) was recorded using a D8 advance (Bruker-AXS) diffractometer, with Cu Kα radiation (λ=1.546 Å) at a scanning rate of 2°/min. X-ray photoelectron spectroscopy (XPS) measurements were carried out on a Thermo VG Scientific ESCALAB 250 spectrometer using monochromated Al Kα excitation. The scanning electron microscope (SEM) images were performed on a field-emission SEM (FESEM, HITAICH, S-4800) worked at 1.0 kV. Highresolution transmission electron microscopy (HRTEM) analysis was carried out on a fieldemission TEM (FE-TEM, JEOL JEM-2100F, Japan) equipped with a post-column Gatan imaging filter system (GIF, Tridium 863, United States) working at 200 kV of the acceleration voltage. The TEM sample was prepared through scraping the CHP film by a plastic tweezers in ethanol accompanied with sonication. Then, the suspension was grinded in a mortar for several times and was dropped on the copper grid. The UV−VIS absorption spectra of Rh 6G solution were examined on an UV/VIS spectrometer (PerkinElmer, Lambda 35). The UV–VIS diffuse reflectance spectra (DRS) was obtained using a Shimadzu UV-3600 spectrometer by using BaSO4 as a reference at room temperature.


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2.4 Photocatalytic experiment All the photocatalytic experiments were performed in a quartz cuvette (1 × 1 × 4 cm, Jingke Optical Instrument, Yixing). Typically, a piece of film (about 0.5 ×3 cm) was cut from the asobtained film and put into the quartz cuvette under the liquid level. Then, 3 mL Rh 6G aqueous solution (10-5 mol/L, pH = 6.47) was poured into the cuvette. To ensure the absorbancedesorption equilibrium between the Rh 6G and film, this cuvette was placed in the dark for one hour before carrying out the photocatalytic experiment. Finally, the quartz cuvette was exposed at room temperature under a Xe lamp (PE300BF, simulated sunlight, 320 nm ≤ λ ≤ 1100 nm, 50 W, MICROSOLAR 300 system, Perfect-Light Company, Beijing) and the lamp height (from the cuvette to the exit window) was measured at 10 cm. Under the photo-control mode of MICROSOLAR300 system, the lamp current was fixed at 13.5 A, ensuring the light intensity near the film was stabilized at about 105.04 mW/cm2. The light intensity was measured by a digital radiodetector (PM100D, THORLABS GmbH, Dachau Germany) and the energy distribution instruction of the lamp (PE300BF) was shown in figure S1. In addition to simulated sunlight irradiation, the Xe lamp light wavelength can be changed by using different bandpass filters (325 nm, 420nm, 450 nm, 500 nm, 550 nm, 650 nm). While different wavelength light through bandpass Filters, their light intensity make a great difference (the light intensity using the six bandpass Filters was measured by digital radiodetectors to shown in Table S1). The UV-VIS absorbance spectra of the Rh 6G solution were tested at selected time intervals. Additionally, the films degraded Rh 6G solution (10-5 mol/L, pH = 6.97) in the same conditions and photocatalytic recyclability was examined by 5 cycles for each one. Before a new cycle of photocatalytic reaction, the film was recycled and then rinsed by ethanol and deionized water for


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several times. In every repeat photocatalytic experiment, all the measurement conditions remained unchanged.

3 Results and discussion 3.1 Structure and morphology

Figure 1 XRD pattern of the as-prepared F-CHP and P-CHP. The X-ray diffraction (XRD) patterns of CHP substrates with two morphologies are shown in figure 1. Notably, two groups of characteristic peaks are basically identical. The peaks fit exactly to the cubic Cu (Fm-3m, PDF# 04-0836) and monoclinic copper hydroxide phosphate (P21/a, PDF# 83-1207), which is consistent with the values in the literature. No other peaks for impurities are observed. The high-intensity and sharp diffraction peaks located at 43.3° , 50.4° and 74.1° are indexed well with the (111), (200) and (220) planes of Cu substrate respectively. Because of the fact that Cu substrate is a main component, the two peaks are so strong that it is hard to observe the peaks assigned to CHP. Fortunately, certain section of XRD pattern can be enlarged zone analysis and the five peaks located at 19.9°, 29.6°, 31.7°, 37.3° and 53.5° are indexed well with the (001), (211), (230), (23-1) and (042) planes of CHP, respectively. Moreover, the HRTEM images of F-CHP (Figure 2d) and P-CHP (Figure 3d) all exhibit clear


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Figure 2 a) and b) The typical SEM images of the as-obtained F-CHP; c) XPS full spectrum of the F-CHP; d) HRTEM image of the F-CHP with an FFT (Fast Fourier Transform) pattern inset. fringes, the spacing agree well with the interplanar spacing of CHP. This is supported by the fast Fourier transform (FFT) pattern (inserted in figure 2d and 3d) and the measured distances of the lattice spacing, 0.53 (0.55) and 0.47 (0.46) nm, could be assigned to the (020) and (120) planes respectively. The samples were further characterized by X-ray photoelectron spectroscopy (XPS) to know more about the composition and the oxidation valence state. Figure 2c and 3c display the XPS full spectra of F-CHP and P-CHP respectively and detailed XPS spectra were shown in figure S2 and S3. There exist the peaks of Cu 2p, O 1s, P 2p and C 1s (as a reference) without other elements peaks. Figure S2d and S3d illustrate the Cu 2p spectra, where two peaks located


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at 933.5 eV and 953.3 eV can be attributed to Cu 2p1/2 and Cu 2p3/2 of Cu2+, respectively. Also the peaks with similar binding energies as the satellite line of Cu2+ are observed. The Cu2+ satellite line of Cu 2p3/2 located at 940.2-945.3eV and Cu 2p1/2 located at 960.0-963.2eV.29, 30, 31 The small peaks for metallic Cu (Cu0) located at 931.9 eV are observed slightly due to XPS data mainly obtain the surface information. The O 1s peak observed at 530.5eV and 534.5eV are indexed to lattice oxygen and absorbed oxygen, respectively (Figure S2c and S3c). The P 2p peak is attributed to P element of PO43-. Simultaneously, the pure Cu films used to synthesize FCHP and P-CHP are characterized by XPS to confirm the oxidation degree (shown in figure 5a). It indicates that Cu0 and Cu2+ phases co-exist in the oxidized Cu film (P-CHP substrate) and for nearly unoxidized Cu film (F-CHP substrate), the Cu 2p spectrum exhibit peaks at the binding energies of 931.5 eV and 950.7 eV obviously which correspond to Cu 2p3/2 and Cu 2p1/2 of metallic Cu (Cu0) respectively.32, 33 The FESEM images of the as-prepared products synthesized by varying the degree of Cu foil oxidation with different magnifications were shown in figure 2, 3 and S4. It is clearly observed that the degree of Cu foil oxidation plays a vital role in controlling the morphology of the final products. Figure 2a and 2b show the morphology of F-CHP employing nearly unoxidized Cu foil. Every CHP microflower grown on the Cu foil is composed of many straight and smooth nanosheets with mean thickness of 90 nm. The self-assembly microflowers show a relatively uniform distribution of diameters (about 100 µm), which stand on the substrate basically and evenly. However, nanosheet-based P-CHP architecture (Figure 3a, 3b) was obtained when selected the Cu foil with partial oxidation as substrate. The analogous nanowall architecture is constructed by the interlaced smooth petals with a wall thickness of 50 nm. The nanosheets in PCHP exhibit thinner and pliable, leading to more closely connected between each other.


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Figure 3 a) and b) The typical SEM images of the as-obtained P-CHP; c) XPS full spectrum of the P-CHP; d) HRTEM image of the P-CHP with an FFT (Fast Fourier Transform) pattern inset. 3.2 Growth mechanisms of the CHP with two morphologies In terms of the FESEM results above, we can find that there are a few similarities in morphology between the two products, which are these 3D architectures all consisted of smooth 2D nanosheets. For F-CHP, the nanosheets are self-assembled into flowers. Interestingly, this self-assembly process is extremely similar with a growth procedure of flowers in nature, from small buds to blooming flowers. Firstly, unoxidized Cu foil surface was oxidized directly by the H2O2 to form Cu2+, resulting in an asperous surface on Cu foil. Until the pH of solution and the concentration of Cu2+ were large enough, the reaction went to the next step. Subsequently, the


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sufficient Cu2+ was combined with the anion HPO42− in the solution to form CHP. It is proposed that this reaction predominantly occurs in the space with the highest concentration of Cu2+, so the crystal precipitates as nucleation and growth locations are grown on the Cu foil surface. Lastly, CHP anisotropically grew into nanosheets and were self-assembled into flowers. In the process, NaH2PO4 can be dissolved to ionize H+ and HPO42−, creating a weakly acidic environment to help H2O2 oxidize copper foil (Cu0). For P-CHP, we select Cu foil oxidized by air partially as reactant. The surface of Cu foil is oxidized to be CuO (CuII) slightly, shown in figure 5a. Because the CuII (CuO) is the highest chemical state of element Cu, it is unable to react with H2O2 oxidant, leading to the reduction of reaction active sites. The decrease of reaction active sites would reduce the growth rate and yield of CHP, which is significant cause for the P-CHP thinner nanosheets and unable to self-assembled into flowers. CHP grew into nanosheets anisotropically and coated on the Cu foil surface by van der waals force layer by layer to form an interleaved petals structure. After the same reaction time, the mass of F-CHP film is slightly bigger than that of P-CHP. The reaction yield of F-CHP and P-CHP (on the Cu substrate) have been estimated by weight. The mass of films before and after reaction is measured by balance respectively and the difference value is the mass of (OH)4(PO4)2. Then, the mass of P-CHP and F-CHP can be calculated by the chemical formula Cu5(OH)4(PO4)2. Because the reaction solution is almost colorless, the amount of Cu2+ into the solution is little and the section is neglectful. Thus, the reaction yield of F-CHP and P-CHP (on the Cu substrate) are estimated to be 10.94 mg and 9.37 mg, respectively. Otherwise, the peak area of the diffraction peak corresponding to the crystal type is proportional to the content of the phase. The peak areas of FCHP and P-CHP are calculated to be 2310.144 and 1917.494 respectively, as shown in supporting information (Figure S5).


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In accordance with the above views, we propose a schematic illustration of the formation mechanism for CHP substrates with two morphologies (Scheme 1).

Scheme 1 Schematic illustration of the formation mechanism for F-CHP and P-CHP. (macrographs were shown in red boxes.)

3.3 Photocatalytic reaction


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In order to know effective active species, three control trials (blank, Cu film and oxidized Cu film) were conducted. When used Cu film or oxidized Cu film as photo catalysts, the dye degradation process is somewhat alike to the blank control experiment. The experimental result demonstrates that the CHP materials are the main active species, as shown in figure 5b. The photocatalytic activity of the CHP substrates with two morphologies have been evaluated through decomposing Rh 6G under simulated sunlight irradiation respectively. Photocatalyst can produce photo-generated electrons/holes by the light irradiation, which diffuse from semiconductor interior to the surface and integrate with H2O/OH- to yield oxidative substances,

Figure 4 a) Time-dependent absorbance spectra of the Rh 6G aqueous solution with P-CHP; (b) The recyclability of the P-CHP in photodegrading Rh 6G; c) Time-dependent absorbance spectra of the Rh 6G aqueous solution with F-CHP; d) The recyclability of the F-CHP in photodegrading Rh 6G.


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such as ·HO and ·O2-. These substances with strong oxidation existed only on the surfaces of photocatalyst. And the dye molecules can be effectively degraded only when it is adsorbed outside catalysts. Therefore, the adsorption capacity of photocatalyst is also an important factor for catalytic efficiency. In dark, the time-dependent Rh 6G concentration changes reveals asprepared materials all exhibit super adsorption performance. The absorption capability of P-CHP for Rh 6G is higher than that of F-CHP in dark, which perhaps confirms the active surface area of P-CHP is larger than F-CHP due to the thinner nanosheets and deposited more evenly. The typical UV-VIS absorption spectra were used to gauge the kinetics of photodegrading Rh 6G aqueous solution (10-5 mol/L) (Figure 4a, 4c). The initial absorption spectrum of Rh 6G shows a strong peak centered at about 526 nm. With the CHP substrates existed, the absorption intensity of Rh 6G solution was decreased gradually under solar light irradiation. According to the law of Lambert-Beer, the absorption is proportional to the concentration of absorber, therefore using At /Ao versus solar light irradiation time can describe the trend of Ct/Co during the photodegradation. The P-CHP aggregate spent 40 minutes to degrade the 97% of Rh 6G solution (10-5 mol/L), whereas the F-CHP aggregate spent 60 minutes to degrade 95% of the solution. Because the same size F-CHP film and P-CHP film have different content of CHP, it is rational to compare their unit mass photocatalytic activity (F-CHP film has 10.94 mg CHP and P-CHP film has 9.37 mg CHP). The plots of Ct mg-1 /Co versus irradiation time (Figure 5c) reflect the degradation rates: V(P-CHP) > V(F-CHP). And the linear plots of -ln(Ct mg-1/Co) versus time (Figure 5d) further confirms the psreudo-first order reaction kinetics,35 with the kinetic parameters (simulated linear slope) k(P-CHP) is 0.0033 and k(F-CHP) is 0.0017. The PCHP possesses more compact morphology and thinner nanosheets (Figure 3a, 3b), which provides more active sites. Furthermore, the thinner nanosheets can shorten the time for photo-


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induced electrons to migrate to the surface, which lead to lower recombination rate of photoinduced e-/h+, resulting in higher photocatalytic activity. In addition, the X-ray scattering signal is contributes more from the copper in the high range because the CHP grew on the surface of copper foil. Hence, the peaks at low angle range (Figure S6) contribute more to typical CHP nanosheets. In terms of the profile of the peaks, P-CHP exhibits broader diffraction peaks than that of F-CHP. Considering that the grain size contributes mostly to the peaks broadening in low angle areas (Figure S6 insetmap), F-CHP should have a larger crystal size than the P-CHP. Meanwhile, if the grain size is smaller, it can expose more photocatalytic activity sites, which

Figure 5 a) Cu 2p XPS spectra of pure Cu films to synthesize F-CHP and P-CHP respectively; b) Time-dependent degradation efficiencies of Rh 6G solutions with different materials; c) Time-dependent degradation efficiencies of Rh 6G solutions with different unit mass CHP photocatalysts; d) The pseudo-first-order kinetic rate plots of Rh 6G solutions with different unit mass CHP photocatalysts. benefits the kinetic effect of photo catalysis procedure.36 The test of degrading Rh 6G had been


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repeated for 5 cycles in the identical conditions to examine the good durability (Figure 4b, 4d). The efficiency with P-CHP photocatalyst under 40min light irradiation can be maintained 92% and with F-CHP photocatalyst under 60min light irradiation can be maintained 87%. The overall mechanical structure of F-CHP aggregate is not as stable as P-CHP, and nanosheets in P-CHP aggregate contact more compactly to form analogous to nanowall structure. After durability tests, F-CHP structure collapsed slightly and P-CHP were stable without apparent change (Figure S7). The activity of photocatalyst is affected by its capability of light absorption and absorption threshold. The DRS measurement of CHP were conducted as shown in figure 6d. The tails of the absorption band can be extended to the NIR zone. The absorption of UV-light region is mainly attributed to the electron transition from valence band to conduction band, visible-light region caused by the surface structure of CHP16 and near-infrared light resulted from the electronic structure of CHP, in which axially elongated CuO4(OH)2 octahedra share their corners with axially compressed CuO4(OH) trigonal bipyramids.8 It is verified that the as-obtained CHP materials are wide wavelength photocatalysts which can enlarge the spectral response and enhance the utilization of sunlight. Owing to the DRS data of the two samples are similar, the band-gap values calculated from the corresponding modified Kubelka-Munk functions have little difference. This lack of a quantum-confinement effect results from the relatively large size of CHP grain.34 With unique structure, CHP can absorb in the wavelength range of 300-800 nm. In order to further research the relationships between their photo activity and light wavelength, we used six bandpass filters (325 nm, 420nm, 450 nm, 500 nm, 550 nm and 650 nm) to control Xe lamp light wavelength. We carried out the photodegradation experiments with P-CHP and F-CHP under different wavelength light irradiation and the materials can utilize UV, visible light and infra


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light to degrade Rh 6G respectively. The results are placed in figure 6a, 6b and supporting information. After the light intensity normalization, the photodegradation efficiency with UV light is the highest, which can degrade Rh 6G (10-5 M) for 300 min with 12 mW/cm2. And the visible light (500 nm) and NIR (650 nm) also exhibit well performance, which can degrade 25% Rh 6G (10-5 M) for 300 min with 12 mW/cm2. Under the same wavelength, P-CHP always has better catalytic performance. For P-CHP and F-CHP, the relationship of wavelength and photo activity is similar. To some extent, there exists a positive correlation between absorption wavelength and photo activity. The as-prepared P-CHP and F-CHP are potential candidates for high performance and recyclable wide wavelength photocatalysts.


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Figure 6 a) Time-dependent degradation efficiencies of Rh 6G solutions with P-CHP under different wavelength light; b) Time-dependent degradation efficiencies of Rh 6G solutions with F-CHP under different wavelength light; c) Degradation efficiencies versus wavelength curve; d) The UV-VIS DRS of F-CHP and P-CHP.

4 Conclusions In summary, we have synthesized the recyclable P-CHP and F-CHP active materials in situ grown on the Cu substrates through controlling the degree of Cu foil oxidation innovatively. Meanwhile, the related growth mechanisms have been proposed in this paper. The as-prepared two materials can absorb wide wavelength light from UV to NIR, which all exhibit good photocatalytic activity. The P-CHP spent 40 minutes to degrade the 97% of Rh 6G solution (10-5


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mol/L), whereas the F-CHP spent 60 minutes to degrade 93% of the solution. After 5 cycles to degrading Rh 6G, there was not obvious decline in performance and damage in morphology.

AUTHOR INFORMATION Corresponding Author *[email protected] Author Contributions R.C. and Y.C. designed research; W.J. performed research, analyzed data and wrote the paper; J.Z. performed XPS tests.

ACKNOWLEDGEMENTS This work was supported by the Ministry of Science and Technology of China (973 Project 2013CB932901; 2016YFE0105700) and the National Natural Science Foundation of China (51672050, 51172047) and NSAF-U1330118.

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Figure 1 XRD pattern of the as-prepared CHP-F and CHP-P. 267x104mm (95 x 95 DPI)


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Figure 2 a) and b) The typical SEM images of the as-obtained CHP-F; c) XPS full spectrum of the CHP-F; d) HRTEM image of the CHP-F with an FFT (Fast Fourier Transform) pattern inset. 400x332mm (72 x 72 DPI)


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Figure 3 a) and b) The typical SEM images of the as-obtained CHP-P; c) XPS full spectrum of the CHP-P; d) HRTEM image of the CHP-P with an FFT (Fast Fourier Transform) pattern inset 400x333mm (72 x 72 DPI)


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Figure 4 a) Time-dependent absorbance spectra of the Rh 6G aqueous solution with P-CHP; (b) The recyclability of the P-CHP in photodegrading Rh 6G; c) Time-dependent absorbance spectra of the Rh 6G aqueous solution with F-CHP; d) The recyclability of the F-CHP in photodegrading Rh 6G. 458x352mm (72 x 72 DPI)


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Scheme 1 Schematic illustration of the formation mechanism for F-CHP and P-CHP. (macrographs were shown in red boxes.) 1005x509mm (72 x 72 DPI)


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Figure 5 a) Cu 2p XPS spectra of pure Cu films to synthesize F-CHP and P-CHP respectively; b) Timedependent degradation efficiencies of Rh 6G solutions with different materials; c) Time-dependent degradation efficiencies of Rh 6G solutions with different unit mass CHP photocatalysts; d) The pseudo-firstorder kinetic rate plots of Rh 6G solutions with different unit mass CHP photocatalysts. 458x352mm (72 x 72 DPI)


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Figure 6 a) Time-dependent degradation efficiencies of Rh 6G solutions with P-CHP under different wavelength light; b) Time-dependent degradation efficiencies of Rh 6G solutions with F-CHP under different wavelength light; c) Degradation efficiencies versus wavelength curve; d) The UV-VIS DRS of F-CHP and P-CHP. 459x350mm (72 x 72 DPI)


Self-Assembled 3D Hierarchical Copper Hydroxyphosphate Modified

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