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Jun 10, 2018 - addition of a small amount of sulphuric acid can not only catalyze dehydrogenation of methanol, but also catalyze the acetal reaction. When the ...

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PAPER Qingzhu Zhang et al. Catalytic mechanism of C–F bond cleavage: insights from QM/MM analysis of fluoroacetate dehalogenase

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ARTICLE

Received 00th January 20xx, Accepted 00th January 20xx DOI: 10.1039/x0xx00000x

Visible light-driven methanol dehydrogenation and convert into 1, 1-dimethoxymethane over non-noble metal photocatalyst under acid condition Yuguang Chao,a,b,c Jianping Lai,c Yong Yang,c Peng Zhou,c Yelong Zhang,c Zijie Mu,c Shiying, Li,a,b Jianfeng, Zheng,*a Zhenping Zhua and Yisheng Tan*a

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Methanol dehydrogenated and converted into 1,1-dimethoxymethane (DMM) was achieved over noble metal-free photocatalyst CdS/Ni2P under visible light. This photocatalytic process for methanol-to-H2 and -1 DMM conversion is efficient and atom economic, the optimal rate and selectivity of DMM is 188.42 mmol g -1 h and 82.93%, respectively. This work supplies a new green approach to the direct efficient conversion of methanol into DMM and provides a promising channel for sustainable bio-methanol applications.

Introduction The increasing demands for energy and concerns of climate change over worldwide, are of great importance to utilize renewable biomass and its derivatives for the production of chemicals and fuels that predominantly depend on fossil 1, 2 resources today. Methanol, which contains 12.6 weight percent of hydrogen, is one of the most important bio-alcohols and a good hydrogen storage medium can be obtained from 3, 4 biomass by fermentation. Bio-methanol can be used as fuel, fuel cell, fuel additive and can act as a versatile platform molecule because of its rich chemistry for the production of numerous chemicals or fuels, such as hydrogen, formaldehyde, 5-10 formic acid, esters, and acetals. As a derivative product of selective methanol oxidation, 1,1-dimethoxymethane (DMM) is gaining attention because of its wide applications in cosmetics, pharmaceuticals, fuel additive and starting material for organic synthesis.11, 12 Particularly, DMM is used in the synthesis of polyoxymethylene dimethyl ether (POMM), which is a more environment-friendly embalming agent replace the currently used formaldehyde knowing for human carcinogen. DMM and POMM are considered as much safer chemicals than methanol

a.

State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, 030001, P. R. China. E-mail: [email protected], [email protected] b. University of Chinese Academy of Sciences, Beijing, 100049, P. R. China. c. Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China Electronic Supplementary Information (ESI) available: Additional data including some experimental methods, XPS spectra, XRD, activity of photocatalytic H2 evolution, data of GC-MS, photocurrent response and photoluminescence (PL) spectra. See DOI: 10.1039/x0xx00000x

when they as alternative fuels for low-temperature fuel cells, 13-16 due to the extremely low volatility and the lower toxicity. Traditionally, converting methanol into DMM proceeds in two steps: Methanol is first selectively oxidized in the gas phase to formaldehyde and then the obtained formaldehyde suffers a liquid phase acetalization of the as-obtained formaldehyde 11, 17-21 with methanol in a second reactor. In this indirect process, except the oxidation step is highly unfriendly to the environment, the process is really complex and strict for equipment. Therefore, the development of a simple green and economical process is urgently demanded. Recently, our group finds that platinum-coated TiO2 nanotubes and nanorods are highly active under UV irradiation for ethanol dehydrogenation coupling into DEE.22, 23 Xu’s group demonstrates that decorating geometry- and size-controlled sub-20 nm Pd nanocubes onto 2D TiO2 nanosheets for simultaneous H2 evolution and 1,1-diethoxyethane production under UV 24 irradiation. However, the higher oxidization potential of TiO2 25 converts methanol into CO2, thereby, TiO2 is not a suitable photocatalyst for methanol acetalization. In addition, the pinch ultraviolet light and expensive noble metal cocatalysts also limit the practical application of photocatalytic acetal reaction. Here, for the first time, we have achieved that visible light-driven methanol dehydrogenation-acetalization and convert into H2 and DMM in one step over noble metal-free hybrid photocatalyst CdS nanorods/Ni2P nanoparticles. The addition of a small amount of sulphuric acid can not only catalyze dehydrogenation of methanol, but also catalyze the + acetal reaction. When the concentration of H is 40 mM, the rate of photocatalytic DMM production can reach 188.42 -1 -1 mmol g h , and the selectivity is about 82.93%. Meanwhile, the addition of sulphuric acid has no corrosion to the glass reactor. It’s an economical green strategy to obtain DMM and

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Experiments

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Materials Thiourea NH2CSNH2, lactic acid, cobalt acetate tetrahydrate C4H6O4·Co·4H2O, ethylenediamine C2H8N2, cobalt chloride CoCl2·6H2O, Cadmium nitrate tetrahydrate Cd(NO3)2·4H2O, and sodium hypophosphite NaH2PO2. All of the above chemical reagents are analytical grades and have not been further purified before being used. The preparation of CdS nanorods 26

CdS nanorods were prepared in a typical solvothermal method. Cd(NO3)2·4H2O (10 mmol) and thiourea (30 mmol) were dissolved in 30 mL ethylenediamine by ultrasonic, following by transfer to a 40 mL Teflon-lined, stainless-steel autoclave, which was later maintained at 160 °C for 48 h into an oven and then allowed to cool to room temperature. The yellow products were washed with distilled water and ethanol for three times to remove the residual ethylenediamine. At last, the as-synthesized CdS nanorods were dried at 60 °C under vacuum for 6 h.

Photocatalytic tests The photocatalytic reactions use a 300W Xe-lamp (PLSSEX300/300UV, Perfectlight Company, Beijing, China) with an ultraviolet cut-off filter (λ≥420 nm). And the experiments of photocatalytic methanol dehydrogenation were performed in a 100 mL Pyrex flask with a flowing system (Ar as a carrier gas) at atmospheric pressure and room temperature, and the opening of the flask was sealed with a silicone rubber stopper. In the Pyrex flask, the 5mg photocatalyst was dispersed in mixed neat methanol (20 mL), and then the above suspension was sonicated for several minutes. The system purged with argon for 30 min before irradiation to keep the reaction system under an anaerobic condition. At a predesigned time, To analysed the content of gas phase products, 10 mL mixed gas products were injected into gas chromatography (Fuli, GC9700, TCD, MS-5A column and Ar as a carrier gas). The liquid phase products was analysed using a gas-chromatograph (GC950 equipped with a flame ionization detector (FID) and Rtx-5 column from Alltech) and a gas chromatograph–mass spectrometer (Shimadzu GCMS-QP2010 with a mass spectrometer and DB-5 ms column from Alltech).

The preparation of CdS/Ni2P sample To synthesize CdS/Ni2P NRs, 200 mg CdS NRs, a calculated amount of yellow phosphorus and Ni(NO3)2﹒6H2O (8 :1) were dispersed in ethylenediamine by ultrasonic. The mixture is then kept for 12 o hours at 140 C in a 50 ml Teflon liner. When the autoclave was cooled to room temperature, the yellow green products were collected and washed with benzene, ethanol, and distilled water several times each. The final products were kept in vacuum at 60 oC for 6 h. The weight percentages of co-catalyst Ni2P in the various samples were 0.5, 1.0, 2.0, 5.0, 10.0. In addition, CdS/MoS2-1wt% and CdS/NiS-1wt% were also prepared (the details are presented in the ESI), CdS/Pt-1wt% was produced by photo-deposition under visible light. Characterization The size and morphology of photocatalysts samples were observed by scanning electron microscopy SEM (JSM, S-7001, operated at 10 kV). TEM and HRTEM images of the photocatalysts were characterized using the JEM-2100F electron microscope (operated at 200 kV, JEOL, Japan). A Shimadzu UV-3600 UV/Vis/NIR spectrophotometer was used to investigate the UV/Vis absorption spectroscopy at room temperature. The photoluminescence (PL) spectra of the solid samples were carried out using a Hitachi FL/F7000 spectrophotometer with an excitation wavelength of 420 nm. To obtain high reproducibility of the spectrums, all the UV/Vis and PL measurements were performed for three parallel samples under the same conditions. X-ray photoelectron spectroscopy (XPS) was measured on a Thermo ESCALAB 250 XPS spectrometer (Al Kα, hν=1486.6 eV). A powder X-ray diffractometer (Miniflex, Rigaku) was utilized to obtain the crystallinities of the photocatalyst samples (Cu-Kα, operating at 40 kV and 15 Ma). The shift of the XPS peak of carbon (C 1s whose binding energy is 284.8 eV) was used to evaluate the effect of catalyst surface charge.

Figure 1 SEM image of CdS/Ni2P (A), TEM images of CdS/Ni2P sample (B,C) and HRTEM image of CdS/Ni2P sample (D); High resolution XPS spectra of Ni 2p (E) and P 2p (F).

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H2 from methanol. To our knowledge, such an efficient heterogeneous photocatalyst for the visible light-driven splitting of alcohol has not been reported to date.

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ARTICLE photocatalysts. Modification at the surface of CdS nanorods with a Ni2P nanopartical was performed by another solvothermal reaction in which Ni(NO3)2﹒6H2O and yellow phosphorous acted as raw materials and ethylenediamine served as solvent (Figure S1). Scan electron microscope (TEM) and Transmission electron microscope (TEM) of the Ni2P/CdS hybrid photocatalysts are provided in Figure 1A and Figure 1B, 1C, respectively, which indicate that a highly uniform 1D CdS NRs with an average diameter of ca. 20–30 nm, and a ca. 10 nm Ni2P nanoparticle was loaded on the surface of 1D CdS nanorods. The high-resolution TEM (HRTEM) image (Figure 1D) shows a lattice spacing of approximately 0.34 nm, which corresponds well with the (002) plane of hexagonal CdS (PDF#411049), and the lattice distances of approximately 0.22 nm is consistent with the hexagonal phase Ni2P (PDF#03-0953)26. However, no obvious diffraction peaks belonging to Ni2P were observed in the X-ray diffraction (XRD) pattern and all reflections showed no significant difference from the CdS NRs (Figure S2), probably due to very strong diffraction peaks of CdS NRs and the relatively small amount of Ni2P dispersed on the surface of the CdS 27-29 NRs . The XPS survey spectrum (Figure S3) shows the existence of Ni, P, Cd, and S elements. And the high resolution XPS

Figure 2 Comparison of the photocatalytic H2 evolution over different samples: CdS/Ni2P-1wt%, CdS/NiS-1wt%, CdS/MoS2-1wt%, CdS/Pt-1wt% and blank CdS nanorods (A); Rate of photocatalytic H2 evolution over CdS/Ni2P samples with different Ni2P loading amount (c(H+)=40 mM).

Photoelectrochemical measurement Photoelectrochemical measurements were performed by employing an electrochemical work station (Chenhua Instrument, CHI 660D, Shanghai, China) with a standard three-electrode system. The working electrodes were prepared as follows: 10 mg photocatalyst was added into the mixed solution of 950uL isopropanol and 50 uL nafion (5 wt%) to make a uniform slurry. Then the slurry was coated onto the surface of FTO glass electrodes. The obtained working electrodes were dried overnight o in a vacuum oven at 60 C. Pt wire acts as a reference electrode and Ag/AgCl (with saturated KCl aqueous solution) acts as a counter electrode. A Xe lamp (with an ultraviolet cut-off filter, λ≥420nm, 300 W) was used as the light source. Na2SO4 aqueous solution (0.5 M) was used as the electrolyte. And we use the linear sweep voltammetry (LSV) technique with a scan rate of 5 mV s−1 to obtain the cathodic polarization curves.

Results and discussions Well crystallized hexagonally structured CdS nanorods prepared 26 according to a previously reported method were employed as

Figure 3 The effect of H+ concentration for DMM and EG (A); Rate of photocatalytic H2 evolution and selectivity of DMM over CdS/Ni 2P-1wt% samples with different proton source (B).

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+

C(H ) (mol/L) 0

H2

CO CH4 0

0

CO2 0.02

Selectivity (%) DMM (CH2OH)2 HCOH 7.79

HCOOH

0

86.84

1*10-2

100.93

0.02 1.32

0

66.28

33.29

0

0

2*10-2

162.71

0.19 1.51

0

71.32

28.25

0

0

3*10-2

232.77

0.23 2.62

0

77.53

22.16

0

0

188.42

0.14 1.35

0

82.93

16.66

0

0

4*10

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Rate of gas generation -1 -1 (mmol g h )

0.58

-2

4.98

spectrum of Cd 3d shows two peaks at Cd 3d5/2 (404.9 eV) and Cd 3d3/2 (411.6 eV), together with the S 2p3/2 (160.9 eV) and S 2p1/2 30, 31 (162.1 eV), which is the typical character of CdS (Figure S4). The high resolution XPS spectrum of Ni 2p3/2 (855.8 eV) and Ni 2p1/2 (874.0 eV) peaks (Figure 1E) and P 2p (Figure 1F) shows one peak at 133.3 eV and were attributed to be Ni2P. The diffuse-reflectance UV-vis absorption spectra of as prepared samples are presented in Figure S5. When the cocatalyst Ni2P was loaded on the surface of CdS NRs, the resultant CdS/Ni2P samples show an obvious enhancement than CdS nanorods over the range of 200-500 nm. And CdS/Ni2P-1wt% sample has the best absorption, as more loading amount will affect the absorption of light. Photocatalysis behaviours of the as synthesized photocatalyst samples were characterized for the dehydrogenation coupling reaction of methanol. We performed photocatalytic reaction in methanol (with different amount sulphuric acid added) in argon atmosphere under visible light irradiation (λ>420nm) at room temperature. The bare CdS nanorods show a relativity low photocatalytic activity during the reaction process, while the

Figure 4 In situ ESR spectra for systems containing CdS/Ni2P catalyst in methanol aqueous solution (40 mM H+) in the presence of DMPO (a spin-trapping agent) with visible light irradiation.

concentration of H is 40 mM, and with trace product being detected in the liquid phase after 6h of irradiation. Co-catalysts are benefit for enhancing methanol dehydrogenation, which is demonstrated in Figure 2A. Catalysis tests show that CdS/Ni2P is highly active than bare CdS, and the order of activity is CdS/Ni2P> CdS/NiS> CdS/MoS2 ≈ CdS/Pt> CdS, which should be attributed the + 28 ability of cocatalyst to reduce H for H2. It should be note that, the noble metal co-catalyst Pt has a poorer activity may due to the poison by the produced by-product CO. The performance of photocatalytic methanol dehydrogenation with different amount Ni2P loaded was also evaluated (Figure 2B), when the loading content of Ni2P is 1 wt%, the H2 production rate reaches an optimal -1 -1 value of up to 188.42 mmol g h , while the excess of cocatalyst is able to reduce the light absorption of CdS and act as recombination 27 centre of photon-generated charge carriers. This result is inaccord + with UV-vis spectrum (Figure S5). As H can not only reduce the oxidation potential of methanol, but also catalyze the acetal 22, 32 + reaction, thereby we have studied the effect of different H concentration on the reaction speed and the selectivity of liquid + product. We regulated the H concentration by adding sulfuric acid in methanol, and the experimental results are presented in Table 1 and Figure S6. When sulphuric acid is added, the dehydrogenation rate of methanol increases rapidly and increases with the increase + + of H concentration. Nevertheless, as the concentration of H is further increased, the rate of hydrogen production tends to be -1 constant, and the rate of hydrogen production is 188.42 mmol g h 1 . It is important to note that when the acid is added, CO and CH4 are produced in the gas products, but the rates are negligible. To investigate the photocatalysts durability in practical applications, the photocatalytic cycling test was performed three times under the same condition (Figure S7). The result shows that, after three cycles, the yield of H2 evolution is about 66.94% relative to the first cycle. The decrease in photocatalytic activity may due to the slight corrosion of CdS in acid condition. Moreover, the comparison of XRD spectra before and after the photocatalytic reaction shows that the crystalline structures of the photocatalyst samples have no significant change, thereby, the corrosion of CdS is not serious (Fig. S8). During the process of photocatalytic H2 evolution, the methanol acts as both reactant and solvent can be converted into value-added 1, 1-dimethoxymethane (DMM) by photocatalysis. The chemical structures of the liquid products have been identified by GC-MS, as shown in Fig. S9 and Figure S10, revealing that the main products in the liquid phase are DMM and glycol (EG). Selectivity is an important parameter in the process of organic synthesis. In this photocatalytic reaction, the concentration of hydrogen ion determines the selectivity of DMM directly. As shown in Figure 3A + and Table 1, with the increase of H concentration, the selectivity also increases obviously, and the selectivity of by product glycol is decreased. Notably, when the acid concentration is 40 mM, the selectivity of DMM can reach 82.93%. This is due to the rapid reaction of formaldehyde with methanol in the acid condition by the product of dehydrogenation of methanol. Interestingly, when + using HCl solution to provide H , the rate of photocatalytic

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Table 1 The rates and selectivities of products with different H+ concentration.

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In addition, the periodic on/off photocurrent response of the as prepared photocatalysts under visible light irradiation (Figure 5A) shows that loading Ni2P nanoparticles dramatically improve photocurrent density of photocatalysts, and the CdS/Ni2P-1wt% sample exhibiting an approximately four-fold enhancement of photocurrent density as compared with bare CdS nanorods. The photoluminescence (PL) spectrum is considered as a powerful technology to characterize the separation of charge carriers. Figure 5B shows that the two distinct emission bands at ca.530 nm and 640 nm, which can be attributed to near-band-edge emission and the excess of sulfur or core defects on the nanorods surfaces, respectively. The PL emission intensity shows a distinct decrease while the co-catalyst Ni2P is loaded. Thereby, above results indicate that the co-catalyst Ni2P can enhance the separation efficiency of the photogenerated electron–hole pairs, resulting in a higher photocatalytic activity. The CdS/Ni2P-1wt% sample exhibits the best performance to separate photogeneration carriers, and this result is in good agreement with photocurrent response and the activity of photocatalysis.

Figure 5 Transient photocurrent responses (A), Photoluminescence spectra with an excitation wavelength of 420 nm (B) of as-prepared samples.

hydrogen production and the selectivity of DMM decreased obviously (Figure 3B). This is due to the hydrolysis of DMM in water is very easy, therefore, the existence of the reverse reaction leads 22, 23 to a decrease at the rate of DMM production. Taking the selectivity of DMM into consideration, the formation rate of H2 is similar to that of DMM, maintaining a rate ratio of 1:1. These data indicated that the formation of DMM in the present photocatalytic process proceeded nearly stoichiometrically following the chemical equation shown below:

Figure 6 shows the probable mechanism of photocatalytic methanol dehydrogenation-acetalization reaction. The energy level of the photo-generated holes of CdS nanorods is around 1.9 V, positives to the oxidation potential of methanol around -0.15 V versus the 3, 33 normal hydrogen electrode. Thereby, it is capable for photogenerated holes to oxidize CH3OH and generate intermediate hydroxyalkyl radical, ·CH2OH. And the radicals are easily oxidized to 34, 35 formaldehyde (CH2O) due to the dynamically unstable property. During the two oxidation steps, two protons are generated and they transfer to surface of Ni2P nanoparticles, follow by reducing for H2 from the electrons residing in conduction band of CdS nanorods. The obtained formaldehyde reacts with methanol rapidly to form DMM under acid condition, thereby, there is no formaldehyde and formic acid was detected, and then, no CO2 released in this process. This process can avoid environmental pollution existing in traditional acid-catalyzed acetalization processes.

3CH OH → CH OCH  H O H The in situ electron spin resonance (ESR) spectrum was used for analysis of captured radicals. Figure 4 shows the ESR spectrum obtained from the CdS/Ni2P-1wt% photocatalytic methanol dehydrogenation coupling reaction by using 5,5-dimethyl-1pyrroline N-oxide (DMPO, 0.05 M) as a radical spin-trapping agent. (The highest peak can be attributed the overlap of catalyst defect peak and radical peak) And the result reveals the generation of the hydroxymethyl radical ⋅ CH2OH (aN=15.6, aH=21.5) in the photocatalytic reaction system, which is consistent with the Wang’ 25 report. The ⋅CH2OH radical should be an intermediate by C−H activation for the formation of formaldehyde (CH2O). Therefore, in

Figure 6 Proposed mechanism for the photocatalytic methanol dehydrogenation and conversion into DMM over CdS/Ni2P photocatalyst

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the process of photocatalytic reaction, methanol is oxidized by photogenation holes to hydroxymethyl radicals, and then further oxidized to formaldehyde.

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Conclusions

15.

In summary, we have demonstrated that visible light-driven methanol dehydrogenation-acetalization and convert into H2 and DMM in one step over noble metal-free hybrid semiconductor photocatalyst CdS/Ni2P for the first time. This process for methanolto-DMM conversion is efficient and atom economic. When the concentration of sulphuric acid is 40 mM, the rate of photocatalytic -1 -1 DMM production can reach 188.42 mmol g h , the selectivity is about 82.93%, and there is almost no CO and CO2 release in this process. This work provides a new green approach to the direct efficient conversion of methanol into DMM and provides a promising channel for sustainable bio-methanol applications.

16. 17. 18. 19 20. 21.

22. 23.

Conflicts of interest

24.

There are no conflicts to declare.

25.

Acknowledgements

26.

We acknowledge funding support from the National Natural Science Foundation of China (91545116, 91645113 and 21573269), Shanxi Province (2015021038 and MC2014-01), the start-up supports from Peking University.

27. 28. 29.

Notes and references 1. 2. 3. 4. 5. 6.

7.

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9. 10. 11. 12. 13. 14.

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J. C. Bauer, G. M. Veith, L. F. Allard, Y. Oyola, S. H. Overbury and S. Dai, ACS Catal., 2012, 2, 2537-2546. X. He and H. Liu, Catal. Today, 2014, 233, 133-139. Z. Liu, Z, Yin, C. Cox, M. Bosman, X. Qian, N. Li, H. Zhao, Y. Du, J. Li, D. G. Nocera, Sci. Adv., 2016, 2,1501425 J. C. Serrano-Ruiz, R. Luque and A. Sepulveda-Escribano, Chem. Soc. Rev., 2011, 40, 5266-5281. Z. Chai, T. T. Zeng, Q. Li, L. Q. Lu, W. J. Xiao and D. Xu, J. Am. Chem. Soc., 2016, 138, 10128-10131. Y. Liu, S. F. Zhao, S. X. Guo, A. M. Bond, J. Zhang, G. Zhu, C. L. Hill and Y. V. Geletii, J. Am. Chem. Soc., 2016, 138, 26172628. A. D. Chowdhury, K. Houben, G. T. Whiting, M. Mokhtar, A. M. Asiri, S. A. Al-Thabaiti, S. N. Basahel, M. Baldus and B. M. Weckhuysen, Angew. Chem. Int. Ed., 2016, 55, 15840-15845. X. Liang, X. Yang, G. Gao, C. Li, Y. Li, W. Zhang, X. Chen, Y. Zhang, B. Zhang, Y. Lei and Q. Shi, J. Catal., 2016, 339, 6876. J. Liu, C. Han, X. Yang, G. Gao, Q. Shi, M. Tong, X. Liang and C. Li, J. Catal., 2016, 333, 162-170. R. Sima, G. Liu, Q. Wang, P. Wu, T. Qin, G. Zeng, X. Chen, Z. Liu and Y. Sun, ChemCatChem, 2017, 9, 1776-1781. K.-a. Thavornprasert, M. Capron, L. Jalowiecki-Duhamel and F. Dumeignil, Catal. Sci. Technol., 2016, 6, 958-970. N. Li, S. Wang, Q. Ren, S. Li and Y. Sun, J. Phys. Chem. C, 2016, 120, 29290-29301. Q. Sun, A. Auroux and J. Shen, J. Catal., 2006, 244, 1-9. D. Devaux, H. Yano, H. Uchida, J.-L. Dubois and M. Watanabe, Electro. Acta, 2011, 56, 1460-1465.

31. 32.

33.

34. 35.

F. Vigier, C. Coutanceau, J. M. Léger and J. L. Dubois, J. Power Sources, 2008, 175, 82-90. R. Chetty and K. Scott, J. Power Sources, 2007, 173, 166171. F. Frusteri, L. Spadaro, C. Beatrice and C. Guido, Chem. Eng. J., 2007, 134, 239-245. G. P. Hagen and M. J. Spangler, US Pat., 2002, 6437195. G. P. Hagen and M. J. Spangler, US Pat., 2000, 6166266. H. Li and M. B. Hall, J. Am. Chem. Soc., 2015, 137, 1233012342. S. Royer, X. Secordel, M. Brandhorst, F. Dumeignil, S. Cristol, C. Dujardin, M. Capron, E. Payen and J. L. Dubois, Chem. Commun., 2008, 865-867. H. Zhang, Y. Wu, L. Li and Z. Zhu, ChemSusChem, 2015, 8, 1226-1231. H. Zhang, W. Zhang, M. Zhao, P. Yang and Z. Zhu, Chem. Commun., 2017, 53, 1518-1521. B. Weng, Q. Quan and Y.-J. Xu, J. Mater. Chem. A, 2016, 4, 18366-18377. S. Xie, Z. Shen, J. Deng, P. Guo, Q. Zhang, H. Zhang, C. Ma, Z. Jiang, J. Cheng, D. Deng and Y. Wang, Nat. Commun., 2018, 9, 1181. Z. Sun, H. Zheng, J. Li and P. Du, Energy Environ. Sci., 2015, 8, 2668-2676. B. Han, S. Liu, N. Zhang, Y.-J. Xu and Z.-R. Tang, Appl. Catal. B: Environ., 2017, 202, 298-304. Y. Chao, J. Zheng, J. Chen, Z. Wang, S. Jia, H. Zhang and Z. Zhu, Catalysis Science & Technology, 2017, 7, 2798-2804. S. Liu, B. Weng, Z. R. Tang and Y. J. Xu, Nanoscale, 2015, 7, 861-866. Z. Yan, X. Yu, A. Han, P. Xu and P. Du, J. Phys. Chem. C, 2014, 118, 22896-22903. Y. Chao, J. Zheng, H. Zhang, F. Li, F. Yan, Y. Tan, Z. Zhu, Chem. Eng. J., 2018, 346, 281-288. T. Simon, N. Bouchonville, M. J. Berr, A. Vaneski, A. Adrovic, D. Volbers, R. Wyrwich, M. Doblinger, A. S. Susha, A. L. Rogach, F. Jackel, J. K. Stolarczyk and J. Feldmann, Nat. Mater., 2014, 13, 1013-1018. M. J. Berr, P. Wagner, S. Fischbach, A. Vaneski, J. Schneider, A. S. Susha, A. L. Rogach, F. Jäckel and J. Feldmann, Appl. Phys. Lett., 2012, 100. A. A. Ismail, L. Robben and D. W. Bahnemann, Chemphyschem, 2011, 12, 982-991. R. Hirschl, J. Catal., 2004, 226, 273-282.

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