Communication
RSC Advances
It is noteworthy that the sample activated at 600 uC is highly
moderate surface area and pore volume are required.
Furthermore, the templated carbon aerogels are amenable to
activation to generate very high surface area carbons.
2
21
microporous with ca. 85% (i.e. 1272 m g ) of the total surface
2
21
area (i.e. 1504 m g ) arising from micropores. The proportion of
micropore surface area decreases to 24% after activation at 800 uC.
Likewise the proportion of micropore volume decreases with
increase in activation temperature from 72% at 600 uC to 14% at
References
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2
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4
A. W. C. van den Bergm and C. O. Arean, Chem. Commun.,
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8
00 uC. Thus, where necessary, templating may be combined with
2
activation to further modify or optimise (with respect to surface
area, microporosity or mesoporosity) the textural properties of the
metal salt-templated carbon aerogels. To further clarify on the
general applicability of metal salts as porogens, we are currently
investigating a wide variety of metal salts. Early results indicate
that not all soluble metal salts can act as porogens; for example we
failed to generate porosity using ZnCl2.
4
2
7
5 (a) R. W. Pekala, J. Mater. Sci., 1989, 24, 3221; (b) F. M. Kong, J.
D. LeMay, S. S. Hulsey, C. T. Alviso and R. W. Pekala, J. Mater.
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The CO2 uptake capacity of the CaCl -templated carbon
2
aerogels was determined at ambient temperature and pressure
under flowing gas (pure CO
CO uptake of the carbons, which varies between 1.7 and 2.2
mmol g . This is a significantly high uptake when considered
against the surface area of the carbons as indicated by the uptake
density of 1.7 to 2.7 mmol m
despite the differences in textural properties indicates that the
pore size distribution, which is comparable for all three sample, is
5487.
2
) conditions. Table 1 summaries the
6
(a) B. Mathieu, S. Blacher, R. Pirard, J. P. Pirard, B. Sahouli and
F. Brouers, J. Non-Cryst. Solids, 1996, 212, 250; (b)
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R. Sobry and G. van den Bossche, J. Non-Cryst. Solids, 1998, 225,
2
21
2
2 3,13
.
The relatively similar uptake
8; (c) H. Tamon, H. Ishizaka, T. Yamamoto and T. Suzuki,
Carbon, 2000, 38, 1099; (d) M. Mirzaeian and P. J. Hall,
Electrochim. Acta, 2009, 54, 7444.
likely an important variable in determining uptake. The CO
uptake as a function of time (Fig. S2, ESI ) indicates that the rate of
2
7 (a) J. Biener, M. Stadermann, M. Suss, M. A. Worsley, M.
M. Biener, K. A. Rose and T. F. Baumann, Energy Environ. Sci.,
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S. Dresselhaus, Langmuir, 1996, 12, 6167.
3
uptake proceeds rapidly in the first few minutes and then
gradually slows to a smooth increase as it approaches equilibrium.
Maximum uptake is attained in ca. 50 min, which is comparable
to what has previously been observed for porous carbons under
8
(a) R. W. Pekala, J. C. Farmer, C. T. Alviso, T. D. Tran, S.
T. Mayer, J. M. Miller and B. Dunn, J. Non-Cryst. Solids, 1998,
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Mater., 2006, 18, 6087.
14
similar conditions. On the other hand, the CO
2
uptake of the
activated non-templated carbon aerogels varied between 1 and 2
21
3
mmol g (Table 2 and Fig. S3, ESI ), which is generally lower than
that of the templated carbon aerogels. Thus in the present case,
metal salt templating generates materials with overall superior
properties for CO uptake but via a much simpler and cheaper
2
route. The kinetics of CO uptake is also rather faster for the
2
templated carbon aerogels compared to the activated non-
9
(a) Y. Xia, Z. Yang and R. Mokaya, Nanoscale, 2010, 2, 639; (b)
Y. Xia, G. S. Walker, D. M. Grant and R. Mokaya, J. Am. Chem.
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Am. Chem. Soc., 2007, 129, 1673; (g) A. Pacula and R. Mokaya, J.
Phys. Chem. C, 2008, 112, 2764.
templated carbons (Fig. S2 and S3, ESI
illustrate the potential of metal salt templating as an alternative to
activation in generating carbon aerogels. Activation of the CaCl
3
). These observations
2
-
templated carbon aerogel Ca-CAMF800, at 600 and 800 uC
improves the CO uptake capacity only slightly from 2.2 mmol
2
21
21
g
to 2.5 and 2.6 mmol g , respectively (Table S1, ESI
3
). It is
however, clear that the increase in CO
2
uptake is proportionately
lower than the rise in surface area after activation because most of
the porosity generated during activation of the templated carbons
10 (a) C. Lin and J. A. Ritter, Carbon, 1997, 35, 1271; (b) C. Lin and
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F. P ´e rez-Cadenas, F. J. Maldonado-H o´ dar and F. Carrasco-
Mar ´ı n, Chem. Eng. J., 2012, 181, 851.
is in the mesopore range and thus not efficient for CO
2
4,15,16
uptake.
2
The activated CaCl -templated carbons that have
much higher surface may be more interesting for applications in
hydrogen storage or as electrode materials for supercapacitors,
which widens the potential appeal of the present carbon
11 K. S. W. Sing, D. H. Everett, R. A. W. Haul, L. Moscou, R.
A. Pierotti, J. Rouquerol and T. Siemieniewska, Pure Appl.
Chem., 1985, 57, 603–619.
17
aerogels.
1
2 (a) Y. Hanzawa, K. Kaneko, N. Yoshizawa, R. W. Pekala and M.
S. Dresselhaus, Adsorption, 1998, 4, 187; (b) T. Horikawa,
Y. Ono, J. Hayashi and K. Muroyama, Carbon, 2004, 42, 2683.
13 (a) G. P. Hao, W. C. Li and A. H. Lu, J. Mater. Chem., 2011, 21,
6447; (b) M. Sevilla, P. Valle-Vigon and A. B. Fuertes, Adv. Funct.
In conclusion, we have demonstrated the successful metal salt-
templated preparation of carbon aerogels via a simple subcritical
drying route. The metal salt (CaCl ) templating method offers an
2
alternative to activation, especially where carbon aerogels with
RSC Adv.
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