Polyaniline Hybrid: A Robust and

Article pubs.acs.org/IECR

Nickel-Decorated Graphene Oxide/Polyaniline Hybrid: A Robust and Highly Efficient Heterogeneous Catalyst for Hydrogenation of Terminal Alkynes Vineeta Panwar,†,‡ Arvind Kumar,†,‡ Raghuvir Singh,§ Piyush Gupta,§ Siddharth S. Ray,† and Suman L. Jain*,† †

Chemical Sciences Division and §Analytical Science Division, Council of Scientific and Industrial Research, Indian Institute of Petroleum (CSIR-IIP), Mohkampur, Dehradun 248005, India ABSTRACT: A polyaniline/graphene oxide composite was readily synthesized by liquid−liquid interface polymerization of aniline in the presence of a sulfonated graphene oxide suspension using hydrogen peroxide and iron(III) chloride as oxidants. Subsequently, nickel nanoparticles were decorated on the synthesized hybrid material and used for the hydrogenation of phenylacetylene and its derivatives at room temperature under 100 psi of hydrogen pressure. The synthesized hybrid catalyst showed excellent catalytic activity and was readily recovered by centrifugation at the end of the reaction. The recovered catalyst was successfully used for several runs without any significant loss in the catalytic activity. Importantly, no leaching was observed during this course.

1. INTRODUCTION Graphene is one of the most attractive nanostructures of carbon and has received a tremendous amount of research interest in recent years.1 Because of its large specific surface area, extraordinary thermal and electrical conductivity, and superior electron mobility, graphene is considered to be a promising component for the preparation of composite materials.2,3 Recently, it has received enormous interest in various areas of research, such as biosensors,4,5 bioelectronics,6,7 energy storage and conversion,8,9 and drug delivery and catalysis.10−12 On the other hand, among all conducting polymers, polyaniline (PANI), owing to its low cost, good electrochemical activity, high thermal stability, and environmentally friendly properties, has attracted much scientific interest for supercapacitor applications.13 The hybrid materials based on the combination of graphene and PANI provide a synergistic effect to improve the PANI conductivity and also mitigate the graphene aggregation. These hybrid composites have widely been used for supercapacitor applications; however, they have rarely been used for catalytic applications.14−18 Selective hydrogenation of terminal alkynes to alkenes is an important synthetic transformation because of their widespread applications as important intermediates for organic synthesis.19,20 They are widely used in the chemical industry for large-scale polymerizations21 as well as for other reactions such as metathesis,22 epoxidation,23,24 hydroformylation,25−27 hydroamination,28,29 etc. Conventionally, this reaction is well established using heterogeneous Lindlar catalysts,30 but poor selectivity and the possibility of overreduction are major issues in this process. Furthermore, the replacement of expensive precious metals with low-cost alternatives for hydrogenation reactions is another challenging task. In this regard, a number of homogeneous nonprecious metal complexes have been developed for hydrogenation of alkynes, which owing to their well-defined structures may provide better selectivity control. However, the separation and recycling of homogeneous © 2015 American Chemical Society

transition-metal catalysts still remain scientific challenges of economic and environmental importance. A number of advancements including the development of immobilized metal complexes have been explored to overcome the recycling issues associated with homogeneous metal complexes. Unfortunately, in some instances, these immobilized catalysts are associated with certain drawbacks, such as catalyst instability and metal leaching, during the recycling procedure. Recently, doping of nonprecious metal nanoparticles such as nickel to functionalized supports has been established to be a viable approach to develop an efficient, robust, and leach-proof heterogeneous catalyst for hydrogenation of alkynes. In a continuation to our ongoing research on the development of hybrid catalytic materials for organic transformations, we herein report a simple and efficient synthesis of nickel nanoparticles decorated on a polyaniline/graphene oxide hybrid (SGR/PANI/Ni) and its application in hydrogenation of terminal alkynes to give alkenes selectively (Scheme 1). To the best of our knowledge, this should be the first report on using these hybrid composites for the development of heterogeneous nickel catalysts. Scheme 1. SGR/PANI/Ni-Catalyzed Hydrogenation of Alkynes

Received: Revised: Accepted: Published: 11493

August 7, 2015 October 28, 2015 November 2, 2015 November 2, 2015 DOI: 10.1021/acs.iecr.5b02888 Ind. Eng. Chem. Res. 2015, 54, 11493−11499

Article

Industrial & Engineering Chemistry Research Scheme 2. Schematic Synthesis Route of the SGR/PANI/Ni Hybrid Catalyst

2.3. Synthesis of a SGR/PANI Composite. SGR/PANI composites were synthesized by liquid−liquid interface polymerization. In brief, 175 mg of SGR was sonicated in 150 mL of water, and then 7 mL of a 30% H2O2 solution, 40 mg of FeCl3·6H2O, and 7 mL of a 37% HCl solution were added to the above-dispersed mixture and labeled as aqueous phase I. The nonaqueous phase II part was obtained by dispersing of 6.5 mL of aniline into 150 mL of toluene. Finally, aqueous phase I was added slowly to nonaqueous phase II, and the reaction was performed under cooling conditions (0−10 °C) for 48 h. After polymerization, the product that settled on the aqueous/nonaqueous interface was separated by filtration, washed with water, and dried in an oven at 60 °C overnight. 2.4. Synthesis of SGR/PANI/Ni. SGR/PANI (200 mg) was dispersed in water, and an aqueous solution of nickel chloride (10 wt % of nickel) was added to the dispersed mixture. Hydrazine hydrate was added dropwise to maintain the pH at around 9, and then 0.1 g of NaBH4 was added to the mixture. The reaction was carried out at room temperature for 24 h. The product was filtered, washed with water and acetone several times, and dried at 60 °C in an oven overnight. The weight percent of nickel was found to be 8.14% in the synthesized catalyst, as determined by ICP-AES analysis. The corresponding SGR/Ni was synthesized by following a similar method using SGR in place of the SGR/PANI composite. 2.5. General Experimental Procedure. In to a solution of alkynes (1 mmol) in methanol (10 mL) was added a catalyst (50 mg), and the resulting mixture was placed in an autoclave, maintaining 100 psi of hydrogen pressure. The reaction was stirred at room temperature for 24 h; after completion of the reaction, the catalyst was recovered from the reaction mixture via centrifugation. The resulting mixture was analyzed by GC− MS to obtain the conversion and selectivity of the product. Furthermore, the crude reaction mixture was purified by column chromatography using ethyl acetate/hexane (2:8) as the eluent to obtain the isolated yield of the pure products, as given in Table 2. All of the products are known in the literature and were identified by comparing the GC−MS spectra of the products with a standard Wiley mass spectral library.

2. EXPERIMENTAL SECTION 2.1. Materials and Methods. Graphite flakes, KMnO4, NaNO3, aniline (>99.5%), (3-mercaptopropyl)trimethoxysilane (MPTMS), triethylamine (>99%), iron(III) chloride hydrate, ammonium persulfate, hydrazine, and NaBH4 were purchased from Sigma-Aldrich and used without further purification. Nickel chloride was obtained from Acros Organics. Aqueous ammonia solution, hydrochloric acid, sulfuric acid, aqueous hydrogen peroxide (50 wt %), and other solvents were of analytical grade and were used as received. Distilled water was used throughout the synthesis. The Fourier transform infrared (FTIR) spectra were recorded on a Nicolet 8700 FTIR spectrometer. Powder Xray diffraction (XRD) experiments were performed ona Bruker D8 Advance XRD instrument with Cu Kα radiation. Scanning electron microscopy (SEM) was done using a Quanta 200 F (The Netherlands) field-emission scanning electron microscope at a voltage of 10−30 kV. Thermogravimetric analysis (TGA) was performed using a TA-SDT Q-600 thermal analyzer. Loading of nickel was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES; PS3000UV, Leeman Laboratories). Gas chromatography−mass spectrometry (GC−MS) was carried out by using an HP 5972 mass selective detector coupled with an HP 5890 gas chromatograph. 1H and 13C NMR spectra of the products were recorded at 500 MHz by using a Bruker Avance-III 500 MHz instrument. Hydrogenation reactions were carried out in an autoclave. 2.2. Synthesis of Graphene Oxide (GO) and Sulfonated Graphene (SGR). GO was synthesized from graphite flakes by a modified Hummers method.31 GO was sulfonated by following a two-step procedure according to the literature.32 GO was treated with MPTMS in toluene under refluxing conditions (110 °C) for 24 h. In a subsequent step, mercapto groups grafted onto the GO nanosheets were oxidized by using a 30 wt % H2O2 solution at room temperature for 48 h. The resulting product was washed with ethanol and water to remove the residual precursors and finally dried at 80 °C under vacuum. 11494

DOI: 10.1021/acs.iecr.5b02888 Ind. Eng. Chem. Res. 2015, 54, 11493−11499

Article

Industrial & Engineering Chemistry Research

Figure 1. SEM images of (a) GO, (b) SGR, (c and d) SGR/PANI, and (e and f) SGR/PANI/Ni and EDX graphs of (g) SGR, (h) SGR/PANI, and (i) SGR/PANI/Ni.

3. RESULTS AND DISCUSSION GO was synthesized by a modified Hummers procedure, then treated with MPTMS, and finally oxidized with hydrogen peroxide to obtain SGR. The SGR/PANI composite was synthesized by liquid−liquid interface polymerization in the presence of H2O2 and FeCl3·6H2O as oxidants. Finally, the SGR/PANI/Ni hybrid was synthesized by treating the material with nickel chloride at basic pH. The schematic diagram for synthesis of the SGR/PANI/Ni hybrid catalyst is shown in Scheme 2. A typical SEM image of the sulfonated graphene oxide shows an exfoliated pattern due to the surface functionalization of GO sheets by sulfonated thiosilane moieties (Figure 1a,b). The energy-dispersive X-ray (EDX) graph of SGR clearly illustrates the presence of Si and S atoms, indicating the successful sulfonation of GO sheets. The in situ prepared PANI selfassembled on SGR sheets shows a number of small flowerlike morphologies of polymer chains that can be clearly seen in high-resolution SEM images (Figure 1c,d). After decoration with nickel nanoparticles, the morphology somewhat changed with the appearance of nickel nanoparticle spots, which evidenced the successful synthesis of a ternary hybrid material (Figure 1e,f). Furthermore, the additional peak of nickel in the EDX pattern of the SGR/PANI/Ni hybrid confirmed the presence of nickel in the synthesized hybrid.

The high-resolution transmission electron microscopy (HRTEM) image of SGR/PANI (Figure 2a) clearly indicates the amorphous characteristic of the PANI polymer, which is well-dispersed with sulfonated graphene oxide. In the SGR/ PANI/Ni hybrid, the appearance of agglomerated features indicates the homogeneous dispersion of nickel nanoparticles to the SGR/PANI composite (Figure 2b). Furthermore, the selected-area electron diffraction (SAED) pattern of SGR/ PANI/Ni (Figure 2d) shows some differences in the crystal planes, implying that nickel nanoparticles are fully embedded with the SGR/PANI composite, as evidenced by the SEM images. The FTIR spectra of GO, SGR, SGR/PANI, and SGR/ PANI/Ni are shown in Figure 3. The FTIR spectrum of GO shows a strong absorption band at 1725 cm−1 due to the CO stretching of COOH groups. A sharp band around 1622 cm−1 is attributed to the vibrations of sp2 domains and the residual water. Vibrational bands due to epoxy (C−O; 1220 cm−1) and alkoxy (C−O; 1058 cm−1) groups situated at the edges of the GO nanosheets can also be clearly seen in Figure 3a. After functionalization of GO with MPTMS, the characteristic peaks of CC, Si−O−Si, and Si−O−C bonds are assigned at 1575, 1115, and 1010 cm−1, respectively. The FTIR spectrum of SGR shows some additional peaks at 1240 and 690 cm−1, which are associated with the SO and C−S bonds, respectively, 11495


Article


positions, confirmed the successful loading of nickel nanoparticles on the surface of the SGR/PANI composite. Further, the XRD pattern of GO clearly shows its characteristic diffraction peak at 11.8° with an interlayer distance of 0.74 nm (Figure 4a). After functionalization and

Figure 2. HRTEM images and SAED patterns of (a and c) SGR/ PANI and (b and d) SGR/PANI/Ni.

Figure 4. XRD spectra of (a) GO, (b) SGR, (c) SGR/PANI, and (d) SGR/PANI/Ni catalysts.

sulfonation, the peak of GO disappears and a broad peak at nearly 25° appears, which indicates the complete exfoliation of GO sheets due to surface functionalization (Figure 4b). The amorphous pattern of PANI is observed in XRD spectra of the SGR/PANI composite (Figure 4c). The characteristic diffraction peaks at 45°, 52°, and 75° are assigned to diffraction patterns from the (111), (200), and (220) planes of nickel, confirming the successful loading of nickel in the SGR/PANI composite.33 The thermal degradation pattern of the synthesized materials is shown in Figure 5. The TGA pattern of GO (Figure 5a) shows an initial weight loss at nearly 100 °C, which is mainly due to the adsorbed water molecules in the layered structure of GO. The second significant weight loss is observed in the range of 180−240 °C, corresponding to various oxyfunctionalities on the basal plane and edges of GO. SGR shows some extended thermal stability in comparison to GO, which is mainly due to surface functionalization (Figure 5b). In the case of SGR/ PANI, the continuous weight loss at the higher temperature indicates structural decomposition of PANI, SGR, and SGR/ PANI (Figure 5c). The synthesized SGR/PANI/Ni (Figure 5d) was found to be more stable in comparison to SGR/PANI and degraded at higher temperature because of the high thermal stability of nickel metal. The synthesized SGR/PANI/Ni hybrid was then tested as a heterogeneous catalyst for hydrogenation reactions of alkynes. The experiments were performed in a stainless steel autoclave using 100 psi of hydrogen pressure at room temperature. The initial experiments were performed to optimize the reaction conditions by choosing phenylacetylene as a representative substrate. To evaluate the effect of a solvent, the reaction was performed in different solvents, and the results of these

Figure 3. FTIR spectra of (a) GO, (b) SGR, (c) SGR/PANI, and (d) SGR/PANI/Ni.

indicating the successful oxidation of −SH groups into SO3H groups (Figure 3b).32 Compared with SGR, a number of new peaks attributed to PANI appeared in the spectrum of SGR/ PANI (Figure 3c). The appearance of the quinoid and benzenoid ring vibrations (CC stretching deformations) at about 1575 and 1487 cm−1, respectively, clearly indicates the formation of PANI on the SGR surfaces. In addition, a stretching band assigned to C−N appears at 1298 cm−1, and a band at about 800 cm−1 is attributed to the C−H out-of-plane bending vibrations. The characteristic peak attributed to the N−Q−N−Q stretch of the quinonoid ring appears at around 1241 cm−1, which further indicates that PANI has been covalently grafted onto the surface of the SGR sheets. In the IR spectrum of the SGR/PANI/Ni hybrid, characteristic peaks of the SGR/PANI domain, retained with slight shifting of the peak 11496


Article


increase in the reaction time from 48 to 72 h provided higher conversion, but the byproduct ethylbenzene was obtained along with the desired product styrene (Table 1, entry 7). In order to establish the superiority of the ternary SRG/PANI/Ni hybrid, we also synthesized PANI/Ni and SRG/Ni hybrids and performed the hydrogenation of phenylacetylene under optimized reaction conditions (Table 1, entries 8 and 9). Both hybrids exhibited poor catalytic performance and afforded poor product yield in comparison to the ternary hybrid catalyst. Furthermore, in SGR/Ni and PANI/Ni, agglomeration of polymer chains and leaching of nickel nanoparticles were observed. However, in the developed ternary hybrid catalyst, SGR sheets were used as suitable substrates to anchor PANI chains, which prevented aggregation of SGR through polymeric stabilization and provided a uniform dispersion of nickel nanoparticles. On the basis of these results, we assume that the synergistic effect of each component makes the developed catalyst superior in terms of higher stability and better reactivity. Furthermore, we studied the effect of the temperature by performing the hydrogenation of phenylacetylene at higher temperatures (Table 1, entries 10 and 11). As shown, the higher reaction temperature (50 and 70 °C) affected the selectivity of the desired product adversely. At higher reaction temperature, i.e., 50 °C, the reaction was found to be faster and led to faster conversion of 70% in 12 h but provided poor yield (18% as determined by GC−MS) of the desired alkene (styrene) product. Similarly, further increasing the temperature to 70 °C enhanced the conversion to 90% with very poor yield (10%) of the desired alkene (styrene). On the basis of these studies, we have chosen room temperature as the optimized temperature for this transformation. Subsequently, the catalyst was explored for the hydrogenation of a variety of alkynes in dichloromethane under optimized reaction conditions, and the results of these experiments are summarized in Table 2. As shown, the substituents in the benzene ring did not influence the reaction, and all of the aromatic alkynes were smoothly and efficiently converted to the corresponding alkenes selectively to give moderate to higher yield of the desired product. Aliphatic alkynes (Table 2, entries 6 and 7) also reacted efficiently under the described reaction conditions and afforded moderate yield of the corresponding alkenes. Because the reusability of the heterogeneous catalyst is an important aspect for practical applications, we further tested the recycling of the catalyst for the hydrogenation of phenylacetylene under the described reaction conditions. After completion of the reaction, the catalyst could be easily recovered by filtration, followed by washing with methanol, dried, and reused for subsequent runs. The recovered catalyst was tested for six subsequent runs (Figure 6). As shown, the catalyst showed similar product yields for six subsequent runs, indicating that the developed catalyst was quite stable and can be efficiently reused for several runs without significant loss in the catalytic activity. Furthermore, the metal leaching was studied by ICP-AES analysis of the catalyst before and after the six recycling runs. The nickel content was found to be 7.3% in the fresh catalyst and 7.19% after the six recycling runs, which confirmed negligible nickel leaching. In addition, no nickel metal was detected in the filtrate samples obtained after separation of the catalyst during recycling experiments.

Figure 5. TGA curves of (a) GO, (b) SGR, (c) SGR/PANI, and (d) SGR/PANI/Ni catalysts.

experiments are summarized in Table 1 (entries 1−5). Among the various solvents studied, toluene was found to be ineffective Table 1. Optimization of the Reaction Conditionsa product (%)b entry

solvent

time (h)

1 2 3 4 5 6 7 8 9

toluene isopropyl alcohol methanol water dichloromethane dichloromethane dichloromethane dichloromethane

72 48 48 48 24 12 48 24 24

ethylbenzene

styrene

60 80 80

10 20 20 82 40 86 52c 68d

10

dichloromethane 10

12

52e

18e

12

80f

10f

dichloromethane 11 dichloromethane a

Reaction conditions: phenylacetylene (1 mmol) and catalyst (50 mg) in solvent (10 mL) under a hydrogen pressure of 100 psi at room temperature. bIsolated yield. cUsing SGR/Ni as the catalyst. dUsing PANI/Ni as the catalyst. eThe product yield was determined by GC− MS at 50 °C. fThe product yield was determined by GC−MS at 70 °C.

and gave no reaction under the described experimental conditions. Further, polar solvents such as water, methanol, and isopropyl alcohol were found to be less selective and afforded the corresponding ethylbenzene as the major product. Among all of the solvents, dichloromethane (Table 1, entry 5) was found to be best and afforded the corresponding alkene (styrene) selectively in high yield. On the basis of these results, dichloromethane was chosen as the preferred solvent for further studies. Next, we evaluated the effect of the reaction time on the reaction under the described reaction conditions (Table 1, entries 5−7). The reaction was found to be increased with time and afforded the best results in 24 h; it afforded 82% yield of the styrene selectively without any evidence for the formation of the byproduct ethylbenzene. However, a further 11497


Article

Industrial & Engineering Chemistry Research Table 2. SGR/PANI/Ni-Catalyzed Hydrogenation of Various Alkynesa

a

Reaction conditions: alkyne (1 mmol) and catalyst (50 mg) in dichloromethane (10 mL) under a hydrogen pressure of 100 psi at room temperature for 24 h. bIsolated yield.

■

ACKNOWLEDGMENTS We acknowledge the Director, CSIR-IIP, for his support and encouragement. V.P. and A.K. thank the CSIR and Univeristy Grants Commission, New Delhi, for providing fellowship in the form of Junior and Senior Research Fellowship (JRF/SRF). The authors thank K. L. N. Sivakumar and Rakesh K. Chauhan of CSIR-IIP for providing SEM and AES-ICP results, respectively.

■

(1) Stankovich, S.; Dikin, D. A.; Dommett, G. H. B.; Kohlhaas, K. M.; Zimney, E. J.; Stach, E. A.; Piner, R. D.; Nguyen, S. T.; Ruoff, R. S. Graphene-based composite materials. Nature 2006, 442, 282. (2) Huang, X.; Qi, X.; Boey, F.; Zhang, H. Graphene-based composites. Chem. Soc. Rev. 2012, 41, 666. (3) Dreyer, D. R.; Park, S.; Bielawski, C. W.; Ruoff, R. S. The chemistry of graphene oxide. Chem. Soc. Rev. 2010, 39, 228. (4) Guo, S.; Dong, S. Graphene and its derivative-based sensing materials for analytical devices. J. Mater. Chem. 2011, 21, 18503. (5) Yang, X.; Zhang, X.; Ma, Y.; Huang, Y.; Wang, Y.; Chen, Y. Superparamagnetic graphene oxide−Fe3O4 nanoparticles hybrid for controlled targeted drug carriers. J. Mater. Chem. 2009, 19, 2710. (6) Hong, A. J.; Song, E. B.; Yu, H. S.; Allen, M. J.; Kim, J.; Fowler, J. D.; Wassei, J. K.; Park, Y.; Wang, Y.; Zou, J.; Kaner, R. B.; Weiller, B. H.; Wang, K. L. Graphene flash memory. ACS Nano 2011, 5, 7812. (7) Singh, A. P.; Mishra, M.; Chandra, A.; Dhawan, S. K. Graphene oxide/ferrofluid/cement composites for electromagnetic interference shielding application. Nanotechnology 2011, 22, 465701. (8) Chen, D.; Zhang, H.; Liu, Y.; Li, J. Graphene and its derivatives for the development of solar cells, photoelectrochemical, and photocatalytic applications. Energy Environ. Sci. 2013, 6, 1362. (9) Xiao, J.; Mei, D.; Li, X.; Xu, W.; Wang, D.; Graff, G. L.; Bennett, W. D.; Nie, Z.; Saraf, L. V.; Aksay, I. A.; Liu, J.; Zhang, J. G. Hierarchically porous graphene as a lithium−air battery electrode. Nano Lett. 2011, 11, 5071. (10) Pyun, J. Graphene oxide as catalyst: application of carbon materials beyond nanotechnology. Angew. Chem., Int. Ed. 2011, 50, 46. (11) Han, S. S.; Kim, H.; Park, N. J. Effect of shuttling catalyst on the migration of hydrogen adatoms: A strategy for the facile hydrogenation of graphene. J. Phys. Chem. C 2011, 115, 24696.

Figure 6. Results of the catalytic recycling experiments.

4. CONCLUSION In summary, we have developed a novel SGR/PANI/Ni for the selective hydrogenation of terminal alkynes to the corresponding alkene in moderate-to-good yields. The presence of PANI and SGR in the synthesized hybrid exhibited a synergistic effect and enhanced the catalytic activity of the nickel catalyst for hydrogenation of alkynes. The synthesized catalyst was found to be highly stable and worked efficiently for various runs without loss of activity. Furthermore, the use of a readily available and cost-effective nickel catalyst makes the developed methodology more attractive from environmental and economical viewpoints and also opens new avenues for its use for industrial applications.

■

REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel. 91-135-2525788. Fax: 91-1352660202. Author Contributions ‡

Both authors (V.P. and A.K.) contributed equally.

Notes

The authors declare no competing financial interest. 11498


Article

Industrial & Engineering Chemistry Research (12) Nie, R.; Wang, J.; Wang, L.; Qin, Y.; Chen, P.; Hou, Z. Platinum supported on reduced graphene oxide as a catalyst for hydrogenation of nitroarenes. Carbon 2012, 50, 586. (13) Wang, Y. G.; Li, H. Q.; Xia, Y. Y. Ordered whisker like polyaniline grown on the surface of mesoporous carbon and its electrochemical capacitance performance. Adv. Mater. 2006, 18, 2619. (14) Gómez, H.; Ram, M. K.; Alvi, F.; Villalba, P.; Stefanakos, E.; Kumar, A. Graphene-Conducting Polymer Nanocompositeas Novel Electrode for Supercapacitors. J. Power Sources 2011, 196, 4102. (15) Potts, J. R.; Dreyer, D. R.; Bielawski, C. W.; Ruoff, R. S. Graphene-based polymer nanocomposites. Polymer 2011, 52, 5. (16) Wang, H.; Hao, Q.; Yang, X.; Lu, L.; Wang, X. Graphene Oxide Doped Polyaniline for Supercapacitors. Electrochem. Commun. 2009, 11, 1158. (17) Wang, D. W.; Li, F.; Zhao, J.; Ren, W.; Chen, Z. G.; Tan, J.; Wu, Z. S.; Gentle, I.; Lu, G. Q.; Cheng, H. M. Fabrication of Graphene/ Polyaniline Composite Paper via In Situ Anodic Electropolymerization for High-Performance Flexible Electrode. ACS Nano 2009, 3, 1745. (18) Yan, J.; Wei, T.; Shao, B.; Fan, Z.; Qian, W.; Zhang, M.; Wei, F. Preparation of a Graphene Nanosheet/Polyaniline Compositewith High Specific Capacitance. Carbon 2010, 48, 487. (19) Kluwer, A. M.; Elsevier, C. J. In Handbook for Homogeneous Hydrogenation, 1st ed.; de Vries, J. G., Elsevier, C. J., Eds.; Wiley-VCH: Weinheim, Germany, 2007; Vol. 1, p 375. (20) Ager, D. J. In Handbook for Homogeneous Hydrogenation, 1st ed.; de Vries, J. G., Elsevier, C. J., Eds.; Wiley-VCH: Weinheim, Germany, 2007; Vol. 2, p 745. (21) Scheirs, J.; Priddy, D. B. Modern Styrenic Polymers: Polystyrenes and Styrenic Copolymers; John Wiley: Chichester, U.K., 2003. (22) Ojima, I. Catalytic Asymmetric Synthesis; Wiley-VCH: New York, 2000. (23) Ng, S. S.; Jamison, T. F. Simple alkenes as substitutes for organometallic reagents: nickel-catalyzed, intermolecular coupling of aldehydes, silyl triflates, and alpha olefins. J. Am. Chem. Soc. 2005, 127, 14194. (24) Ho, C. Y.; Ng, S. S.; Jamison, T. F. Nickel-catalyzed, carbonylene-type reactions: Selective for alpha olefins and more efficient with electron-rich aldehydes. J. Am. Chem. Soc. 2006, 128, 5362. (25) Tsuji, J. Palladium Reagents and Catalysts: Innovations in Organic Synthesis; John Wiley & Sons: New York, 1995. (26) Negishi, E-I. Handbook of Organopalladium Chemistry for Organic Synthesis; Wiley-Interscience: New York, 2002. (27) Beletskaya, I. P.; Cheprakov, A. V. The Heck reaction as a sharpening stone of palladium catalysis. Chem. Rev. 2000, 100, 3009. (28) Hills, I. D.; Fu, G. C. Elucidating reactivity differences in palladium-catalyzed coupling processes: the chemistry of palladium hydrides. J. Am. Chem. Soc. 2004, 126, 13178. (29) Ono, K.; Fugami, K.; Tanaka, S.; Tamaru, Y. Palladium catalyzed arylation of N-alkyl O-allyl carbamates: synthesis of cinnamyl alcohols via Heck arylation. Tetrahedron Lett. 1994, 35, 4133. (30) Lindlar, H. Ein neuer Katalysator für selektive hydrierungen. Helv. Chim. Acta 1952, 35, 446. (31) Hummers, W. S.; Offeman, R. E. Preparation of graphitic oxide. J. Am. Chem. Soc. 1958, 80, 1339. (32) Zarrin, H.; Higgins, D.; Jun, Y.; Chen, Z.; Fowler, M. Functionalized graphene oxide nanocomposite membrane for low humidity and high temperature proton exchange membrane fuel cells. J. Phys. Chem. C 2011, 115, 20774. (33) Jiang, Z.; Xie, J.; Jiang, D.; Wei, X.; Chen, M. Modifiers-assisted formation of nickel nanoparticles and their catalytic application to pnitrophenol reduction. CrystEngComm 2013, 15, 560.

11499


Polyaniline Hybrid: A Robust and

Recommend Documents