- Open Access
Copper oxide–graphene oxide nanocomposite: efficient catalyst for hydrogenation of nitroaromatics in water
© The Author(s) 2019
- Received: 20 December 2018
- Accepted: 11 February 2019
- Published: 21 February 2019
A low-cost nanocomposite catalyst containing copper oxide (CuO) nanoparticles (NPs) on graphene oxide (GO) was fabricated by a facile hydrothermal self-assembly process. The segregated CuO NPs and GO exhibited negligible catalytic activities for the reduction of nitroaromatics. However, their hybrid composite accomplished facile reduction with high conversions for several substituted nitroaromatics in aqueous NaBH4 solution; synergetic coupling effect of CuO NPs with GO in the nanocomposite catalyst provided excellent catalytic activity. The nanocomposite catalyst could be separated from the reaction mixture and recycled consecutively.
- Copper oxide
- Graphene oxide
- Synergistic effect
Catalysts play deterministic roles in the hydrogenation of nitroaromatics to aminoaromatics [1–3]. The development of highly active catalysts has attracted remarkable attention for the next-generation green, cost-effective and efficient reduction processes. In particular, the engineered metal nanoparticles (NPs) and nanocomposites have significantly improved the efficiency of catalytic systems. Consequently, various approaches have been utilized to fabricate the inexpensive nanostructured catalysts [4–7]. Varma et al. has emphasized the importance of the greener methods to synthesize nanocomposite catalysts . Virkutyte et al. has reviewed various approaches for the fabrication of stable, environmentally benign, and active metal NPs for catalytic applications . A summary of nanocatalysts utilized for the environmentally friendly reduction of nitroaromatics has also been reviewed by Zhang and colleagues, emphasizing the advantages of the introduced heterogeneous catalysts . However, several drawbacks of the present catalysts need to be circumvented namely enhancing the specific surface area, long-term stability, production cost diminution, and ecological concerns pertaining to their industrial applications [11–14]. To fabricate such catalysts possessing the aforementioned competencies, various nanostructured catalysts have been designed and synthesized [15–17]; metal NPs have been stabilized on variable robust nanostructures, producing active nanocomposite catalysts for reduction of nitroaromatics [18–20]. These heterogeneous catalysts generally comprise precious metal nanocatalysts e.g. Pd, Pt, Rh, Ru etc. to achieve efficient hydrogenation of nitroaromatics [20–22]. However, they are not broadly utilized in the chemical industries due to their high costs which is critical issue from the economical viewpoint . In comparison, earth abundant elements e.g. Cu, Co, Fe, Mn, and Ni are inexpensive and may serve as appropriate catalysts for several catalytic transformations, but with low catalytic activity [24–26]. The nano-sized counterparts of these catalysts also get aggregated quickly in the reaction media due to their high surface-to-volume ratio, limiting their efficiency and reusability [27, 28]. Consequently, engineering hybrid catalysts consist of nanocatalysts integrated susceptible supports is necessary to promote their activities. The nanocomposite catalysts often present improved catalytic properties by exhibiting synergetic effects between the supports and nanocatalysts [29–31].
Graphene has been extensively employed as a stable and excellent nanocatalysts support for synthesizing efficient heterogeneous catalysts [32, 33]; its exceptional conductivity can facilitate the electron transfer during the transformations . Consequently, metal nanocatalysts supported on the graphene may potentially promote the reductants’ electrons donation in the reaction media enhancing the reduction efficiency. Indeed, the synergetic effect between less-reactive nanocatalysts and graphene leads to highly active hybrid nanocomposite catalysts .
Motivated by the aforementioned advantages, we synthesized an efficient nanocomposite catalyst consist of graphene oxide (GO) supported copper oxide NPs (CuO–GO) via a facile hydrothermal self-assembly process for the reduction of nitroaromatics. The CuO–GO nanocomposite catalyst exhibited high yields for the reduction of various nitroaromatics using aqueous sodium borohydride (NaBH4) at room temperature.
2.1 Materials and characterization
Water was deionized by a Nano Pure System (Barnsted). The reagents used in this research were purchased from SigmaAldrich, Samchun, and Daejung and used without any further purification. X-ray photoelectron spectroscopy (XPS) was performed using an Al Kα source (Sigma probe, VG Scientifics) to characterize the surface chemical composition. The nanostructure of the prepared CuO–GO nanocomposite catalyst was studied using a high resolution X-ray diffraction (XRD, D8-Advance), a transmission electron microscope (TEM, JEOL JEM-3010) equipped with an energy-dispersive X-ray spectroscopy (EDX) detector, a scanning TEM (STEM, JEOL JEM-2100F), a thermal gravimetric analysis (TGA, simultaneous DTA/TGA analyzer), Raman technology (LabRAM HV Evolution), and a Fourier Transform-Infrared Radiation spectroscopy (FT-IR, Nicolet iS50). Gas chromatography-mass spectrometry (GC–MS, Agilent Technologies 7693 Autosampler and 5977A Mass selective detector) was employed to monitor the conversion ratio of the nitroaromatics to aminoaromatics.
2.2 Preparation of GO
Graphene oxide was synthesized from graphite using the modified hummer’s approach . Commercial graphite powder (10 g) was added into 230 mL concentrated H2SO4 and cooled to ~ 20 °C with a circulator. 300 g potassium permanganate was added while stirring. Then, the temperature of the reaction was adjusted to 40 °C and the mixture was stirred for 1 h. Water (500 mL) was added to the mixture and the temperature was increased to 100 °C. 2.5 mL H2O2 (30 wt%) was slowly added to the mixture. For purification, the suspension was washed with HCl solution (200 mL) using a filter and a funnel. The suspension was washed with water several times until the filtrate became neutral.
2.3 Preparation of CuO–GO nanocomposite catalyst
CuO–GO nanocomposite catalyst was successfully synthesized using a facile hydrothermal self-assembly process by modifying a previously reported method . CuCl2 (2 mmol) was dissolved in deionized water and mixed with the as-synthesized GO solution (15 mL) and transferred into a clean Teflon-lined container. Thereafter, the Teflon-lined container was filled (70% in volume) with deionized water, placed in an autoclave and tightly sealed, followed by heating up to 150 °C for 12 h. After gradually cooling down, the product was washed with sufficient deionized water and filtered for several times to remove the non- and/or poor-anchored copper oxide NPs on the GO.
2.4 Catalytic reduction of nitroaromatics
The reduction of nitroaromatics to aminoaromatics was carried out using CuO–GO nanocomposite catalyst with aqueous NaBH4 as a reductant at room temperature. In a typical procedure, nanocomposite catalyst (50 mg) was dispersed in deionized H2O (30 mL). Then, a nitroaromatics (1 mmol), NaBH4 (1.2 mmol) and a small stirring bar were added into the reaction glass flask. The reaction mixture was stirred at room temperature for 30 min under air atmosphere. After completion of the reaction, the CuO–GO nanostructured catalyst was separated using a centrifuge. The yields of the aminoaromatics products were measured using a GC–MS. For the reusability evaluation of the nanocomposite catalyst, the separated catalyst was washed with deionized water and dried in an oven for the following runs. The cycling performance was achieved by repeating the above reduction process.
The composition of the nanocomposite catalyst was further confirmed by FT-IR (Fig. 2d). A strong peak at 3450 cm−1 (O–H stretching vibrations) in the case of GO indicates H2O residual compared with CuO–GO nanocomposite catalyst even after sufficient drying. In addition, the characteristic bands of GO are clearly revealed at 1725 cm−1 for C=O stretching vibrations and 1600 cm−1 for C=C (skeletal vibrations of graphene). These peaks disappeared in the CuO–GO nanocomposite catalyst verifying the reduction of GO during the hydrothermal process.
Catalytic comparison study of known heterogeneous catalysts in the reduction of nitrophenol
NH3BH3 (3 mmol)
NaBH4 (1.5 mmol)
NH3BH3 (2 mmol)
H2 (1 MPa)
HCOONH4 (4 mmol)
NaBH4 (1.2 mmol)
NaBH4 (1.2 mmol)
NaBH4 (1.2 mmol)
30 [This work]
Small copper oxide NPs (~ 10 nm) formed nanocomposite with graphene oxide by a facile and cost-efficient hydrothermal self-assembly approach. Although GO and CuO NPs separately showed low catalytic activities in the reduction of nitroaromatics, their composite presented excellent reduction performance with high yield and selectivity for the conversion of various nitroaromatics bearing different functional groups, which can be described by the synergetic effect. In addition, the nanocomposite catalyst could be recycled for up to six uses. This system can be a promising heterogeneous catalyst for the future reduction of nitroaromatics premeditated in large scale wherein the low-cost and facile fabrication are demanded.
All authors contributed to the accomplishment of the project and writing of the manuscript. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
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The authors do not have other results to share as all data are shown in the present article.
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The financial supports of the Future Material Discovery Program (2016M3D1A1027666), and the Basic Science Research Program (2017R1A2B3009135) through the National Research Foundation of Korea are appreciated.
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- T. Zeng, H.Y. Niu, Y.R. Ma, W.H. Li, Y.Q. Cai, Appl. Catal. B-Environ. 134, 26 (2013)View ArticleGoogle Scholar
- M. Shokouhimehr, J.E. Lee, S.I. Han, T. Hyeon, Chem. Commun. 49, 4779 (2013)View ArticleGoogle Scholar
- M. Shokouhimehr, T. Kim, S.W. Jun, K. Shin, Y. Jang, B.H. Kim, J. Kim, T. Hyeon, Appl. Catal. A Gen. 476, 133 (2014)View ArticleGoogle Scholar
- M.B. Gawande, V.D.B. Bonifácio, R. Luque, P.S. Branco, R.S. Varma, Chem. Soc. Rev. 42, 5522 (2013)View ArticleGoogle Scholar
- K.H. Choi, M. Shokouhimehr, Y.S. Kang, D.Y. Chung, Y.H. Chung, M. Ahn, Y.E. Sung, Bull. Korean Chem. Soc. 34, 1195 (2013)View ArticleGoogle Scholar
- V. Polshettiwar, R.S. Varma, Green Chem. 12, 743 (2010)View ArticleGoogle Scholar
- M. Shokouhimehr, M. Shahedi Asl, B. Mazinani, Res. Chem. Intermed. 44, 1617 (2018)View ArticleGoogle Scholar
- R.S. Varma, Curr. Opin. Chem. Eng. 1, 123 (2012)View ArticleGoogle Scholar
- J. Virkutyte, R.S. Varma, Chem. Sci. 2, 837 (2011)View ArticleGoogle Scholar
- K. Zhang, J.M. Suh, J.W. Choi, H.W. Jang, M. Shokouhimehr, R.S. Varma, ACS Omega 4, 483 (2019)View ArticleGoogle Scholar
- Y. Hu, K. Tao, C. Wu, C. Zhou, H. Yin, S. Zhou, J. Phys. Chem. C 117, 8974 (2013)View ArticleGoogle Scholar
- M. Shokouhimehr, J.H. Kim, Y.S. Lee, Synlett 04, 618 (2006)Google Scholar
- J. Hagen, Industrial catalysis: a practical approach (Wiley-VCH, Hoboken, 2006)Google Scholar
- M. Shokouhimehr, Catalysts 5, 534 (2015)View ArticleGoogle Scholar
- R.B. Nasir Baig, R.S. Varma, Green Chem. 15, 398 (2013)View ArticleGoogle Scholar
- O. Verho, K.P.J. Gustaffson, A. Nagendiran, C.W. Tai, J.E. Backvall, ChemCatChem 6, 3153 (2014)View ArticleGoogle Scholar
- Y.M. Lu, H.Z. Zhu, W.G. Li, B. Hu, S.H. Yu, J. Mater. Chem. A 1, 3783 (2013)View ArticleGoogle Scholar
- K. Kuroda, T. Ishida, M. Haruta, J. Mol. Catal. A 298, 7 (2009)View ArticleGoogle Scholar
- Z. Dong, X. Le, X. Li, W. Zhang, C. Dong, J. Ma, Appl. Catal. B 158, 129 (2014)View ArticleGoogle Scholar
- Z. Dong, X. Le, C. Dong, W. Zhang, X. Li, J. Ma, Appl. Catal. B 162, 372 (2015)View ArticleGoogle Scholar
- A. Kim, S. Abdolhosseini, S.M. Rafiaei, M. Shokouhimehr, Energy Environ Focus 4, 18 (2015)View ArticleGoogle Scholar
- I. Lee, J.B. Joo, M. Shokouhimehr, Chin. J. Catal. 36, 1799 (2015)View ArticleGoogle Scholar
- S. He, H. Niu, T. Zeng, S. Wang, Y. Cai, ChemistrySelect 1, 2821 (2016)View ArticleGoogle Scholar
- M. Karthik, P. Suresh, ChemistrySelect 2, 6916 (2017)View ArticleGoogle Scholar
- Y.G. Wu, M. Wen, Q.S. Wu, H. Fang, J. Phys. Chem. C 118, 6307 (2014)View ArticleGoogle Scholar
- B. Tang, W.C. Song, E.C. Yang, X.J. Zhao, RSC Adv. 7, 1531 (2017)View ArticleGoogle Scholar
- N. Zhang, Y.J. Xu, Chem. Mater. 25, 1979 (2013)View ArticleGoogle Scholar
- R.G. Kadam, A.K. Rathi, R. Zboril, R.S. Varma, M.B. Gawande, R.V. Jayaram, ChemPlusChem 82, 467 (2015)View ArticleGoogle Scholar
- Z.S. Wu, S. Yang, Y. Sun, K. Parvez, X. Feng, K. Müllen, J. Am. Chem. Soc. 134, 9082 (2012)View ArticleGoogle Scholar
- Y. Liang, Y. Li, H. Wang, J. Zhou, J. Wang, T. Regier, H. Dai, Nat. Mater. 10, 780 (2011)View ArticleGoogle Scholar
- J. Shi, Chem. Rev. 113, 2139 (2013)View ArticleGoogle Scholar
- S.I. El-Hout, S.M. El-Sheikh, H.M. Hassan, F.A. Harraz, I.A. Ibrahim, E.A. El-Sharkawy, Appl. Catal. A Gen. 503, 176 (2015)View ArticleGoogle Scholar
- Y. Cheng, Y. Fan, Y. Pei, M. Qiao, Catal. Sci. Technol. 5, 3903 (2015)View ArticleGoogle Scholar
- B. Ma, Y. Wang, X. Tong, X. Guo, Z. Zheng, X. Guo, Catal. Sci. Technol. 7, 2805 (2017)Google Scholar
- A. Goswami, A.K. Rathi, C. Aparicio, O. Tomanec, M. Petr, R. Pocklanova, M.B. Gawande, R.S. Varma, R. Zboril, A.C.S. Appl, Mater. Interfaces 9, 2815 (2017)View ArticleGoogle Scholar
- W.S. Hummers, R.E. Offeman, J. Am. Chem. Soc. 80, 1339 (1958)View ArticleGoogle Scholar
- R. Beams, L.G. Cançado, L. Novotny, J. Phys. Condens. Mat. 27, 083002 (2015)View ArticleGoogle Scholar
- C. Sarkar, S.K. Dolui, RSC Adv. 5, 60763 (2015)View ArticleGoogle Scholar
- K.H. Choi, M. Shokouhimehr, Y.E. Sung, Bull. Korean Chem. Soc. 34, 1477 (2013)View ArticleGoogle Scholar
- K. Zhang, K. Hong, J.M. Suh, T.H. Lee, O. Kwon, M. Shokouhimehr, H.W. Jang, Res. Chem. Intermed. 45, 599 (2019)View ArticleGoogle Scholar
- M. Shokouhimehr, K. Hong, T.H. Lee, C.W. Moon, S.-P. Hong, K. Zhang, J.M. Suh, K.S. Choi, R.S. Varma, H.W. Jang, Green Chem. 40, 3809 (2018)View ArticleGoogle Scholar
- S.M. Rafiaei, A. Kim, M. Shokouhimehr, Nanosci. Nanotech. Lett. 6, 309 (2014)View ArticleGoogle Scholar
- M. Shokouhimehr, K.Y. Shin, J.S. Lee, M.J. Hackett, S.W. Jun, M.H. Oh, J. Jang, T. Hyeon, J. Mater. Chem. A 2, 7593 (2014)View ArticleGoogle Scholar
- K.K. Laali, M. Shokouhimehr, Curr. Org. Chem. 6, 193 (2009)Google Scholar
- C.W. Moon, J. Park, S.P. Hong, W. Sohn, D.M. Andoshe, M. Shokouhimehr, H.W. Jang, RSC Adv. 8, 18442 (2018)View ArticleGoogle Scholar