Synthesis, Nickel Decoration, and Hydrogen Adsorption of Silica

Sep 28, 2015 - In this work mesoporous carbon material with ultrahigh surface area is prepared with hexagonally packed mesoporous silica (HMS) as ...
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Synthesis, Nickel Decoration, and Hydrogen Adsorption of SilicaTemplated Mesoporous Carbon Material with High Surface Area Jinsong Shi,†,‡ Weibin Li,*,†,‡ and Dan Li† †

Graduate School at Shenzhen, Tsinghua University, University Town, Nanshan District, Shenzhen 518055, China Department of Chemistry, Tsinghua University, Haidian District, Beijing 100084, China

‡

S Supporting Information *

ABSTRACT: Porous carbons are important adsorbents for hydrogen. In this work mesoporous carbon material with ultrahigh surface area is prepared with hexagonally packed mesoporous silica (HMS) as template. After a systematic optimization of different synthesis parameters, carbon material with a specific surface area of 2644 m2/g is obtained with resol as carbon precursors, the highest value reported so far for silica-templated mesoporous carbons. The material can be loaded with nickel nanoparticles through addition of nickel chloride hexahydrate into the resol solution. Hydrogen uptake of the nickel-decorated carbon at room temperature and 20 bar reaches 2.66 mmol/g, 78% higher than that of the pristine carbon. Due to the sharp decrease of the specific surface area and pore volume after nickel decoration, the improvement is attributed to effects of nickel nanoparticles.

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INTRODUCTION Hydrogen is a potential candidate for future energy due to its high energy density and environmental benignity. Hydrogen storage by porous materials employing physisorption has merits of good reversibility and fast kinetics.1,2 Porous materials such as metal−organic frameworks (MOFs),3 porous organic polymers,4 and porous carbons5 have been widely studied. Although the adsorption capacity at cryogenic temperature is encouraging, it decreases drastically at room temperature due to the weak adsorption energy.6−9 The spillover approach is reported to be a promising technique for the improvement of storage properties at room temperature.3,6,8 In a typical adsorption process, the hydrogen molecule is first dissociated on a metal surface, and then atomic hydrogen is transported onto the surface of adsorbent and adsorbed. Different metals including Pt,10 Pd,11 Ru,12 and Ni13 can trigger the spillover process. For nickel-loaded porous carbons, Lin et al. studied the effects of nickel content and particle size on hydrogen adsorption properties of nickeldecorated carbon nanotubes; an enhancement factor of 3 was achieved by 10.1 wt % Ni with a particle size of 2.3 nm at room temperature.14 Giraudet et al. prepared nickel-loaded ordered mesoporous CMK-3 with the impregnation method, although the nickel particle size was small (5−10 nm); the adsorption amount increase at 298 K was a relatively lower 67%.15 However, for the preparation of metal-loaded adsorbent, in most cases metal particles are incorporated after the synthesis of the adsorbent through methods like mechanical mixing8 or the incipient wetness impregnation method.12,13,16 A simultaneous synthesis process will undoubtedly increase the efficiency. Besides characteristics of high surface area and large pore volume, porous carbon also has outstanding thermal and chemical stability, triggering interest in different areas. For © XXXX American Chemical Society

applications such as hydrogen storage, a high specific surface area is indispensable to superior performance, and micropores, especially those smaller than 1 nm, have decisive impacts on the hydrogen adsorption amount.5,17 However, microporous carbons have their own disadvantages including slow mass transport due to space confinement of small pores,18−22 while mesoporous structure can greatly alleviate this limitation. In this context, mesoporous carbons with high specific surface area could be a significant supplement to microporous carbons for hydrogen adsorption research. The hard template strategy is widely applied for the preparation of mesoporous carbons, in which rigid porous materials such as silica are usually used as the sacrificial hard template. Although the structure of carbon materials could be tuned by the choice of different templates, in only very limited cases the specific surface area could be higher than 2000 m2/g. For instance, the surface area of CMK carbon is generally lower than or close to 2000 m2/g.23−25 Sevilla et al. prepared porous carbons with HMS as template and furfuryl alcohol as carbon precursor, with the highest specific area of 2340 m2/g.26 Zhao’s group developed an evaporation-induced triconstituent coassembly approach, where tetraethyl orthosilicate was mixed with resol and triblock copolymer Pluronic F127.27−29 The generated silica network inhibited framework shrinkage during calcination, acting as an in-situ-formed hard template. The removal of F127 and silica yielded carbon with a specific surface area as high as 2470 m2/g.27 In this work we present the synthesis of highly porous carbon materials with a BET surface area of 2644 m2/g via the hard template method, with hexagonally packed mesoporous silica (HMS) as the sacrificial hard template and resol as the carbon Received: June 24, 2015 Revised: September 27, 2015

A

DOI: 10.1021/acs.jpcc.5b06049 J. Phys. Chem. C XXXX, XXX, XXX−XXX

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The Journal of Physical Chemistry C source. The carbons were successfully loaded with nickel nanoparticles during the carbonization process. Hydrogen adsorption isotherms of these carbon materials were investigated with the static volumetric method; the results showed that the corresponding adsorption amount could be significantly enhanced by nickel nanoparticles at room temperature.

Table 1. Comparative Results for the Hydrogen Adsorption Amount of Different Adsorbents

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EXPERIMENTAL SECTION Materials. Dodecylamine (DDA, 98.0 wt %) was supplied by Aladdin Industrial Corp. Other materials including phenol, formalin solution (37 wt %), tetraethyl orthosilicate (TEOS), NiCl2·6H2O, sucrose, and glucose were purchased from Sinopharm Chemical Reagent Co., Ltd. All chemicals were used directly. Synthesis of Hexagonally Packed Mesoporous Silica (HMS). HMS was synthesized with TEOS and DDA.30 A 5.0 g amount of DDA was dissolved in 53 mL of deionized water and 53 mL of ethanol; 20.8 g of TEOS was then added to this solution with vigorous stirring. The reactant mixture was kept stirring for 18 h. All these procedures were carried out at room temperature. The solid products were filtered and washed with water and then dried at 100 °C in open air. The DDA template was removed by calcination in air at 630 °C for 4 h with a heating rate of 2 °C/min. Synthesis of Mesoporous Carbons and Nickel-Decorated Carbons. The porous carbon material was prepared with an impregnation method. In a typical synthesis, resol precursors were first prepared according to the literature method.27 Then 1.0 g of HMS was added to 7.18 g of 20 wt % resol ethanolic solution. The mixture was kept stirring at room temperature for the evaporation of ethanol until a uniform translucent product was obtained (Figure S1a), which was then treated at 100 °C for 24 h in open air. The obtained brown solid was crushed into powders and subjected to carbonization treatment in a tube furnace in nitrogen with a flow rate of 50 mL/min. The sample was calcined at 700 °C for 2 h with a heating rate of 3 °C/min. After being cooled to room temperature, the black product was treated with 10 wt % HF solution to remove the HMS template. The hydrofluoric acid used in this work is very corrosive; please handle with caution. The carbon material was washed with deionized water repeatedly and then dried at 100 °C. The yielded mesoporous carbon material was denoted as MC. Samples with different synthesis parameters (carbon precursor/template ratio, carbonization temperature/time, heating rate) were prepared in a similar manner (Table S1); the conditions were the same as MC unless specified in Table S1. Preparation of nickel-decorated carbon was similar to that of MC. In a typical synthesis, 0.20 g of NiCl2·6H2O was dissolved in 7.18 g of 20 wt % resol ethanolic solution, followed by the addition of 1.0 g of HMS. The mixture was kept stirring at room temperature until it turned into a uniform light green translucent product (Figure S1b). After being dried at 100 °C for 24 h, the dark brown solid was treated at 700 °C for 2 h in nitrogen with a flow rate of 50 mL/min. The heating rate was 3 °C/min. The furnace temperature then decreased slowly to room temperature. HMS template was removed by 2 M NaOH aqueous solution at 80 °C for 24 h. The nickel-decorated carbon material was washed with deionized water repeatedly and then dried at room temperature. The products were denoted as NDC-1, NDC-2, NDC-3, and NCD-4, corresponding to different addition amounts of NiCl2·6H2O and final nickel content (Table 1).

sample

NiCl2· 6H2O (g)

Ni content (wt %)

BET surface area (m2/g)

crystallite size calculated by Scherrer formula (nm)

hydrogen adsorbed at 2 MPa (mmol/g)

MC NDC-1 NDC-2 NDC-3 NDC-4

0 0.050 0.117 0.200 0.294

0 1.6 2.6 4.3 5.8

2644 1799 1675 1326 1109

29.3 34.8 34.5 35.7

1.487 0.948 1.760 2.660 2.060

Characterization and Hydrogen Adsorption Test. Powder XRD analysis was performed using a Rigaku D/ MAX-2500/PC. The morphology of the samples was examined by a scanning electron microscope (SEM, Hitachi S-4800). The nickel content in the carbon−nickel composite was determined by inductively coupled plasma-atomic emission spectrometry (ICP, Agilent 7500ce). Transmission electron microscopy (TEM) was conducted on FEI Tecnai F30. The nitrogen adsorption−desorption isotherms at 77 K were measured on a Micromeritics ASAP 2020 analyzer. Samples were degassed at 170 °C for 3 h before testing. The specific surface area was obtained with the Brunauer−Emmett−Teller (BET) method from adsorption branch in a relative pressure range of P/P0 < 0.3; the pore size distribution curve was calculated with the density functional theory (DFT) method;31 the adsorption amount at P/P0 = ca. 0.99 was employed to calculate the total pore volume (Vt); the micropore volume (Vmicro) was obtained with the Dubinin−Radushkevich (DR) equation, while the mesopore volume (Vmeso) was calculated by subtracting Vmicro from Vt. Hydrogen adsorption isotherms of different samples were measured at room temperature (295 K) and at pressures up to 20 bar with the static volumetric method on a Sieverttype equipment. The Soave−Redlich−Kwong (SRK) equation was employed for calculation of the compressibility factor z.32 All samples were treated at 170 °C under vacuum for at least 3 h to remove adsorbed water and other contaminants before hydrogen adsorption measurements.

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RESULTS AND DISCUSSION For the preparation of MC, HMS is impregnated with aqueous or ethanolic solution of carbon precursors and then removed after the carbonization process. The choice of carbon precursors is of primary importance. Glucose and sucrose are investigated as the carbon sources, since these compounds are the first choice of carbon precursors for the preparation of mesoporous carbons like CMK-3.23,25 However, the highest specific surface area achieved is only 1100 m2/g (Tables S2 and S3). Resol is a low molecular weight phenolic resin produced by reacting phenol and formaldehyde; it can bond with the PEO groups of soft templates like F127 and is frequently used as carbon precursors for the preparation of FDU materials.20,27 The direct carbonization of resol produces very dense carbon material with a surface area lower than 1 m2/g; porous structure could not be obtained under this situation. However, with the assistance of HMS, highly porous carbon materials are attainable. Impacts of different synthesis parameters including the carbon precursor/template ratio, carbonization temperature/time, and heating rate on the specific surface area are studied (Table S1). A suitable carbon precursor/template ratio should guarantee the complete filling of HMS pore channels and minimum carbonization reactions outside the pore B

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final nickel content in NDC could be tuned by changing the addition amount of nickel chloride. The specific surface area decreases with the increase of nickel content; also, a slight increase of nickel crystallite size occurs when nickel content reaches 2.6 wt %, as shown in Table 1. The nitrogen adsorption−desorption isotherms and pore size distribution curves of samples are given in Figure 2a and 2b,

channels at the same time; the resol/HMS ratio is thus fixed at 1.44 g/g in this work. Suitable heat treatment conditions allow complete carbonization of carbon precursors without destroying the porous structure. Results in Table S1 indicate that the excessive increase of the treatment time and temperature yield carbons with a lower surface area. After a systematic optimization process, resol is carbonized at 700 °C for 2 h with a heating rate of 3 °C/min, and mesoporous carbon with specific surface area higher than 2500 m2/g is obtained. For the preparation of NDC, NiCl2·6H2O is dissolved in resol solution; nickel species are then reduced to metallic nickel during the high-temperature carbonization process. The smallangle XRD (SAXRD) patterns of HMS, MC, and NDC-3 are displayed in Figure S2. HMS shows a single broad peak between 1° and 3.5°, typical of disordered wormhole-like structure.33,34 MC and NDC-3 inherit this feature, but the peak density weakens for NDC-3. The wide-angle XRD patterns of different NDC samples in Figure 1 show two peaks at 44.5° and

Figure 1. XRD patterns of HMS template, MC, and NDC materials.

51.9°, corresponding to the (111) and (200) reflections of metallic nickel, respectively, confirming the reduction of nickel species during the carbonization process. However, a very weak peak at 43.3° could also be detected for NDC-1, suggesting the existence of a trace amount of nickel oxide in the final product. Although nitrogen of high purity (>99.999%) is used in this work, the oxidization of nickel nanoparticles by impurity gases like oxygen during the carbonization process is still possible. In order to investigate this hypothesis, copper powder was treated directly with the same heating protocol as NDC. It was observed that the surface of the copper material close to the inlet of nitrogen turned into a dark black color, which should be caused by the oxidization reactions of impurities in nitrogen. The calculated average crystallite size of NDC-3 with the Scherrer formula is 34.5 nm. This value is higher than that of nickel nanoparticles prepared with the traditional wet impregnation method in some reports.15,35,36 In order to gain insights into this result, in a control experiment nickel chloride and resol solution were mixed together without the addition of HMS. After treatment at 100 °C for 24 h, a clear phase separation phenomenon occurred, with green nickel salt materials at the bottom and brown resol materials at the top. For NDC materials, although HMS pore walls can restrain the phase separation effectively, such effects could not be completely eliminated. The agglomeration of nickel chloride will result in the formation of lager nickel nanoparticles. The

Figure 2. (a) Nitrogen adsorption−desorption isotherms at 77 K, and (b) pore size distributions calculated by density functional theory (DFT).

respectively. The isotherms in Figure 2a have similar shapes, demonstrating mixed features of Type I and Type IV. The steep uptake at the low-pressure region indicates the existence of micropores. The nitrogen adsorption amount of HMS at this region is lower than that of MC and NDC-3; an increase of micropore volume is expected for the latter two. The knees of the isotherms in the relative pressure range of 0.02−0.4 should also be formed by small mesopores or large micropores.17,37 The shape of the hysteresis loops is categorized as type H3, characteristic of loose assemblages of platelike particles with slitlike pores.38 The DFT pore size distribution curve of HMS in Figure 2b shows two peaks at 1.4 and 2.7 nm, confirming the existence of both micropores and small mesopores, with Vmicro and Vmeso of 0.34 and 0.44 cm3/g, respectively. MC also displays two peaks centered at 1.3 and 2.7 nm, with higher Vmicro and Vmeso of 0.58 and 0.74 cm3/g, respectively. It is worth emphasizing that the BET surface area of MC is 2644 m2/g, much higher than that of HMS (1172 m2/g). To the best of our C

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The Journal of Physical Chemistry C knowledge, this value is even higher than some of the best results reported so far for carbon materials obtained directly from a silica template (Table S4).23,26−29 For NDC-3 the peak of mesopores at approximately 2.2 nm in Figure 2b weakens significantly, suggesting the loss of mesoporosity. The Vmicro and Vmeso of NDC-3 are 0.41 and 0.32 cm3/g, respectively, while the BET surface area also decreases to 1326 m2/g. The loss of porosity and specific surface area suggests that nickel nanoparticles may cause a serious pore-blocking phenomenon in NDC materials. SEM images are displayed in Figure 3. HMS in Figure 3a consists of platelike particles forming large aggregates. MC and

Figure 5. Hydrogen adsorption isotherms of MC and NDC samples at room temperature (295 K). Figure 3. SEM images of (a) HMS, (b) MC, and (c) NDC-3.

adsorbents.8,39 After nickel loading, the hydrogen adsorption amount increases except NDC-1, NDC with the lowest nickel amount. As shown in Table 1, the adsorption amount increases with nickel content first and then decreases. NDC-3 gives the best result of 2.66 mmol/g (0.53 wt %), corresponding to a 78% increase when compared with MC. Nickel decoration changes the porosity of NDC materials and decreases the specific surface area, micropore volume, and mesopore volume at the same time, each of which has negative effects on hydrogen adsorption capacity. Considering these impacts, the improved hydrogen adsorption amount should be attributed to spillover effects by nickel particles. Although precious metals are the most intensively studied catalysts for the hydrogen spillover process, transition metals such as nickel14,15,40 and cobalt41 can also act as effective catalysts. A very obvious surface area drop is associated with nickel decoration, which imposes a negative influence on hydrogen adsorption amount. The deteriorated performance of NDC-1 could be explained by such effects, where the nickel content is too low and can only offer very limited sites for spillover. The hydrogen uptake increases with the increase of nickel content; however, NDC-4 delivers worse performance than that of NDC-3. The same trend has been reported before, where a medium level of metal loading favors the best performance.8,14,40 The BET surface area of NDC-4 is 20% lower; the aggregation of nickel nanoparticles also has pronounced effects on hydrogen uptake. Although the crystallite size of NDC-4 in Table 1 changes only slightly, as shown in Figure 4c and 4d, the actual particle size is larger than this value. The aggregation phenomenon is more obvious for sample with a higher nickel content,40 which will reduce the efficiency of nickel nanoparticles. The lower surface area and aggregation of nickel nanoparticles should be the main reasons behind the hydrogen uptake drop of NDC-4. The enhancement of hydrogen adsorption by nickel loading varies greatly from one report to another.14,15,40 This apparent discrepancy could be caused by different factors, such as loading method, characteristics of porous adsorbents, or nickel content. The adsorption amount increase of 78% in this work is lower than some of the reported results; the relatively large nickel particle size (29−45 nm) might be the main cause.

NDC-3 demonstrate similar morphology and keep the basic structure characteristics of HMS. However, there are many more particles smaller than 300 nm in Figure 3b and 3c, which might be caused by the cracking of HMS and carbon composite particles during the carbonization or template removal process. TEM images of MC and NDC-3 are displayed in Figure 4.

Figure 4. TEM images of (a, b) MC and (c, d) NDC-3.

Figure 4a shows that MC consists of small particles forming larger aggregates, as also shown in the SEM images. A highly porous carbon matrix could be identified throughout the disordered wormhole-like structure in Figure 4b, with a pore diameter of approximate 1.5−3 nm. Dark spots in Figure 4c are observed for nickel nanoparticles, which are embedded in the porous carbon matrix. The particle size counted from Figure 4c is in the range of 29−45 nm. Figure 4d shows a nickel particle with a diameter of 42 nm. Since its diameter is much larger than the pore size of carbon, many different surrounding pores could be blocked by one single nickel particle at the same time, which should be the reason for the sharp surface area drop after nickel decoration. Figure 5 shows the hydrogen adsorption isotherms of MC and NDC samples at room temperature (295 K). A nearly linear relationship between adsorption amount and pressure is observed, a feature also reported for precious metal-decorated D

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Linkers: A Computational Study of the Factors That Control Binding Strength. J. Am. Chem. Soc. 2014, 136, 17827−17835. (8) Wang, L.; Yang, R. T. New Sorbents for Hydrogen Storage by Hydrogen Spillover - a Review. Energy Environ. Sci. 2008, 1, 268−279. (9) Stadie, N. P.; Vajo, J. J.; Cumberland, R. W.; Wilson, A. A.; Ahn, C. C.; Fultz, B. Zeolite-Templated Carbon Materials for High-Pressure Hydrogen Storage. Langmuir 2012, 28, 10057−10063. (10) Chen, H.; Yang, R. T. Catalytic Effects of TiF3 on Hydrogen Spillover on Pt/Carbon for Hydrogen Storage. Langmuir 2010, 26, 15394−15398. (11) Masika, E.; Bourne, R. A.; Chamberlain, T. W.; Mokaya, R. Supercritical CO2 Mediated Incorporation of Pd onto Templated Carbons: A Route to Optimizing the Pd Particle Size and Hydrogen Uptake Density. ACS Appl. Mater. Interfaces 2013, 5, 5639−5647. (12) Saha, D.; Deng, S. Hydrogen Adsorption on Pd- and Ru-Doped C60 Fullerene at an Ambient Temperature. Langmuir 2011, 27, 6780− 6786. (13) Carraro, P.; Elías, V.; Blanco, A. A. G.; Sapag, K.; Eimer, G.; Oliva, M. Study of Hydrogen Adsorption Properties on MCM-41 Mesoporous Materials Modified with Nickel. Int. J. Hydrogen Energy 2014, 39, 8749−8753. (14) Lin, K.-Y.; Tsai, W.-T.; Yang, T.-J. Effect of Ni Nanoparticle Distribution on Hydrogen Uptake in Carbon Nanotubes. J. Power Sources 2011, 196, 3389−3394. (15) Giraudet, S.; Zhu, Z. Hydrogen Adsorption in Nitrogen Enriched Ordered Mesoporous Carbons Doped with Nickel Nanoparticles. Carbon 2011, 49, 398−405. (16) Pevzner, S.; Pri-Bar, I.; Lutzky, I.; Ben-Yehuda, E.; Ruse, E.; Regev, O. Carbon Allotropes Accelerate Hydrogenation Via Spillover Mechanism. J. Phys. Chem. C 2014, 118, 27164−27169. (17) Wang, H.; Gao, Q.; Hu, J. High Hydrogen Storage Capacity of Porous Carbons Prepared by Using Activated Carbon. J. Am. Chem. Soc. 2009, 131, 7016−7022. (18) Liang, C.; Li, Z.; Dai, S. Mesoporous Carbon Materials: Synthesis and Modification. Angew. Chem., Int. Ed. 2008, 47, 3696− 3717. (19) Enterria, M.; Castro-Muniz, A.; Suarez-Garcia, F.; MartinezAlonso, A.; Tascon, J. M. D.; Kyotani, T. Effects of the Mesostructural Order on the Electrochemical Performance of Hierarchical MicroMesoporous Carbons. J. Mater. Chem. A 2014, 2, 12023−12030. (20) Zhai, Y.; Dou, Y.; Liu, X.; Park, S. S.; Ha, C.-S.; Zhao, D. SoftTemplate Synthesis of Ordered Mesoporous Carbon/Nanoparticle Nickel Composites with a High Surface Area. Carbon 2011, 49, 545− 555. (21) Casco, M. E.; Martínez-Escandell, M.; Gadea-Ramos, E.; Kaneko, K.; Silvestre-Albero, J.; Rodríguez-Reinoso, F. High-Pressure Methane Storage in Porous Materials: Are Carbon Materials in the Pole Position? Chem. Mater. 2015, 27, 959−964. (22) Gong, Y.; Wei, Z.; Wang, J.; Zhang, P.; Li, H.; Wang, Y. Design and Fabrication of Hierarchically Porous Carbon with a Template-Free Method. Sci. Rep. 2014, 4, 6349/1−6349/6. (23) Ji, X.; Lee, K. T.; Nazar, L. F. A Highly Ordered Nanostructured Carbon-Sulphur Cathode for Lithium-Sulphur Batteries. Nat. Mater. 2009, 8, 500−506. (24) Ryoo, R.; Joo, S. H.; Jun, S. Synthesis of Highly Ordered Carbon Molecular Sieves Via Template-Mediated Structural Transformation. J. Phys. Chem. B 1999, 103, 7743−7746. (25) Jun, S.; Joo, S. H.; Ryoo, R.; Kruk, M.; Jaroniec, M.; Liu, Z.; Ohsuna, T.; Terasaki, O. Synthesis of New, Nanoporous Carbon with Hexagonally Ordered Mesostructure. J. Am. Chem. Soc. 2000, 122, 10712−10713. (26) Sevilla, M.; Alvarez, S.; Fuertes, A. B. Synthesis and Characterisation of Mesoporous Carbons of Large Textural Porosity and Tunable Pore Size by Templating Mesostructured HMS Silica Materials. Microporous Mesoporous Mater. 2004, 74, 49−58. (27) Liu, R.; Shi, Y.; Wan, Y.; Meng, Y.; Zhang, F.; Gu, D.; Chen, Z.; Tu, B.; Zhao, D. Triconstituent Co-Assembly to Ordered Mesostructured Polymer−Silica and Carbon−Silica Nanocomposites and Large-

CONCLUSIONS In summary, highly porous mesoporous carbon has been prepared with HMS as hard template and resol as carbon precursors. After a systematic optimization of the synthesis process, a BET surface area of 2644 m2/g is achieved, which is better than some of the highest results reported so far for silicatemplated carbons to the best of our knowledge. The obtained carbon material has a hierarchically porous structure, with a micropore volume and mesopore volume of 0.58 and 0.74 cm3/ g, respectively. The carbon could be loaded with nickel nanoparticles simultaneously with the carbonization process. Although nickel decoration causes a drastic decrease of both the surface area and the pore volume, the adsorption amount at room temperature is enhanced. NDC-3 with a medium nickel content shows an improvement of 78% compared to the pristine carbon material.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpcc.5b06049. Figures for the change of reactants during mixing, SAXRD patterns, tables for the optimization of preparation of MC, and comparison of the specific surface area results of different carbons (PDF)

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AUTHOR INFORMATION

Corresponding Author

*Phone/fax: +86-755-26036729. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors are extremely grateful to the National Key Basic Research Program (no. 2013CB933103), funded by MOST, and the Program for Fundamental Research Supported by Shenzhen Science and Technology Innovations Council of China (grant nos. JSF201006300047A, JC201105201126A, and ZDSY20120619140933512).

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REFERENCES

(1) Yan, Y.; Yang, S.; Blake, A. J.; Schröder, M. Studies on Metal− Organic Frameworks of Cu(II) with Isophthalate Linkers for Hydrogen Storage. Acc. Chem. Res. 2014, 47, 296−307. (2) Mendoza-Cortes, J. L.; Goddard, W. A.; Furukawa, H.; Yaghi, O. M. A Covalent Organic Framework That Exceeds the DOE 2015 Volumetric Target for H2 Uptake at 298 K. J. Phys. Chem. Lett. 2012, 3, 2671−2675. (3) Stuckert, N. R.; Wang, L.; Yang, R. T. Characteristics of Hydrogen Storage by Spillover on Pt-Doped Carbon and CatalystBridged Metal Organic Framework. Langmuir 2010, 26, 11963− 11971. (4) Zhao, Y.-C.; Wang, T.; Zhang, L.-M.; Cui, Y.; Han, B.-H. Facile Approach to Preparing Microporous Organic Polymers through Benzoin Condensation. ACS Appl. Mater. Interfaces 2012, 4, 6975− 6981. (5) Sevilla, M.; Mokaya, R. Energy Storage Applications of Activated Carbons: Supercapacitors and Hydrogen Storage. Energy Environ. Sci. 2014, 7, 1250−1280. (6) Jena, P. Materials for Hydrogen Storage: Past, Present, and Future. J. Phys. Chem. Lett. 2011, 2, 206−211. (7) Tsivion, E.; Long, J. R.; Head-Gordon, M. Hydrogen Physisorption on Metal−Organic Framework Linkers and Metalated E

DOI: 10.1021/acs.jpcc.5b06049 J. Phys. Chem. C XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry C Pore Mesoporous Carbons with High Surface Areas. J. Am. Chem. Soc. 2006, 128, 11652−11662. (28) He, G.; Mandlmeier, B.; Schuster, J.; Nazar, L. F.; Bein, T. Bimodal Mesoporous Carbon Nanofibers with High Porosity: Freestanding and Embedded in Membranes for Lithium−Sulfur Batteries. Chem. Mater. 2014, 26, 3879−3886. (29) Park, J.-B.; Lee, J.; Yoon, C. S.; Sun, Y.-K. Ordered Mesoporous Carbon Electrodes for Li−O2 Batteries. ACS Appl. Mater. Interfaces 2013, 5, 13426−13431. (30) Tanev, P. T.; Pinnavaia, T. J. Mesoporous Silica Molecular Sieves Prepared by Ionic and Neutral Surfactant Templating: A Comparison of Physical Properties. Chem. Mater. 1996, 8, 2068−2079. (31) Chang, Y.; Antonietti, M.; Fellinger, T.-P. Synthesis of Nanostructured Carbon through Ionothermal Carbonization of Common Organic Solvents and Solutions. Angew. Chem., Int. Ed. 2015, 54, 5507−5512. (32) Li, J.; Wu, E. Adsorption of Hydrogen on Porous Materials of Activated Carbon and Zeolite NaX Crossover Critical Temperature. J. Supercrit. Fluids 2009, 49, 196−202. (33) Tanev, P. T.; Pinnavaia, T. J. A Neutral Templating Route to Mesoporous Molecular Sieves. Science 1995, 267, 865−867. (34) Kim, S.-S.; Pauly, T. R.; Pinnavaia, T. J. Non-Ionic Surfactant Assembly of Wormhole Silica Molecular Sieves from Water Soluble Silicates. Chem. Commun. 2000, 835−836. (35) Kim, H.-S.; Lee, H.; Han, K.-S.; Kim, J.-H.; Song, M.-S.; Park, M.-S.; Lee, J.-Y.; Kang, J.-K. Hydrogen Storage in Ni NanoparticleDispersed Multiwalled Carbon Nanotubes. J. Phys. Chem. B 2005, 109, 8983−8986. (36) Wang, L.; Yang, R. T. Hydrogen Storage Properties of Carbons Doped with Ruthenium, Platinum, and Nickel Nanoparticles. J. Phys. Chem. C 2008, 112, 12486−12494. (37) Cai, J.; Qi, J.; Yang, C.; Zhao, X. Poly(Vinylidene Chloride)Based Carbon with Ultrahigh Microporosity and Outstanding Performance for CH4 and H2 Storage and CO2 Capture. ACS Appl. Mater. Interfaces 2014, 6, 3703−3711. (38) Kruk, M.; Jaroniec, M. Gas Adsorption Characterization of Ordered Organic−Inorganic Nanocomposite Materials. Chem. Mater. 2001, 13, 3169−3183. (39) Wang, L.; Stuckert, N. R.; Chen, H.; Yang, R. T. Effects of Pt Particle Size on Hydrogen Storage on Pt-Doped Metal−Organic Framework IRMOF-8. J. Phys. Chem. C 2011, 115, 4793−4799. (40) Kim, B.-J.; Lee, Y.-S.; Park, S.-J. A Study on the Hydrogen Storage Capacity of Ni-Plated Porous Carbon Nanofibers. Int. J. Hydrogen Energy 2008, 33, 4112−4115. (41) Huang, C.-C.; Li, Y.-H.; Wang, Y.-W.; Chen, C.-H. Hydrogen Storage in Cobalt-Embedded Ordered Mesoporous Carbon. Int. J. Hydrogen Energy 2013, 38, 3994−4002.

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DOI: 10.1021/acs.jpcc.5b06049 J. Phys. Chem. C XXXX, XXX, XXX−XXX