Performance of templated mesoporous carbons in supercapacitors

Abstract

By analogy with other types of carbons, templated mesoporous carbons (TMCs) can be used as supercapacitors. Their contribution arises essentially from the double layer capacity formed on their surface, which corresponds to 0.14 F m −2 in aqueous electrolytes such as H 2 SO 4 and KOH and 0.06 F m −2 for the aprotic medium (C 2 H 5 ) 4 NBF 4 in CH 3 CN. In the case of a series of 27 TMCs, it appears that the effective surface area determined by independent techniques can be as high as 1500-1600 m 2 g −1 , and therefore exceeds the value obtained for many activated carbons (typically 900-1300 m 2 g −1 ). On the other hand, the relatively low amount of surface oxygen in the present TMCs, as opposed to activated carbons, reduces the contribution of pseudo-capacitance effects and limits the gravimetric capacitance to 200-220 F g −1 for aqueous electrolytes. In the case of non-aqueous electrolyte, it rarely exceeds 100 F g −1 .It is also shown that the average mesopore diameter of these TMCs does not improve significantly the ionic mobility compared with typical activated carbons of pore-widths above 1.0-1.3 nm.This study suggests that activated carbons remain the more promising candidates for supercapacitors with high performances.

Correlation between heats of immersion and limiting capacitances in porous carbons

“…As discussed elsewhere [3,4,8] As shown elsewhere [6], immersion calorimetry into benzene and water also provides information on the total oxygen content of the surface,…”

“…It has been shown recently [6,8] that the limiting capacitance C o at low current density j (typically 1 mA cm -2 ) in acidic (2M H 2 SO 4 ) and aprotic (2)…”

“…Since the accessible surface area of the carbon and its oxygen content play a role in the specific capacitance, it is logical to correlate them with the information provided by immersion calorimetry and adsorption isotherms. The present study develops the approach outlined earlier [7][8][9][10][11] and shows that a good assessment of the gravimetric capacitance at low current densities can be achieved on the basis of immersion calorimetry. Both properties, given respectively in F g -1 and J g -1 , are related to the unit weight of carbon as opposed to other studies more oriented towards the study of surface related capacitances, such as Chmiola et al [12,13] …”

Correlation between capacitances of porous carbons in acidic and aprotic EDLC electrolytes

“…The comparative EDLC study is based on a total of 30 microporous carbons [3] and 5 templated mesoporous carbons [2,4,5], as well as a high surface area graphite (HSAG-300) [2]. As discussed in detail [6], a reliable determination of the surface areas of the carbons is essential for the study of EDLC properties in carbons.…”

“…(C 2 H 5 ) 4 NBF 4 in acetonitrile or propylene carbonate) media. A number of useful correlations have been established so far, relating their electrical double layer capacitance (EDLC) to structural and chemical properties of the carbons [1][2][3][4]. For example, it has been shown recently that in the 2 M aqueous H 2 SO 4 electrolyte the specific capacitance depends on a contribution from the total surface area S tot (the sum of the micropore and external areas) and from oxygen-containing surface groups [3].…”