Enhanced CO2 capture in Fe3O4-graphene

Enhanced CO2 capture in Fe3O4-graphene nanocomposite by physicochemical adsorption A. K. Mishra and S. Ramaprabhu Citation: Journal of Applied Physics 116, 064306 (2014); doi: 10.1063/1.4892458 View online: http://dx.doi.org/10.1063/1.4892458 View Table of Contents: http://scitation.aip.org/content/aip/journal/jap/116/6?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Superior magnetic, dielectric, and magnetodielectric effects in graphene/ZnCo2O4 nanocomposites J. Appl. Phys. 115, 094306 (2014); 10.1063/1.4867645 Photocatalytic and antibacterial properties of Au-TiO2 nanocomposite on monolayer graphene: From experiment to theory J. Appl. Phys. 114, 204701 (2013); 10.1063/1.4836875 Conversion of CH4/CO2 to syngas over Ni-Co/Al2O3-ZrO2 nanocatalyst synthesized via plasma assisted coimpregnation method: Surface properties and catalytic performance J. Appl. Phys. 114, 094301 (2013); 10.1063/1.4816462 Assembled Fe3O4 nanoparticles on graphene for enhanced electromagnetic wave losses Appl. Phys. Lett. 101, 153108 (2012); 10.1063/1.4758931 PLLA- Fe3O4 nanocomposites AIP Conf. Proc. 1459, 238 (2012); 10.1063/1.4738455

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JOURNAL OF APPLIED PHYSICS 116, 064306 (2014)

Enhanced CO2 capture in Fe3O4-graphene nanocomposite by physicochemical adsorption A. K. Mishra and S. Ramaprabhua) Alternative Energy and Nanotechnology Laboratory (AENL), Nano Functional Materials Technology Centre (NFMTC), Department of Physics, Indian Institute of Technology Madras, Chennai – 600036, India

(Received 17 June 2014; accepted 26 July 2014; published online 13 August 2014) Cost effective and efficient methods for CO2 capture are the need of the hour to render the clean environment in the era of rising energy demand. Here, we report the physicochemical adsorption of carbon dioxide (CO2) in iron oxide decorated graphene nanocomposite at elevated pressures and temperatures. Nanocomposite was prepared by scalable and cost effective technique and its suitability for CO2 capture was studied at elevated pressures (3–13 bar) and temperatures (25–100 C) using Sieverts apparatus. The higher CO2 capture capacities of 60, 35, and 24 mmol g1 were observed at 11 bar pressure and 25, 50, and 100 C, respectively, compared to other studied porous materials. Nature of interaction (Physicochemical adsorption) of CO2 with nanocomposite was identified using Fourier transform infrared spectroscopy. Degassing was C 2014 AIP Publishing LLC. performed to examine the recovery of nanocomposite. V [http://dx.doi.org/10.1063/1.4892458]

I. INTRODUCTION

Increasing usage of carbonaceous fuels for meeting the current energy demand has resulted in excess carbon dioxide (CO2) emission and it is expected that its atmospheric concentration may cross 550 ppm by 2035.1 Efficient carbon capture and sequestration (CCS) technology can be achieved by improving CO2 capture efficiency and reducing its cost. The CCS technology attempts to prevent the release of large quantities of CO2 into the atmosphere from fossil fuel use in power generation and other industries.2 Among the conventional methods including cryogenic distillation, chemical solvent scrubbing, adsorption and separation, adsorption in porous sorbents is considered to be one of the most economical and efficient approaches. Activated carbons (ACs), zeolites, molecular sieves, metal organic frameworks (MOFs) and templated carbon adsorbents along with their surface modifications are widely reported for CO2 capture from different process streams.3–9 ACs generally show higher capacity than zeolites at pressures above atmospheric pressure and are often preferred over zeolites because of their relatively moderate strengths of adsorption for gases, which facilitates easier desorption.10–12 ACs indicate CO2 adsorption in the range 5–25 mmol g1 at room temperature and 12–35 bar pressures.13,14 Under similar pressure and temperature conditions, zeolites and other porous materials shows low adsorption capacity in the range 3–5 mmol g1.11,15,16 Chemical interaction of CO2 with metal oxides (CaO, MgO, etc.), lithium zirconates, hydrotalcites, barium and strontium titanates, etc. has also been examined.17–19 Carbon based nanostructures like carbon nanotubes, graphene can act as adsorbents for CO2 due to their high surface area and porosity.20,21 Our earlier reports indicates high degree of CO2 capture in multiwalled a)

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0021-8979/2014/116(6)/064306/5/$30.00

carbon nanotubes and its nanocomposites.22,23 We have also shown the better CO2 capture performance of graphene compared to nanotubes.24 However, carbon nanotubes based nanocomposite are costly and adsorption capacity of graphene largely depends on surface area and pore size distribution and hence, synthesis process. Capture capacity of graphene decreases sharply at higher temperatures due to easier desorption of physically adsorbed gas. As the exhaust of industries, such as automobile, steel and cement industries, thermal power plants may exist at high temperatures, sustainability of CO2 capture capacity is one of the major concerns. Graphene based nanocomposites can be worthy candidates to overcome such problem. In this regard, we have decorated the surface of graphene sheets with nanocrystalline iron oxide (Fe3O4) particles and demonstrated the higher adsorption capacity of resulted nanocomposite even at elevated temperatures. In the present work, high pressure CO2 adsorption study is performed with Sieverts apparatus at three different temperatures 25, 50, and 100 C and the nature of interaction is confirmed using Fourier transform infrared (FTIR) spectroscopy. Recovery of material has been examined by degassing the adsorbed CO2 from nanocomposite at 150 C in a vacuum of 109 bar. II. EXPERIMENTAL SECTION A. Nanocomposite synthesis and characterization

Iron oxide decorated graphene (Fe3O4-HEG) nanocomposite was prepared in two steps. In initial step, graphene was synthesized by hydrogen induced thermal exfoliation of graphite oxide at 200 C,24 prepared by oxidation of graphite (Sigma Aldrich, USA) using Hummer’s method.25 As prepared graphene sheets was named as hydrogen exfoliated graphene (HEG). In second step, nanocrystalline Fe3O4 particles were decorated over HEG by chemical route using

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A. K. Mishra and S. Ramaprabhu

FeCl3.6H2O, FeSO4.7H2O and ammonia solution (Across Organics) as published elswhere.26 Surface morphology was studied using FEI Quanta 200 Scanning Electron Microscope (SEM) with energy dispersive X-ray (EDX) system, while structural morphology by Technai G20 Transmission Electron Microscope (TEM) at the voltage of 200 kV in high vacuum of 1011 bar. The crystalline nature of Fe3O4-HEG was examined by X-ray diffraction (XRD) using X’pert PRO, PANalytical diffractometer ˚ ). X-ray phowith nickel-filtered Cu Ka radiation (k ¼ 1.54 A toelectron spectroscopy (XPS) analysis was performed to confirm the magnetite phase in nanocomposite using an Omicrometer nanotechnology X-ray photoelectron spectrometer. Vibrational characteristic was examined by Perkin Elmer Spectrum1 FTIR instrument. Porous nature of nanocomposite was studied using Micromeritics ASAP 2020 analyser by out gassing the sample at 150 C for 12 h.

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the reversibility of CO2 capture capacity and recovery of nanocomposite. III. RESULTS AND DISCUSSION A. Morphology study

SEM and TEM images of Fe3O4-HEG nanocomposite are given in Figs. 1(a) and 1(b), respectively. Figure 1(a) shows the surface morphology of the nanocomposite indicating differently oriented graphene sheets decorated with Fe3O4 nanoparticles over the surface. Figure 1(b) shows the structural morphology indicating nearly uniform distribution of Fe3O4 nanoparticles over graphene sheets. Figure 1(c) shows the EDX analysis indicating the presence of Fe, C, and O elements suggesting the purity of Fe3O4-HEG. Figure 1(d) depicts the histogram of EDX analysis suggesting the average loading of Fe3O4 nanoparticles around 25 wt. % in nanocomposite.

B. Adsorption-desorption experiment

Measurement of CO2 capture capacity of Fe3O4-HEG was studied using high pressure Sieverts apparatus.22 Capture capacity was measured by pressure reduction in constant volume using van der Waals gas equations. The adsorption experiments were performed in the pressure range of 3–13 bar at 25, 50, and 100 C. In each cycle, first evacuation of chamber was performed using rotary and diffusion pump and CO2 gas was allowed at particular pressure and temperature. The pressure reduction was observed in the chamber due to the adsorption of CO2 in nanocomposite and the system was allowed to reach equilibrium. Each cycle of adsorption experiment was followed by degassing of CO2 at 150 C under the vacuum of 109 bar. Following to desorption, adsorption experiments were repeatedly performed to ensure

B. X-ray diffraction and XPS analysis

Figure 2(a) shows the XRD pattern for graphite oxide, HEG and Fe3O4-HEG. XRD pattern of graphite oxide shows peak at 10.6 , corresponding to the (001) diffraction peak. Oxidation of graphite leads to the increase in d-spacing. XRD pattern of HEG shows a very low intense peak around 24.4 , indicates the distorted graphite structure and hence suggests the formation of graphene sheets.24 XRD pattern of Fe3O4-HEG depicts the peaks at 2h values of 30.5 , 36 , 43.5 , 53.8 , 57.5 , 63.1 , and 74.6 , corresponding to the different planes of face centred cubic structure of Fe3O4 nanoparticles.26–28 Average size of Fe3O4 nanoparticles is found around 15 nm using Scherer’s formula. Formation of Fe3O4 phase in nanocomposite was also

FIG. 1. (a) SEM, (b) TEM, and (c) EDX images of Fe3O4-HEG, (d) Histogram of loading in different regions of Fe3O4-HEG.


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FIG. 2. (a) XRD pattern of Graphite oxide, HEG and Fe3O4-HEG (b) XPS analysis of Fe3O4-HEG.

confirmed with XPS analysis. Magnesium K alpha radiation was used for X-ray generation. Figure 2(b) shows the wide scan spectrum of the hybrid material. The photoelectron lines at binding energy of about 284, 530, 713, and 727 eV are attributed to the C 1s, O 1s, Fe 2p3/2, and Fe 2p1/2, respectively. These lines clearly suggest the Fe3O4 phase in Fe3O4-HEG nanocomposite.22 C. Surface area analysis

Figure 3 shows the N2 adsorption-desorption isotherm for nanocomposite. Surface area is calculated using Brunauer-Emmett-Teller (BET) equation. The specific surface area of the material is observed around 98.2 m2 g1 using BET equation. The inset image in Figure 3 shows the pore size distribution in Fe3O4-HEG nanocomposite. The Barrett, Joyner, and Halenda (BJH) method was used to calculate the pore size distribution. The pore volume was found to be 0.31056 cm3 g1 using BJH method with the major number of pores having average diameter around 3.8 nm, indicating the mesoporous nature of nanocomposite.

FIG. 3. N2 adsorption-desorption isotherm for Fe3O4-HEG nanocomposite, inset image shows its pore size distribution.

D. Adsorption isotherms and temperature variation

Number of moles of adsorbed CO2 was measured by calculating the number of moles of gas in the system before and after adsorption process using van der Waals gas equation.22–24 Amount of CO2 adsorbed in moles was measured by following equations: Dnadsorbed ¼ ni ðn0 þ n00 Þ;

(1)

where “ni” is the number of mole of CO2 in the initial volume “Vi” at the known initial pressure “Pi”. n0 is the number of moles in “Vi” at equilibrium pressure “Peq” and n00 is the number of moles in cell volume Vc at equilibrium pressure Peq. The gas constants a ¼ 3.67 101 J m3 mol2 and b ¼ 4.32 105 m3 mole1 were used in van der Waals gas equation for CO2. Figure 4 shows the adsorption isotherms for CO2 capture in nanocomposite. It clearly depicts the increase in CO2 capture capacity with pressure at each temperature. Increase in capture capacity with pressure may be attributed to the multilayer adsorption of CO2 and its improved interaction with nanocomposite at higher pressures. Adsorption capacities of nearly 60, 35, and 24 mmol g1 were observed at 11 bar

FIG. 4. CO2 adsorption isotherms for Fe3O4-HEG nanocomposite at different temperatures.


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TABLE I. Comparison of other solid sorbents for CO2 capture capacity.

Material Molecular Seive 13X Maxsorb AC ACs 13X Zeolite MCM Silica MWNTs Fe3O4-MWNTs Graphene Fe3O4-Graphene

Pressure (bar)/ temperature ( C)

Capture capacity (mmol g1)

Reference

12/25 35/25 12/25 12/25 12/25 11/25 11/25 11/25 11/25

4–4.5 25 10–15 3.2 5 14.3 49 11.7 60

11 13 14 15 16 22 22 23 Present work

pressure and 25, 50, and 100 C, respectively. These adsorption capacities were found higher than that of pure HEG as reported earlier.24 Adsorption capacities of 21.6, 18, and 12 mmol g1 were observed for pure HEG at 11 bar pressure and 25, 50, and 100 C temperatures, respectively.24 Although the specific surface area of Fe3O4-HEG (98.2 m2 g1) was lower than that of HEG (443 m2 g1),24 it shows higher sorption capacity compared to pure HEG. This clearly indicates that the physical adsorption of CO2 is not the only mechanism for CO2 capture in Fe3O4-HEG nanocomposite, as it depends on surface area and porosity. This suggests that an additional mechanism is involved which results in higher CO2 capture capacity of nanocomposite. This additional mechanism is related to the chemical interaction of CO2 with Fe3O4 nanoparticles in nanocomposite.29 Thus, Fe3O4-HEG nanocomposite shows the physical as well as chemical interaction with CO2 and hence physicochemical adsorption of CO2 is responsible for high CO2 capture in nanocomposite. This mechanism is further confirmed using spectroscopy studies. Capture capacity of Fe3O4-HEG nanocomposite is found higher than other solid sorbents under similar conditions as summarized in Table I. Figure 5 shows the variation in CO2 capture capacity of Fe3O4-HEG with temperature at different pressures. It

FIG. 5. Variation in CO2 captures capacity of Fe3O4-HEG nanocomposite with temperature.

clearly shows that at each pressure, CO2 capture capacity decreases with increase in temperature. This decrease in capture capacity is directly associated with larger kinetic energy of CO2 molecules at higher temperature. At higher temperature, CO2 molecules hold high rate of mobility due to their increased kinetic energy. This results in the lower interaction of CO2 molecules with porous surface of nanocomposite and Fe3O4 nanoparticles and hence in lower CO2 capture.30 It shows the CO2 capture capacity of 69.1 mmol g1 at 12 bar and 25 C. This capacity decreases to 30.6 mmol g1 at 100 C equivalent to 56% reduction in capture capacity. At the pressure of 4 bar, CO2 capture capacity is found to be 11.5 and 6.9 mmol g1 at 25 and 100 C, respectively. It is equivalent to 40% reduction in capture capacity. E. FTIR Spectroscopy Analysis

FTIR spectroscopy was performed for Fe3O4-HEG with and without CO2 capture to confirm the nature of interaction. Figure 6 shows the FTIR spectra of as prepared Fe3O4-HEG nanocomposite and CO2 captured Fe3O4-HEG nanocomposite. FTIR study of Fe3O4-HEG nanocomposite confirms the presence of ¼CH- (1578 cm1), >C¼C (1729 cm1), -CH2 (2850, 2918 cm1), and –OH (3433 cm1) functional groups over its surface.31 A broad band is observed in the range 1000–1200 cm1, which may be associated with the vibrations of >C¼O. Along with these functional groups, a peak occurs around 598 cm1, which may corresponds to the stretching vibration of Fe-O-Fe in Fe3O4.32 In case of CO2 captured Fe3O4-HEG nanocomposite, additional peaks were observed corresponding to the asymmetric stretching of CO2 molecules (2332 cm1), (O-C-O) symmetric vibrational mode of bicarbonates (1384 cm1) and (C-O) symmetric vibrational mode of carbonates (1044, 1094 cm1). Enlarged spectrum of CO2 captured Fe3O4HEG is shown as inset in Figure 6. Asymmetric stretching of

FIG. 6. FTIR spectra of Fe3O4-HEG nanocomposite with and without CO2 capture, inset image shows the enlarged peaks in the range 1200–2900 cm1 for CO2 captured nanocomposite.


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CO2 confirms the physical adsorption of CO2,33,34 while vibrational modes of bicarbonates and carbonates confirm the chemical interaction of CO2 with Fe3O4 nanoparticles.35 Formation of bicarbonates may be due to the strong interaction of CO2 with the hydroxyl groups attached to the Fe3O4 nanoparticles. Addition to these extra peaks, shifts were observed in other peaks of Fe3O4-HEG and large shift was observed stretching vibration of Fe-O-Fe (now at 578 cm1). Large shift in stretching vibration of Fe-O-Fe and presence of vibrational modes of bicarbonates and carbonates suggest the high degree of interaction of CO2 with Fe3O4 nanoparticles in nanocomposite. Thus, FTIR spectroscopy confirms the physicochemical adsorption of CO2 in Fe3O4-HEG nanocomposite. IV. CONCLUSION

High CO2 capture capacity of Fe3O4-HEG nanocomposite at high pressures and temperatures is reported. In best of our knowledge, this is the first study demonstrating the physicochemical interaction of CO2 with Fe3O4-HEG nanocomposite at elevated pressures and temperatures. The nature of the CO2 interaction with nanocomposite was confirmed using FTIR spectroscopy. The chemical interaction of CO2 with Fe3O4 nanoparticles along with physical adsorption leads to the higher CO2 capture capacity of Fe3O4-HEG nanocomposite compared to the other metal oxide and carbon materials reported earlier. Additionally, facile synthesis of nanocomposite and desorption of CO2 for repeated use of nanocomposite makes it commercially attractive. ACKNOWLEDGMENTS

The authors acknowledge the supports of IITM, Office of Alumini affairs IITM and DST, India. One of the authors (A. K. Mishra) is thankful to DST, India for providing the financial support during the work. Authors are also thankful to Department of chemistry and SAIF, IIT Madras for helping in surface area, XPS and FTIR analysis. 1

B. Hileman, Chem Eng News 84, 7 (2006). A. Hui, F. Bo, and S. Shi, Carbon 47, 2396 (2009). 3 G. P. Hao, W. C. Li, and A. H. Lu, J. Mater. Chem. 21, 6447 (2011). 4 P. D. Jadhav, S. S. Rayalu, R. B. Biniwale, and S. Devotta, Curr. Sci. 92, 724 (2007). 2

J. Appl. Phys. 116, 064306 (2014) 5

P. D. Jadhav, R. V. Chatti, R. B. Biniwale, N. K. Labshetwar, S. Devotta, and S. S. Rayalu, Energy Fuels 21, 3555 (2007). 6 X. Xu, C. Song, J. M. Anderson, B. G. Miller, and A. W. Scaroni, Micropor. Mesopor. Mater. 62, 29 (2003). 7 J. R. Karra and K. S. Walton, J. Phys. Chem. C 114, 15735 (2010). 8 B. Mu, P. M. Schoenecker, and K. S. Walton, J. Phys. Chem. C 114, 6464 (2010). 9 L. Wang and R. T. Yang, J. Phys. Chem. C 116, 1099 (2012). 10 S. Sircar, T. C. Golden, and M. B. Rao, Carbon 34, 1 (1996). 11 R. V. Siriwardane, M. Shen, E. P. Fisher, and J. Poston, Energy Fuels 15, 279 (2001). 12 T. D. Burchell, R. R. Judkins, M. R. Rogers, and A. M. Williams, Carbon 35, 1279 (1997). 13 S. Himeno, T. Komatsu, and S. Fujita, J. Chem. Eng. Data 50, 369 (2005). 14 Z. Zhang, M. Xu, H. Wang, and Z. Li, Chem. Eng. J. 160, 571 (2010). 15 S. Cavenati, C. A. Grande, and A. E. Rodrigues, J. Chem. Eng. Data 49, 1095 (2004). 16 Y. Belmabkhout, R. S. Guerrero, and A. Sayari, Chem. Eng. Sci. 64, 3721 (2009). 17 G. Pacchioni, J. M. Ricart, and F. Illas, J. Am. Chem. Soc. 116, 10152 (1994). 18 Q. Wang, J. Luo, Z. Zhong, and A. Borgna, Energy Environ. Sci. 4, 42 (2011). 19 J. D. Baniecki, M. Ishii, K. Kurihara, K. Yamanaka, T. Yano, K. Shinozaki, T. Imada, and Y. Kobayashi, J. Appl. Phys. 106, 054109 (2009). 20 M. Cinke, J. Li, C. W. Bauschlicher, Jr., A. Ricca, and M. Meyyappan, Chem. Phys. Lett. 376, 761 (2003). 21 A. Ghosh, K. S. Subrahmanyam, K. Sai Krishna, S. Datta, A. Govindaraj, S. K. Pati, and C. N. R. Rao, J. Phys. Chem. C 112, 15704 (2008). 22 A. K. Mishra and S. Ramaprabhu, Energy Environ. Sci. 4, 889 (2011). 23 A. K. Mishra and S. Ramaprabhu, RSC Adv. 2, 1746 (2012). 24 A. K. Mishra and S. Ramaprabhu, AIP Adv. 1, 032152 (2011). 25 W. Hummers, Jr. and R. E. Offeman, J. Am. Chem. Soc. 80, 1339 (1958). 26 A. K. Mishra and S. Ramaprabhu, J. Phys. Chem. C 114, 2583 (2010). 27 Z. Shu and S. Wang, J. Nanomater. 2009, 340217. 28 T. Missana, C. Maffiotte, and M. Garcıa-Gutierrez, J. Colloid Interface Sci. 261, 154 (2003). 29 S. G. Wang, X. Y. Liao, D. B. Cao, C. F. Huo, Y. W. Li, J. Wang, and H. Jiao, J. Phys. Chem. C 111, 16934 (2007). 30 X. Xu, C. Song, J. M. Anderson, B. G. Miller, and A. W. Scaroni, Energy Fuel 16, 1463 (2002). 31 U. J. Kim, C. A. Furtado, X. Liu, G. Chen, and P. C. Eklund, J. Am. Chem. Soc. 127, 15437 (2005). 32 Y. Liu, W. Jiang, Y. Wang, X. J. Zhang, D. Song, and F. S. Li, J. Magn. Magn. Mater. 321, 408 (2009). 33 W. M. Hlaing Oo, M. D. McCluskey, A. D. Lalonde, and M. G. Norton, Appl. Phys. Lett. 86, 073111 (2005). 34 W. L. Yim, O. Byl, J. T. Yates, and J. K. Johnson, J. Chem. Phys. 120, 5377 (2004). 35 J. Baltrusaitis, J. H. Jensen, and V. H. Grassian, J. Phys. Chem. B 110, 12005 (2006).
