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Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method
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Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method Minglong Zhong a, Zhibing Fu a, Rui Mi a, Xichuan Liu a, Xiaojia Li a, Lei Yuan a, Wei Huang b, Xi Yang a, Yongjian Tang a, Chaoyang Wang a,* a b
Research Center of Laser Fusion, CAEP, Mianyang 621900, China Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621900, China
article info
abstract
Article history:
A radiation method was investigated to fabricate Pt-doped carbon aerogels (CAsePt). The
Received 12 May 2018
physicochemical properties of the pristine CAs and CAsePt were systematically charac-
Received in revised form
terized by X-ray diffraction, scanning electron microscope, transmission electron micro-
22 August 2018
scopy, and nitrogen adsorption measurements. The results showed that not only a great
Accepted 25 August 2018
number of Pt nanospheres but also many Pt nanoparticles presented in the network of CAs
Available online xxx
after radiation. The influence of Pt doping on the hydrogen uptake capacity of CAs was studied. In comparison with the pristine CAs, it was remarkable that the hydrogen uptake
Keywords:
capacity of the CAsePt had been significantly enhanced, which was contributed by the
Pt-doped
hydrogen spillover of Pt.
Carbon aerogels
© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Hydrogen storage Radiation method Hydrogen spillover
Introduction The global warming due to the slather of traditional energy resources has attracted more and more attention [1,2]. So far the fossil fuels still are main energy resources with the increase of global energy demand, which brings us the increasingly severe environmental and social problems [3,4]. To solve the problems of global warming, it is important to develop renewable energy sources instead of the fossil fuels [5,6]. Hydrogen is regarded as one of the most promising alternative energy carrier for both transport and mobile applications, due to its large energy density, slow mass density and nonpolluting nature [7e9]. However, the storage of hydrogen is the major challenge for realization of hydrogen
technology in vehicular applications [10]. Since hydrogen is gaseous at ambient temperature and pressure, the compression of hydrogen consumes lots of energy and is inefficiency. Generally, the methods of hydrogen storage include liquidized hydrogen, adsorption in metal alloys, adsorption in liquid organic metal hydrides or adsorption in porous materials. Nevertheless, none of these storage methods could reach the requirements of onboard vehicular applications until now [11e15]. In order to meet the demands of vehicular applications, the US Department of Energy (DOE) has set the system capacity targets of 7.5 wt% with the condition of ambient temperature and a maximum pressure of 12 bar [16]. Hence, it is clear that the technological bottleneck of hydrogen applications is development of efficient and reliable hydrogen storage system with high capacities for mobile applications.
* Corresponding author. E-mail address: [email protected] (C. Wang). https://doi.org/10.1016/j.ijhydene.2018.08.169 0360-3199/© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
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Among various methods to hydrogen storage, adsorption based hydrogen storage on porous materials received considerable interest due to their faster adsorptiondesorption kinetics, high surface areas, excellent cyclability, light weight and chemical inertness [17]. A large number of porous materials such as zeolites, porous polymer, metal organic frameworks and porous carbons have been extensively investigated as potential hydrogen storage media [18e20]. Carbon aerogels are the most widely investigated sorbents for reversible hydrogen storage because of their high surface area, low density, high chemical and thermal stability, and they are easy to large scale preparation with low cost [21]. Nevertheless, the low binding energy of hydrogen (6 kJ mol1) requires that the cryogenic temperature (77 K) is utilized for storage of hydrogen in these materials [22]. Experimental findings showed that the maximum storage capacities of pristine carbon aerogels at room temperature was below 1 wt %, even with specific surface areas up to 2000 m2 g1 and highly developed pore structures [23e25]. For instance, Tian et al. reported the hydrogen storage value of pristine carbon aerogels with the specific surface area of 2206 m2 g1 were 4.8 wt% at 77 K and 0.5 wt% at room temperature under the same pressure (45 bar) [26]. To enhance the hydrogen uptake capacity of carbon aerogels at room temperature, one of the effective methods is to dope carbon aerogels with the noble metal, such as platinum, via the spillover effect [27e33]. Various methods have been presented to incorporate metal onto the sorbents, like the wet impregnation, atomic layer deposition (ALD), chemical vapor deposition (CVD) and plasma-assisted doping [25,34e36]. Not only the distribution and size of the metal particles but also the interaction between the supports and metal particles depend on the doping method. Thus, the doping method influences the hydrogen uptake capacity of metal-doped sorbents. In this paper, we have reported a novel method (radiation method) to fabricate Pt-doped carbon aerogels. The main advantage of radiation method is its versatility. For instance, it is well known that radiation process allows formation of nonequilibrium metal clusters such as Au cores surrounded by the Ag shell [37]. These structures are not achieved by traditional impregnation method, where the formation of cluster is obtained by high-temperature treatment, which generates equilibrium structures. The products were characterized by X-ray diffraction (XRD). The inductively couple plasma atomic emission spectrometer (ICP-AES) was used to analyze the content of Pt. The microstructure of Pt-doped carbon aerogels was determined using the transmission electron microscopy (TEM) and scanning electron microscope (SEM). Impact of Pt doping on the hydrogen uptake capacities of carbon aerogels had been studied in details.
resorcinol, formaldehyde, sodium carbonate, and deionized water were mixed in a glass vial and holding the mixture at 333 K for 6 days. The molar ratio of R/F was fixed at 1/2 and sodium carbonate was used as the catalyst. Next, crosslinked RF gels were exchanged with acetone and dried from supercritical CO2. In the end, RF aerogels were disposed to pyrolysis in a tubular oven at 1323 K under argon atmosphere to obtain the CAs.
Preparation of Pt-doped carbon aerogels The preparation procedure of Pt-doped CAs is shown in Fig. 1. A certain amount of chloroplatinic acid (1 g) was added to 20 ml of deionized water, which was stirred for 30 min in a glass vial at ambient temperature, forming a PtCl2 solution. Next, 0.2 g of CAs monoliths were immersed in 10 ml of PtCl2 solution. In order to scavenge the oxidizing radicals generated during irradiation, the proper amount of 2-Propanol was added. The mixture was deaerated by bubbling with nitrogen for 15 min to remove oxygen solvated in it and subsequently ultrasonicated for 1 h to well disperse Pt ions into CAs. Then the mixture was sealed in the reaction vial and irradiated for a total absorbed dose of 500 kGy in the 60Co g-ray radiation source at ambient temperature. The CAs after irradiation were washed with abundant ethanol and deionized water. Finally, the Pt-doped CAs were derived from drying of the resultant monoliths at 333 K in a vacuum drying oven for 5 h. The Pt-doped CAs were labeled as CAsePt in this paper. The Pt content of CAsePt is 0.21 wt%, which was measured by the ICP-AES.
Characterization The X-ray diffraction measurements were carried out on a Panalytical X΄Pert Pro X-ray diffractometry with nickel-filtered Cu Ka radiation as the X-ray source. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical states of the constituent elements. XPS spectra were acquired in XSAM 800 system and decomposed into Gaussian components by a least-square fitting method. The morphologies and energy dispersive spectroscopy (EDS) analysis of the samples were characterized by transmission electron microscope (TEM, JEM-200CM, 200 kV) and scanning electron microscope (SEM, Nova 600i). The nitrogen adsorption-desorption isotherms of the samples were obtained by using a Quantachrome Autosorb-1 instrument. The specific surface areas were calculated with the Brunauer-Emmett-Teller (BET) method, and pore size distributions with the Density Functional Theory (DFT) model [39,40]. Hydrogen sorption properties of the samples were carried out at 298 K and up to pressure of 50 bar by using a Sievert’ apparatus. The pressure-composition relationships were obtained by calculating the hydrogen storage capacity in wt%.
Experimental section Preparation of carbon aerogels
Results and discussion
Carbon aerogels (CAs) were synthesized via the established procedures as our previous work [38]. As the first step, the RF hydrogels were fabricated through a sol-gel polymerization process of resorcinol (R) and formaldehyde (F). A mount of
The powder X-ray diffraction results of the CAsePt and pristine CAs samples are presented in Fig. 2. For the pristine CAs, the two broad diffraction peaks at 23 and 43 are observed, which correspond to the (002) and (100) plane reflections of
Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
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Fig. 1 e Schematic of the radiation method for preparing CAsePt.
Fig. 2 e XRD patterns of (a) CAs and (b) CAsePt.
graphitic carbon. The broadening of (002) and (100) peaks indicates that CAs are the imperfectly crystallized solid material with some structure disorder. This is consistent with other reports. For the CAsePt, in addition to the two broad peaks, four intense inflections at 40 , 46 , 67 and 81 are clearly observed. Those peaks correspond to the (111), (200), (220), and (311) plane reflections of the cubic cell of crystalline platinum. From the analysis of XRD, it can be concluded that the metal Pt has been successfully incorporated into CAs by the radiation method. XPS measurements were carried out to investigate the chemical state of Pt in CAsePt. The XPS spectra of Pt 4f core levels for CAsePt are presented in Fig. 3. The Pt 4f core level
Fig. 3 e XPS core level spectra of the Pt 4f regions for CAse Pt.
spectrum can be divided into three pairs of doublets. The most intense peaks observed at 71.7 and 74.9.0 eV correspond to the zero valent metallic state of Pt [41], which confirms the presence of Pt in CAs after radiation. The binding energies at 73.1 and 76.1 eV can be ascribed to the existence of Pt in þ2 oxidation state. The third pair of doublets at 75.1 and 78.0 eV are attributed to the þ4 oxidation state of Pt [41,42]. The integration of peak areas reveals that most Pt species exist as metallic Pt in CAsePt, which is in agreement with the XRD analysis.
Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
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The typical SEM images of CAsePt are reported in Fig. 4. Fig. 4a shows a large amount of metal Pt particles are well distributed in the framework of CAs after radiation. This indicates the Pt particles were successfully doped in CAs by girradiation of PtCl2 solution with CAs monoliths impregnated. That process was initiated by formation of solvated electrons, and the solvated electrons were created by g-radiolysis of water in PtCl2 solution [37]. The Pt ions could be reduced by solvated electrons, thereby forming the Pt particles presented in the framework of CAs. To further investigate the microstructure of Pt particles, the micrograph of the single Pt particle in rectangular region (Fig. 4a) is presented in Fig. 4b. It is easy to note that the size of Pt particle is about 300 nm and the shape of Pt particle is spherical. Thus, the Pt particles were called as Pt nanospheres. For a further investigation of the CAsePt sample composition, the EDX analysis was carried out to determine the element distribution. The elemental mappings of C and Pt are displayed in Fig. 4c and d, respectively. A relatively uniform dispersion of the C atoms in CAsePt is clearly observed. However, Pt atoms are mainly distributed in the region of the Pt nanosphere. The SEM study suggests that the well distributed Pt nanospheres presented in the framework of CAs after radiation. In order to investigate the microstructure of the CAsePt, TEM measurements were further carried out. The TEM images of CAsePt sample are presented in Fig. 5. The presence of a spherical particle with a size of 65 nm residing in the framework of CAs is observed in Fig. 5a. The spherical particle was just one of the Pt nanospheres shown in SEM images, which had been confirmed by EDS analysis (Fig. 5d). To further
investigate the microstructure of Pt nanospheres, the HRTEM image of rectangular region in Fig. 5a are presented in Fig. 5b. As shown in Fig. 5b, the Pt nanospheres were formed by stacking of Pt nanoparticles. The circle regions in Fig. 5b represent the Pt nanoparticles composed of Pt nanospheres. This phenomenon is similar with doping Pd in CAs by using the radiation method in our previous work [43]. In the work, we have studied the microstructure and explained the forming mechanism of porous Pd microspheres. In addition to the Pt nanospheres, the Pt particles with the size of several nanometers are found in Fig. 5a. It can be seen from HRTEM image (Fig. 5c) of Fig. 5a that the shape of Pt nanoparticles is spherical or rod-like. The SEM and TEM study suggests that not only a great number of Pt nanospheres but also many Pt nanoparticles presented in the framework of CAs after radiation. The porosity analysis of the pristine CAs and CAsePt were determined by exposing the samples to nitrogen sorption at liquid nitrogen temperature (77 K). Fig. 6a reveals the nitrogen adsorption/desorption isotherms of the samples. The two samples exhibit the features of type IV isotherms with a type H2 hysteresis loop as per the IUPAC classification, typical of mesoporous materials. This indicates the porous structure of these carbons is retained after doping with Pt particles. In the low relative pressure range (less than 0.1), nitrogen adsorption capacity is very low indicating a small number of micropores in CAs. Furthermore, in the low relative pressure region that is for P/P0 below 0.3 the two isotherms are very similar. This reveals that the volume of micropores and very small mesopores was nearly unchanged. The difference between the
Fig. 4 e (a, b) SEM images and (c, d) EDX mapping distribution images of CAsePt. Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
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Fig. 5 e (a) TEM image, (b, c) HRTEM images, and (d) EDS spectrum of CAsePt.
Fig. 6 e (a) Nitrogen isotherms of CAs and CAsePt; (b) Pore size distribution of CAs and CAsePt.
pristine CAs and CAsePt is found at higher relative pressure of the nitrogen adsorption, which suggests a little decrease of larger mesopores after Pt doping. The BET analysis indicates that the specific surface area of pristine CAs decreases from 736.67 m2 g1 to 714.46 m2 g1 after Pt doping. For the CAsePt, such a decrease of the specific surface area is moderate, because the doped Pt particles possibly block some pores leading to the little decrease of the pore volume of CAs. The doping of Pt particles on the CAs was confirmed by the SEM and TEM analyses. Fig. 6b depicts a comparison of DFT calculated pore size distribution of CAs and CAsePt. The
results indicate that the mesopore volume of CAs was substantially reduced after Pt doping, and the mesopore size distribution shifted to the smaller pore size. The high pressure hydrogen adsorption measurements were done for the pristine CAs and CAsePt. Fig. 7 shows the hydrogen adsorption isotherms of pristine CAs and CAsePt at 298 K. It is observed that the hydrogen uptake capacity of the pristine CAs increases monotonously with pressure. The maximum storage capacity of 0.24 wt% has been achieved at 298 K and 50 bar pressure of hydrogen. This value is similar the hydrogen uptake measured at 298 K on other carbon
Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
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Fig. 7 e Hydrogen adsorption isotherms of CAs and CAsePt at 298 K.
materials such as carbon nanotubes [44] or ordered porous carbon template [45]. In comparison with the pristine CAs, it is remarkable that the hydrogen uptake capacity of the CAsePt has been significantly enhanced even though doping the low
content of Pt (0.21 wt%). The maximum storage capacity of CAsePt is excess three times larger than that of the pristine CAs (0.24 wt%) reaching a value of 0.78 wt% at 298 K and 50 bar. This value is higher than those in Refs. [46e49], but lower than that in Ref. [41]. For clarity, details are shown in Table 1. The enhancement of hydrogen storage should be attributed to the spillover of atomic hydrogen from Pt particles to the carbon receptor, not to the surface area difference. This is because that the CAsePt has the lower surface area than the pristine CAs, as evident from nitrogen adsorption analysis. To the hydrogen storage of the pristine CAs and CAsePt, the storage mechanism is presented in Fig. 8. It is well known that the porous carbon materials for hydrogen storage via physisorption. Furthermore, the interaction between the carbon matrix and hydrogen is van der Waals forces [19]. For the pristine CAs, hydrogen molecules are mainly stored on the surface of carbon matrix as adsorbed hydrogen or in the pores of CAs as compressed hydrogen gas. For the CAsePt, not only physical adsorption of carbon matrix but also spillover effect of the Pt particles contribute to the hydrogen storage. Firstly, hydrogen molecules are split into hydrogen atoms when hydrogen molecules meet the Pt particles. Then H atoms transfer from Pt particles to the adjacent surface of the carbon matrix via surface diffusion [41]. The high hydrogen uptake capacity of CAsePt in comparison with the pristine CAs is the
Table 1 e Hydrogen uptake capacities of different materials. Materials Gr-Pt Pt-doped OMC Pt/AC-P Pt-MSC-30 CAsePt Pt-HEG
SBET (m2 g1) 478 346 e 2810 714 298
Hydrogen uptake capacity 0.15 0.50 0.52 0.53 0.78 1.00
wt% wt% wt% wt% wt% wt%
at at at at at at
57 bar and 303 K 100 bar and 298 K 50 bar and 298 K 70 bar and 300 K 50 bar and 298 K 20 bar and 298 K
Reference [46] [47] [48] [49] present study [41]
Fig. 8 e Hydrogen storage sketch for CAs and CAsePt. Hydrogen spillover in CAsePt: Pt catalyst served as the hydrogen atom source via dissociation of hydrogen molecule, and CAs functioned as the receptor. Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
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direct evidence for hydrogen spillover of Pt particles. Here, the Pt particles act as the catalyst for H2 dissociation and CAs are the receptor. The adsorption type between Pt particles and CAs may be physisorption. There were abundant Pt seeds around the carbon matrix after g-irradiation. Then a part of Pt seeds were adsorbed onto the surface of the carbon matrix via physical interaction, which could reduce the surface energy for the nucleation and growth of Pt seeds [50e52]. Subsequently, the Pt particles onto the surface of the carbon matrix were formed by the growth of Pt seeds.
Conclusions In conclusion, we had described a new method for the preparation of Pt-doped carbon aerogels. The composites retained the characteristics of CAs with a metal Pt content of 0.21 wt%. The work was under way to demonstrate the ability of our method to synthesize Pt-doped CAs. The studies of XRD and XPS confirmed the presence of Pt in the framework of CAs. The analyses of SEM and TEM indicated that not only a great number of Pt nanospheres with the size of several hundred nanometers but also many Pt nanoparticles with the size of several nanometers presented in the framework of CAs after radiation. The formation of Pt nanospheres was similar with doping Pd in CAs by radiation method in our previous work. The reducing of the specific surface area for CAs was moderate, which was attributed to the little decrease of the pore volume after Pt doping. We had studied the hydrogen uptake capacities of the pristine CAs and CAsePt samples at ambient temperature, which supplied the direct evidence for spillover effect of Pt. The maximum storage capacities of pristine CAs and CAsePt were 0.24 wt% and 0.78 wt% at 298 K and 50 bar, respectively. By means of hydrogen spillover, the maximum storage capacity of CAs was increased with a factor of three at 298 K and 50 bar even though doping the low content of Pt.
Acknowledgement This work was financially supported by the National Natural Science Foundation of China (NSFC) under grants 51101141.
references
[1] Konni M, Dadhich AS, Mukkamala SB. Impact of surface modifications on hydrogen uptake by Fe@ f-MWCNTs and Cu@ f-MWCNTs at non-cryogenic temperatures. Int J Hydrogen Energy 2017;42:953e9. [2] Baca M, Cendrowski K, Banach P, Michalkiewicz B, Mijowska E, Kalenczuk RJ, et al. Effect of Pd loading on hydrogen storage properties of disordered mesoporous hollow carbon spheres. Int J Hydrogen Energy 2017;42:30461e9. [3] Rather SU, Hwang SW. Comparative hydrogen uptake study on titanium-MWCNTs composite prepared by two different methods. Int J Hydrogen Energy 2016;41:18114e20. [4] Wu H, Wexler D, Liu H. Effects of different palladium content loading on the hydrogen storage capacity of double-walled carbon nanotubes. Int J Hydrogen Energy 2012;37:5686e90.
7
[5] Rather SU. Hydrogen uptake of cobalt and copper oxidemultiwalled carbon nanotube composites. Int J Hydrogen Energy 2017;42:11553e9. [6] Momirlan M, Veziroglu TN. The properties of hydrogen as fuel tomorrow in sustainable energy system for a cleaner planet. Int J Hydrogen Energy 2005;30:795e802. [7] Dibandjo P, Zlotea C, Gadiou R, Ghimbeu CM, Cuevas F, Latroche M, et al. Hydrogen storage in hybrid nanostructured carbon/palladium materials: influence of particle size and surface chemistry. Int J Hydrogen Energy 2013;38:952e65. [8] Balat M. Potential importance of hydrogen as a future solution to environmental and transportation problems. Int J Hydrogen Energy 2008;33:4013e29. [9] Hosseini SE, Wahid MA. Hydrogen production from renewable and sustainable energy resources: promising green energy carrier for clean development. Renew Sustain Energy Rev 2016;57:850e66. [10] Konwar RJ, De M. Nitrogen modified templated carbons for energy application: effect of templates and nitrogen precursors. Int J Hydrogen Energy 2016;41(46):21300e9. [11] Schlapback L. Technology: hydrogen-fuelled vehicles. Nature 2009;460:809e11. [12] Jena P. Materials for hydrogen storage: past, present, and future. J Phys Chem Lett 2011;2(3):206e11. [13] Eberle U, Felderhoff M, Schu¨th F. Chemical and physical solutions for hydrogen storage. Angew Chem Int Ed 2009;48:6608e30. [14] Jain IP, Jain P, Jain A. Novel hydrogen storage materials: a review of lightweight complex hydrides. J Alloy Comp 2010;503(2):303e39. [15] Paster MD, Ahluwalia RK, Berry G, Elgowainy A, Lasher S, Mckenney K, et al. Hydrogen storage technology options for fuel cell vehicles: well-to-wheel costs, energy efficiencies, and greenhouse gas emissions. Int J Hydrogen Energy 2011;36(22):14534e51. [16] Jia Y, Sun C, Shen S, Zou J, Mao S, Yao X, et al. Combination of nanosizing and interfacial effect: future perspective for designing Mg-based nanomaterials for hydrogen storage. Renew Sustain Energy Rev 2015;44:289e303. [17] Xia Y, Yang ZX, Zhu YQ. Porous carbon-based materials for hydrogen storage: advancement and challenges. J Mater Chem A 2013;1:9365e81. [18] Pukazhselvan D, Kumar V, Singh SK. High capacity hydrogen storage: basic aspects, new developments and milestones. Nanomater Energy 2012;1:566e89. n CO. Materials for hydrogen [19] van den Berg A-W-C, Area storage: current research trends and perspectives. Chem Commun 2008;0:668e81. [20] Thomas KM. Hydrogen adsorption and storage on porous materials. Catal Today 2007;120:389e98. [21] Sakintuna B, Yu¨ru¨m Y. Templated porous carbons: a review article. Ind Eng Chem Res 2005;44(9):2893e902. [22] Panella B, Hirscher M, Roth S. Hydrogen adsorption in different carbon nanostructures. Carbon 2005;43:2209e14. [23] Tian HY, Buckley CE, Sheppard DA, Paskevicius M, Hanna N. A synthesis method for cobalt doped carbon aerogels with high surface area and their hydrogen storage properties. Int J Hydrogen Energy 2010;35:13242e6. [24] Singh S, Bhatnagar A, Dixit V, Shukla V, Shaz MA, Sinha ASK, et al. Synthesis, characterization and hydrogen storage characteristics of ambient pressure dried carbon aerogel. Int J Hydrogen Energy 2016;41:3561e70. sar C, [25] Zhao W, Fierro V, Zlotea C, Izquierdo MT, Chevalier-Ce Latroche M, et al. Activated carbons doped with Pd nanoparticles for hydrogen storage. Int J Hydrogen Energy 2012;37(6):5072e80. [26] Tian HY, Buckley CE, Paskevicius M, Sheppard DA, Wang SB, Webb CJ, et al. Nanoscale cobalt doped carbon aerogel:
Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
8
[27]
[28]
[29] [30] [31]
[32]
[33]
[34]
[35] [36]
[37]
[38]
[39]
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 8 ) 1 e8
microstructure and isosteric heat of hydrogen adsorption. Int J Hydrogen Energy 2011;36:10855e60. Biener J, Stadermann M, Suss M, Worsley MA, Biener MB, Rose KA, et al. Advanced carbon aerogels for energy applications. Energy Environ Sci 2011;4:656e67. Wang L, Lachawiec AJ, Yang RT. Nanostructured adsorbents for hydrogen storage at ambient temperature: high-pressure measurements and factors influencing hydrogen spillover. RSC Adv 2013;3:23935e52. Roland U, Braunschweig T, Roessner F. On the nature of spilt-over hydrogen. J Mol Catal A Chem 1997;127:61e84. Teichner SJ. The history and perspectives of spillover. Stud Surf Sci Catal 1993;77:27e43. Wang L, Yang FH, Yang RT. Effect of surface oxygen groups in carbons on hydrogen storage by spillover. Ind Eng Chem Res 2009;48(6):2920e6. Liu YY, Zeng JL, Zhang J, Xu F, Sun LX. Improved hydrogen storage in the modified metal-organic frameworks by hydrogen spillover effect. Int J Hydrogen Energy 2007;32(16):4005e10. Mortazavi SZ, Parvin P, Reyhani A, Malekfar R, Mirershadi S. Hydrogen storage property of laser induced Pd-nanoparticle decorated multi-walled carbon nanotubes. RSC Adv 2013;3:1397e409. Wang L, Stuckert NR, Chen H, Yang RT. Effects of Pt particle size on hydrogen storage on Pt-doped metalorganic framework IRMOF-8. J Phys Chem C 2011;115:4793e9. Liu CJ, Vissokov GP, Jang BWL. Catalyst preparation using plasma technologies. Catal Today 2002;72:173e84. Christensen ST, Feng H, Libera JL, Guo N, Miller JT, Stair PC. Supported RuPt bimetallic nanoparticle catalysts prepared by atomic layer deposition. Nano Lett 2010;10:3047e51. Hund JF, Bertino MF, Zhang G, Sotiriou-Leventis C, Leventis N, Tokuhiro AT, et al. Formation and entrapment of noble metal clusters in silica aerogel monoliths by gradiolysis. J Phys Chem B 2003;107:465e9. Zhong ML, Fu ZB, Yuan L, Zhao HB, Zhu JY, He YW, et al. A solution-phase synthesis method to prepare Pd-doped carbon aerogels for hydrogen storage. RSC Adv 2015;5:20966e71. Brunauer S, Emmet PH, Teller E. Adsorption of gases in multimolecular layers. J Am Chem Soc 1938;60:309e19.
[40] Tarazona P. Solid-fluid transition and interfaces with density functional approaches. Surf Sci 1995;331e333:989e94. [41] Divya P, Ramaprabhu S. Hydrogen storage in platinum decorated hydrogen exfoliated graphene sheets by spillover mechanism. Phys Chem Chem Phys 2014;16:26725e9. [42] Wang J, Yin G, Shao Y, Zhang S, Wang Z, Gao Y. Effect of carbon black support corrosion on the durability of Pt/C catalyst. J Power Sources 2007;171:331e9. [43] Zhong ML, Fu ZB, Huang W, Yang X, Liu M, Huang XL, et al. Fabrication of porous Pd/C microspheres in carbon aerogels by radiation method. Mater Lett 2015;139:314e7. n A, Callejas MA, Benito AM, Maser WK, Izquierdo MT, [44] Anso Rubio B, et al. Hydrogen adsorption studies on single wall carbon nanotubes. Carbon 2004;42:1243e8. [45] Campesi R, Cuevas F, Gadiou R, Leroy E, Hirscher M, VixGuterl C, et al. Hydrogen storage properties of Pd nanoparticle/carbon template composites. Carbon 2008;46:206e14. [46] Huang C, Pu N, Wang C, Huang J, Sung Y, Ger MD. Hydrogen storage in graphene decorated with Pd and Pt nano-particles using an electroless deposition technique. Separ Purif Technol 2011;82:210e5. [47] Saha D, Deng S. Hydrogen adsorption on ordered mesoporous carbons doped with Pd, Pt, Ni, and Ru. Langmuir 2009;25(21):12550e60. [48] Li Y, Yang RT, Liu CJ, Wang Z. Hydrogen storage on carbon doped with platinum nanoparticles using plasma reduction. Ind Eng Chem Res 2007;46:8277e81. [49] Stadie NP, Purewal JJ, Ahn CC, Fultz B. Measurements of hydrogen spillover in platinum doped superactivated carbon. Langmuir 2010;26:15481e5. [50] Zhao Y, Clar JG, Li L, Xu J, Yuan T, Bonzongo JCJ, et al. Selective desorption of high-purity (6,5) SWCNTs from hydrogels through surfactant modulation. Chem Commun 2016;52:2928e31. [51] O'Kelly CJ, Jung SJ, Boland JJ. Metal nanostructure synthesis via surface energy driven growth. Cryst Growth Des 2016;16:7318e24. [52] Jung SJ, Lutz T, Boese M, Holmes JD, Boland JJ. Surface energy driven agglomeration and growth of single crystal metal wires. Nano Lett 2011;11:1294e9.
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Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method Minglong Zhong a, Zhibing Fu a, Rui Mi a, Xichuan Liu a, Xiaojia Li a, Lei Yuan a, Wei Huang b, Xi Yang a, Yongjian Tang a, Chaoyang Wang a,* a b
Research Center of Laser Fusion, CAEP, Mianyang 621900, China Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621900, China
article info
abstract
Article history:
A radiation method was investigated to fabricate Pt-doped carbon aerogels (CAsePt). The
Received 12 May 2018
physicochemical properties of the pristine CAs and CAsePt were systematically charac-
Received in revised form
terized by X-ray diffraction, scanning electron microscope, transmission electron micro-
22 August 2018
scopy, and nitrogen adsorption measurements. The results showed that not only a great
Accepted 25 August 2018
number of Pt nanospheres but also many Pt nanoparticles presented in the network of CAs
Available online xxx
after radiation. The influence of Pt doping on the hydrogen uptake capacity of CAs was studied. In comparison with the pristine CAs, it was remarkable that the hydrogen uptake
Keywords:
capacity of the CAsePt had been significantly enhanced, which was contributed by the
Pt-doped
hydrogen spillover of Pt.
Carbon aerogels
© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Hydrogen storage Radiation method Hydrogen spillover
Introduction The global warming due to the slather of traditional energy resources has attracted more and more attention [1,2]. So far the fossil fuels still are main energy resources with the increase of global energy demand, which brings us the increasingly severe environmental and social problems [3,4]. To solve the problems of global warming, it is important to develop renewable energy sources instead of the fossil fuels [5,6]. Hydrogen is regarded as one of the most promising alternative energy carrier for both transport and mobile applications, due to its large energy density, slow mass density and nonpolluting nature [7e9]. However, the storage of hydrogen is the major challenge for realization of hydrogen
technology in vehicular applications [10]. Since hydrogen is gaseous at ambient temperature and pressure, the compression of hydrogen consumes lots of energy and is inefficiency. Generally, the methods of hydrogen storage include liquidized hydrogen, adsorption in metal alloys, adsorption in liquid organic metal hydrides or adsorption in porous materials. Nevertheless, none of these storage methods could reach the requirements of onboard vehicular applications until now [11e15]. In order to meet the demands of vehicular applications, the US Department of Energy (DOE) has set the system capacity targets of 7.5 wt% with the condition of ambient temperature and a maximum pressure of 12 bar [16]. Hence, it is clear that the technological bottleneck of hydrogen applications is development of efficient and reliable hydrogen storage system with high capacities for mobile applications.
* Corresponding author. E-mail address: [email protected] (C. Wang). https://doi.org/10.1016/j.ijhydene.2018.08.169 0360-3199/© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
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Among various methods to hydrogen storage, adsorption based hydrogen storage on porous materials received considerable interest due to their faster adsorptiondesorption kinetics, high surface areas, excellent cyclability, light weight and chemical inertness [17]. A large number of porous materials such as zeolites, porous polymer, metal organic frameworks and porous carbons have been extensively investigated as potential hydrogen storage media [18e20]. Carbon aerogels are the most widely investigated sorbents for reversible hydrogen storage because of their high surface area, low density, high chemical and thermal stability, and they are easy to large scale preparation with low cost [21]. Nevertheless, the low binding energy of hydrogen (6 kJ mol1) requires that the cryogenic temperature (77 K) is utilized for storage of hydrogen in these materials [22]. Experimental findings showed that the maximum storage capacities of pristine carbon aerogels at room temperature was below 1 wt %, even with specific surface areas up to 2000 m2 g1 and highly developed pore structures [23e25]. For instance, Tian et al. reported the hydrogen storage value of pristine carbon aerogels with the specific surface area of 2206 m2 g1 were 4.8 wt% at 77 K and 0.5 wt% at room temperature under the same pressure (45 bar) [26]. To enhance the hydrogen uptake capacity of carbon aerogels at room temperature, one of the effective methods is to dope carbon aerogels with the noble metal, such as platinum, via the spillover effect [27e33]. Various methods have been presented to incorporate metal onto the sorbents, like the wet impregnation, atomic layer deposition (ALD), chemical vapor deposition (CVD) and plasma-assisted doping [25,34e36]. Not only the distribution and size of the metal particles but also the interaction between the supports and metal particles depend on the doping method. Thus, the doping method influences the hydrogen uptake capacity of metal-doped sorbents. In this paper, we have reported a novel method (radiation method) to fabricate Pt-doped carbon aerogels. The main advantage of radiation method is its versatility. For instance, it is well known that radiation process allows formation of nonequilibrium metal clusters such as Au cores surrounded by the Ag shell [37]. These structures are not achieved by traditional impregnation method, where the formation of cluster is obtained by high-temperature treatment, which generates equilibrium structures. The products were characterized by X-ray diffraction (XRD). The inductively couple plasma atomic emission spectrometer (ICP-AES) was used to analyze the content of Pt. The microstructure of Pt-doped carbon aerogels was determined using the transmission electron microscopy (TEM) and scanning electron microscope (SEM). Impact of Pt doping on the hydrogen uptake capacities of carbon aerogels had been studied in details.
resorcinol, formaldehyde, sodium carbonate, and deionized water were mixed in a glass vial and holding the mixture at 333 K for 6 days. The molar ratio of R/F was fixed at 1/2 and sodium carbonate was used as the catalyst. Next, crosslinked RF gels were exchanged with acetone and dried from supercritical CO2. In the end, RF aerogels were disposed to pyrolysis in a tubular oven at 1323 K under argon atmosphere to obtain the CAs.
Preparation of Pt-doped carbon aerogels The preparation procedure of Pt-doped CAs is shown in Fig. 1. A certain amount of chloroplatinic acid (1 g) was added to 20 ml of deionized water, which was stirred for 30 min in a glass vial at ambient temperature, forming a PtCl2 solution. Next, 0.2 g of CAs monoliths were immersed in 10 ml of PtCl2 solution. In order to scavenge the oxidizing radicals generated during irradiation, the proper amount of 2-Propanol was added. The mixture was deaerated by bubbling with nitrogen for 15 min to remove oxygen solvated in it and subsequently ultrasonicated for 1 h to well disperse Pt ions into CAs. Then the mixture was sealed in the reaction vial and irradiated for a total absorbed dose of 500 kGy in the 60Co g-ray radiation source at ambient temperature. The CAs after irradiation were washed with abundant ethanol and deionized water. Finally, the Pt-doped CAs were derived from drying of the resultant monoliths at 333 K in a vacuum drying oven for 5 h. The Pt-doped CAs were labeled as CAsePt in this paper. The Pt content of CAsePt is 0.21 wt%, which was measured by the ICP-AES.
Characterization The X-ray diffraction measurements were carried out on a Panalytical X΄Pert Pro X-ray diffractometry with nickel-filtered Cu Ka radiation as the X-ray source. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical states of the constituent elements. XPS spectra were acquired in XSAM 800 system and decomposed into Gaussian components by a least-square fitting method. The morphologies and energy dispersive spectroscopy (EDS) analysis of the samples were characterized by transmission electron microscope (TEM, JEM-200CM, 200 kV) and scanning electron microscope (SEM, Nova 600i). The nitrogen adsorption-desorption isotherms of the samples were obtained by using a Quantachrome Autosorb-1 instrument. The specific surface areas were calculated with the Brunauer-Emmett-Teller (BET) method, and pore size distributions with the Density Functional Theory (DFT) model [39,40]. Hydrogen sorption properties of the samples were carried out at 298 K and up to pressure of 50 bar by using a Sievert’ apparatus. The pressure-composition relationships were obtained by calculating the hydrogen storage capacity in wt%.
Experimental section Preparation of carbon aerogels
Results and discussion
Carbon aerogels (CAs) were synthesized via the established procedures as our previous work [38]. As the first step, the RF hydrogels were fabricated through a sol-gel polymerization process of resorcinol (R) and formaldehyde (F). A mount of
The powder X-ray diffraction results of the CAsePt and pristine CAs samples are presented in Fig. 2. For the pristine CAs, the two broad diffraction peaks at 23 and 43 are observed, which correspond to the (002) and (100) plane reflections of
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Fig. 1 e Schematic of the radiation method for preparing CAsePt.
Fig. 2 e XRD patterns of (a) CAs and (b) CAsePt.
graphitic carbon. The broadening of (002) and (100) peaks indicates that CAs are the imperfectly crystallized solid material with some structure disorder. This is consistent with other reports. For the CAsePt, in addition to the two broad peaks, four intense inflections at 40 , 46 , 67 and 81 are clearly observed. Those peaks correspond to the (111), (200), (220), and (311) plane reflections of the cubic cell of crystalline platinum. From the analysis of XRD, it can be concluded that the metal Pt has been successfully incorporated into CAs by the radiation method. XPS measurements were carried out to investigate the chemical state of Pt in CAsePt. The XPS spectra of Pt 4f core levels for CAsePt are presented in Fig. 3. The Pt 4f core level
Fig. 3 e XPS core level spectra of the Pt 4f regions for CAse Pt.
spectrum can be divided into three pairs of doublets. The most intense peaks observed at 71.7 and 74.9.0 eV correspond to the zero valent metallic state of Pt [41], which confirms the presence of Pt in CAs after radiation. The binding energies at 73.1 and 76.1 eV can be ascribed to the existence of Pt in þ2 oxidation state. The third pair of doublets at 75.1 and 78.0 eV are attributed to the þ4 oxidation state of Pt [41,42]. The integration of peak areas reveals that most Pt species exist as metallic Pt in CAsePt, which is in agreement with the XRD analysis.
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The typical SEM images of CAsePt are reported in Fig. 4. Fig. 4a shows a large amount of metal Pt particles are well distributed in the framework of CAs after radiation. This indicates the Pt particles were successfully doped in CAs by girradiation of PtCl2 solution with CAs monoliths impregnated. That process was initiated by formation of solvated electrons, and the solvated electrons were created by g-radiolysis of water in PtCl2 solution [37]. The Pt ions could be reduced by solvated electrons, thereby forming the Pt particles presented in the framework of CAs. To further investigate the microstructure of Pt particles, the micrograph of the single Pt particle in rectangular region (Fig. 4a) is presented in Fig. 4b. It is easy to note that the size of Pt particle is about 300 nm and the shape of Pt particle is spherical. Thus, the Pt particles were called as Pt nanospheres. For a further investigation of the CAsePt sample composition, the EDX analysis was carried out to determine the element distribution. The elemental mappings of C and Pt are displayed in Fig. 4c and d, respectively. A relatively uniform dispersion of the C atoms in CAsePt is clearly observed. However, Pt atoms are mainly distributed in the region of the Pt nanosphere. The SEM study suggests that the well distributed Pt nanospheres presented in the framework of CAs after radiation. In order to investigate the microstructure of the CAsePt, TEM measurements were further carried out. The TEM images of CAsePt sample are presented in Fig. 5. The presence of a spherical particle with a size of 65 nm residing in the framework of CAs is observed in Fig. 5a. The spherical particle was just one of the Pt nanospheres shown in SEM images, which had been confirmed by EDS analysis (Fig. 5d). To further
investigate the microstructure of Pt nanospheres, the HRTEM image of rectangular region in Fig. 5a are presented in Fig. 5b. As shown in Fig. 5b, the Pt nanospheres were formed by stacking of Pt nanoparticles. The circle regions in Fig. 5b represent the Pt nanoparticles composed of Pt nanospheres. This phenomenon is similar with doping Pd in CAs by using the radiation method in our previous work [43]. In the work, we have studied the microstructure and explained the forming mechanism of porous Pd microspheres. In addition to the Pt nanospheres, the Pt particles with the size of several nanometers are found in Fig. 5a. It can be seen from HRTEM image (Fig. 5c) of Fig. 5a that the shape of Pt nanoparticles is spherical or rod-like. The SEM and TEM study suggests that not only a great number of Pt nanospheres but also many Pt nanoparticles presented in the framework of CAs after radiation. The porosity analysis of the pristine CAs and CAsePt were determined by exposing the samples to nitrogen sorption at liquid nitrogen temperature (77 K). Fig. 6a reveals the nitrogen adsorption/desorption isotherms of the samples. The two samples exhibit the features of type IV isotherms with a type H2 hysteresis loop as per the IUPAC classification, typical of mesoporous materials. This indicates the porous structure of these carbons is retained after doping with Pt particles. In the low relative pressure range (less than 0.1), nitrogen adsorption capacity is very low indicating a small number of micropores in CAs. Furthermore, in the low relative pressure region that is for P/P0 below 0.3 the two isotherms are very similar. This reveals that the volume of micropores and very small mesopores was nearly unchanged. The difference between the
Fig. 4 e (a, b) SEM images and (c, d) EDX mapping distribution images of CAsePt. Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
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Fig. 5 e (a) TEM image, (b, c) HRTEM images, and (d) EDS spectrum of CAsePt.
Fig. 6 e (a) Nitrogen isotherms of CAs and CAsePt; (b) Pore size distribution of CAs and CAsePt.
pristine CAs and CAsePt is found at higher relative pressure of the nitrogen adsorption, which suggests a little decrease of larger mesopores after Pt doping. The BET analysis indicates that the specific surface area of pristine CAs decreases from 736.67 m2 g1 to 714.46 m2 g1 after Pt doping. For the CAsePt, such a decrease of the specific surface area is moderate, because the doped Pt particles possibly block some pores leading to the little decrease of the pore volume of CAs. The doping of Pt particles on the CAs was confirmed by the SEM and TEM analyses. Fig. 6b depicts a comparison of DFT calculated pore size distribution of CAs and CAsePt. The
results indicate that the mesopore volume of CAs was substantially reduced after Pt doping, and the mesopore size distribution shifted to the smaller pore size. The high pressure hydrogen adsorption measurements were done for the pristine CAs and CAsePt. Fig. 7 shows the hydrogen adsorption isotherms of pristine CAs and CAsePt at 298 K. It is observed that the hydrogen uptake capacity of the pristine CAs increases monotonously with pressure. The maximum storage capacity of 0.24 wt% has been achieved at 298 K and 50 bar pressure of hydrogen. This value is similar the hydrogen uptake measured at 298 K on other carbon
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Fig. 7 e Hydrogen adsorption isotherms of CAs and CAsePt at 298 K.
materials such as carbon nanotubes [44] or ordered porous carbon template [45]. In comparison with the pristine CAs, it is remarkable that the hydrogen uptake capacity of the CAsePt has been significantly enhanced even though doping the low
content of Pt (0.21 wt%). The maximum storage capacity of CAsePt is excess three times larger than that of the pristine CAs (0.24 wt%) reaching a value of 0.78 wt% at 298 K and 50 bar. This value is higher than those in Refs. [46e49], but lower than that in Ref. [41]. For clarity, details are shown in Table 1. The enhancement of hydrogen storage should be attributed to the spillover of atomic hydrogen from Pt particles to the carbon receptor, not to the surface area difference. This is because that the CAsePt has the lower surface area than the pristine CAs, as evident from nitrogen adsorption analysis. To the hydrogen storage of the pristine CAs and CAsePt, the storage mechanism is presented in Fig. 8. It is well known that the porous carbon materials for hydrogen storage via physisorption. Furthermore, the interaction between the carbon matrix and hydrogen is van der Waals forces [19]. For the pristine CAs, hydrogen molecules are mainly stored on the surface of carbon matrix as adsorbed hydrogen or in the pores of CAs as compressed hydrogen gas. For the CAsePt, not only physical adsorption of carbon matrix but also spillover effect of the Pt particles contribute to the hydrogen storage. Firstly, hydrogen molecules are split into hydrogen atoms when hydrogen molecules meet the Pt particles. Then H atoms transfer from Pt particles to the adjacent surface of the carbon matrix via surface diffusion [41]. The high hydrogen uptake capacity of CAsePt in comparison with the pristine CAs is the
Table 1 e Hydrogen uptake capacities of different materials. Materials Gr-Pt Pt-doped OMC Pt/AC-P Pt-MSC-30 CAsePt Pt-HEG
SBET (m2 g1) 478 346 e 2810 714 298
Hydrogen uptake capacity 0.15 0.50 0.52 0.53 0.78 1.00
wt% wt% wt% wt% wt% wt%
at at at at at at
57 bar and 303 K 100 bar and 298 K 50 bar and 298 K 70 bar and 300 K 50 bar and 298 K 20 bar and 298 K
Reference [46] [47] [48] [49] present study [41]
Fig. 8 e Hydrogen storage sketch for CAs and CAsePt. Hydrogen spillover in CAsePt: Pt catalyst served as the hydrogen atom source via dissociation of hydrogen molecule, and CAs functioned as the receptor. Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
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direct evidence for hydrogen spillover of Pt particles. Here, the Pt particles act as the catalyst for H2 dissociation and CAs are the receptor. The adsorption type between Pt particles and CAs may be physisorption. There were abundant Pt seeds around the carbon matrix after g-irradiation. Then a part of Pt seeds were adsorbed onto the surface of the carbon matrix via physical interaction, which could reduce the surface energy for the nucleation and growth of Pt seeds [50e52]. Subsequently, the Pt particles onto the surface of the carbon matrix were formed by the growth of Pt seeds.
Conclusions In conclusion, we had described a new method for the preparation of Pt-doped carbon aerogels. The composites retained the characteristics of CAs with a metal Pt content of 0.21 wt%. The work was under way to demonstrate the ability of our method to synthesize Pt-doped CAs. The studies of XRD and XPS confirmed the presence of Pt in the framework of CAs. The analyses of SEM and TEM indicated that not only a great number of Pt nanospheres with the size of several hundred nanometers but also many Pt nanoparticles with the size of several nanometers presented in the framework of CAs after radiation. The formation of Pt nanospheres was similar with doping Pd in CAs by radiation method in our previous work. The reducing of the specific surface area for CAs was moderate, which was attributed to the little decrease of the pore volume after Pt doping. We had studied the hydrogen uptake capacities of the pristine CAs and CAsePt samples at ambient temperature, which supplied the direct evidence for spillover effect of Pt. The maximum storage capacities of pristine CAs and CAsePt were 0.24 wt% and 0.78 wt% at 298 K and 50 bar, respectively. By means of hydrogen spillover, the maximum storage capacity of CAs was increased with a factor of three at 298 K and 50 bar even though doping the low content of Pt.
Acknowledgement This work was financially supported by the National Natural Science Foundation of China (NSFC) under grants 51101141.
references
[1] Konni M, Dadhich AS, Mukkamala SB. Impact of surface modifications on hydrogen uptake by Fe@ f-MWCNTs and Cu@ f-MWCNTs at non-cryogenic temperatures. Int J Hydrogen Energy 2017;42:953e9. [2] Baca M, Cendrowski K, Banach P, Michalkiewicz B, Mijowska E, Kalenczuk RJ, et al. Effect of Pd loading on hydrogen storage properties of disordered mesoporous hollow carbon spheres. Int J Hydrogen Energy 2017;42:30461e9. [3] Rather SU, Hwang SW. Comparative hydrogen uptake study on titanium-MWCNTs composite prepared by two different methods. Int J Hydrogen Energy 2016;41:18114e20. [4] Wu H, Wexler D, Liu H. Effects of different palladium content loading on the hydrogen storage capacity of double-walled carbon nanotubes. Int J Hydrogen Energy 2012;37:5686e90.
7
[5] Rather SU. Hydrogen uptake of cobalt and copper oxidemultiwalled carbon nanotube composites. Int J Hydrogen Energy 2017;42:11553e9. [6] Momirlan M, Veziroglu TN. The properties of hydrogen as fuel tomorrow in sustainable energy system for a cleaner planet. Int J Hydrogen Energy 2005;30:795e802. [7] Dibandjo P, Zlotea C, Gadiou R, Ghimbeu CM, Cuevas F, Latroche M, et al. Hydrogen storage in hybrid nanostructured carbon/palladium materials: influence of particle size and surface chemistry. Int J Hydrogen Energy 2013;38:952e65. [8] Balat M. Potential importance of hydrogen as a future solution to environmental and transportation problems. Int J Hydrogen Energy 2008;33:4013e29. [9] Hosseini SE, Wahid MA. Hydrogen production from renewable and sustainable energy resources: promising green energy carrier for clean development. Renew Sustain Energy Rev 2016;57:850e66. [10] Konwar RJ, De M. Nitrogen modified templated carbons for energy application: effect of templates and nitrogen precursors. Int J Hydrogen Energy 2016;41(46):21300e9. [11] Schlapback L. Technology: hydrogen-fuelled vehicles. Nature 2009;460:809e11. [12] Jena P. Materials for hydrogen storage: past, present, and future. J Phys Chem Lett 2011;2(3):206e11. [13] Eberle U, Felderhoff M, Schu¨th F. Chemical and physical solutions for hydrogen storage. Angew Chem Int Ed 2009;48:6608e30. [14] Jain IP, Jain P, Jain A. Novel hydrogen storage materials: a review of lightweight complex hydrides. J Alloy Comp 2010;503(2):303e39. [15] Paster MD, Ahluwalia RK, Berry G, Elgowainy A, Lasher S, Mckenney K, et al. Hydrogen storage technology options for fuel cell vehicles: well-to-wheel costs, energy efficiencies, and greenhouse gas emissions. Int J Hydrogen Energy 2011;36(22):14534e51. [16] Jia Y, Sun C, Shen S, Zou J, Mao S, Yao X, et al. Combination of nanosizing and interfacial effect: future perspective for designing Mg-based nanomaterials for hydrogen storage. Renew Sustain Energy Rev 2015;44:289e303. [17] Xia Y, Yang ZX, Zhu YQ. Porous carbon-based materials for hydrogen storage: advancement and challenges. J Mater Chem A 2013;1:9365e81. [18] Pukazhselvan D, Kumar V, Singh SK. High capacity hydrogen storage: basic aspects, new developments and milestones. Nanomater Energy 2012;1:566e89. n CO. Materials for hydrogen [19] van den Berg A-W-C, Area storage: current research trends and perspectives. Chem Commun 2008;0:668e81. [20] Thomas KM. Hydrogen adsorption and storage on porous materials. Catal Today 2007;120:389e98. [21] Sakintuna B, Yu¨ru¨m Y. Templated porous carbons: a review article. Ind Eng Chem Res 2005;44(9):2893e902. [22] Panella B, Hirscher M, Roth S. Hydrogen adsorption in different carbon nanostructures. Carbon 2005;43:2209e14. [23] Tian HY, Buckley CE, Sheppard DA, Paskevicius M, Hanna N. A synthesis method for cobalt doped carbon aerogels with high surface area and their hydrogen storage properties. Int J Hydrogen Energy 2010;35:13242e6. [24] Singh S, Bhatnagar A, Dixit V, Shukla V, Shaz MA, Sinha ASK, et al. Synthesis, characterization and hydrogen storage characteristics of ambient pressure dried carbon aerogel. Int J Hydrogen Energy 2016;41:3561e70. sar C, [25] Zhao W, Fierro V, Zlotea C, Izquierdo MT, Chevalier-Ce Latroche M, et al. Activated carbons doped with Pd nanoparticles for hydrogen storage. Int J Hydrogen Energy 2012;37(6):5072e80. [26] Tian HY, Buckley CE, Paskevicius M, Sheppard DA, Wang SB, Webb CJ, et al. Nanoscale cobalt doped carbon aerogel:
Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169
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[27]
[28]
[29] [30] [31]
[32]
[33]
[34]
[35] [36]
[37]
[38]
[39]
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microstructure and isosteric heat of hydrogen adsorption. Int J Hydrogen Energy 2011;36:10855e60. Biener J, Stadermann M, Suss M, Worsley MA, Biener MB, Rose KA, et al. Advanced carbon aerogels for energy applications. Energy Environ Sci 2011;4:656e67. Wang L, Lachawiec AJ, Yang RT. Nanostructured adsorbents for hydrogen storage at ambient temperature: high-pressure measurements and factors influencing hydrogen spillover. RSC Adv 2013;3:23935e52. Roland U, Braunschweig T, Roessner F. On the nature of spilt-over hydrogen. J Mol Catal A Chem 1997;127:61e84. Teichner SJ. The history and perspectives of spillover. Stud Surf Sci Catal 1993;77:27e43. Wang L, Yang FH, Yang RT. Effect of surface oxygen groups in carbons on hydrogen storage by spillover. Ind Eng Chem Res 2009;48(6):2920e6. Liu YY, Zeng JL, Zhang J, Xu F, Sun LX. Improved hydrogen storage in the modified metal-organic frameworks by hydrogen spillover effect. Int J Hydrogen Energy 2007;32(16):4005e10. Mortazavi SZ, Parvin P, Reyhani A, Malekfar R, Mirershadi S. Hydrogen storage property of laser induced Pd-nanoparticle decorated multi-walled carbon nanotubes. RSC Adv 2013;3:1397e409. Wang L, Stuckert NR, Chen H, Yang RT. Effects of Pt particle size on hydrogen storage on Pt-doped metalorganic framework IRMOF-8. J Phys Chem C 2011;115:4793e9. Liu CJ, Vissokov GP, Jang BWL. Catalyst preparation using plasma technologies. Catal Today 2002;72:173e84. Christensen ST, Feng H, Libera JL, Guo N, Miller JT, Stair PC. Supported RuPt bimetallic nanoparticle catalysts prepared by atomic layer deposition. Nano Lett 2010;10:3047e51. Hund JF, Bertino MF, Zhang G, Sotiriou-Leventis C, Leventis N, Tokuhiro AT, et al. Formation and entrapment of noble metal clusters in silica aerogel monoliths by gradiolysis. J Phys Chem B 2003;107:465e9. Zhong ML, Fu ZB, Yuan L, Zhao HB, Zhu JY, He YW, et al. A solution-phase synthesis method to prepare Pd-doped carbon aerogels for hydrogen storage. RSC Adv 2015;5:20966e71. Brunauer S, Emmet PH, Teller E. Adsorption of gases in multimolecular layers. J Am Chem Soc 1938;60:309e19.
[40] Tarazona P. Solid-fluid transition and interfaces with density functional approaches. Surf Sci 1995;331e333:989e94. [41] Divya P, Ramaprabhu S. Hydrogen storage in platinum decorated hydrogen exfoliated graphene sheets by spillover mechanism. Phys Chem Chem Phys 2014;16:26725e9. [42] Wang J, Yin G, Shao Y, Zhang S, Wang Z, Gao Y. Effect of carbon black support corrosion on the durability of Pt/C catalyst. J Power Sources 2007;171:331e9. [43] Zhong ML, Fu ZB, Huang W, Yang X, Liu M, Huang XL, et al. Fabrication of porous Pd/C microspheres in carbon aerogels by radiation method. Mater Lett 2015;139:314e7. n A, Callejas MA, Benito AM, Maser WK, Izquierdo MT, [44] Anso Rubio B, et al. Hydrogen adsorption studies on single wall carbon nanotubes. Carbon 2004;42:1243e8. [45] Campesi R, Cuevas F, Gadiou R, Leroy E, Hirscher M, VixGuterl C, et al. Hydrogen storage properties of Pd nanoparticle/carbon template composites. Carbon 2008;46:206e14. [46] Huang C, Pu N, Wang C, Huang J, Sung Y, Ger MD. Hydrogen storage in graphene decorated with Pd and Pt nano-particles using an electroless deposition technique. Separ Purif Technol 2011;82:210e5. [47] Saha D, Deng S. Hydrogen adsorption on ordered mesoporous carbons doped with Pd, Pt, Ni, and Ru. Langmuir 2009;25(21):12550e60. [48] Li Y, Yang RT, Liu CJ, Wang Z. Hydrogen storage on carbon doped with platinum nanoparticles using plasma reduction. Ind Eng Chem Res 2007;46:8277e81. [49] Stadie NP, Purewal JJ, Ahn CC, Fultz B. Measurements of hydrogen spillover in platinum doped superactivated carbon. Langmuir 2010;26:15481e5. [50] Zhao Y, Clar JG, Li L, Xu J, Yuan T, Bonzongo JCJ, et al. Selective desorption of high-purity (6,5) SWCNTs from hydrogels through surfactant modulation. Chem Commun 2016;52:2928e31. [51] O'Kelly CJ, Jung SJ, Boland JJ. Metal nanostructure synthesis via surface energy driven growth. Cryst Growth Des 2016;16:7318e24. [52] Jung SJ, Lutz T, Boese M, Holmes JD, Boland JJ. Surface energy driven agglomeration and growth of single crystal metal wires. Nano Lett 2011;11:1294e9.
Please cite this article in press as: Zhong M, et al., Fabrication of Pt-doped carbon aerogels for hydrogen storage by radiation method, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/j.ijhydene.2018.08.169