Correlation between heats of immersion and limiting capacitances in porous carbons

Centeno, Teresa A.; Fernández, Julio César; Stoeckli, Fritz

doi:10.1016/j.carbon.2008.03.005

Cited by 24 publications

(19 citation statements)

References 26 publications

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“…As shown earlier [15,16], the DFT-based pore size distributions indicate a sharp drop around 0.6-0.7 nm, which suggests that there are no pores below this size. Moreover, the ratios of the enthalpies of immersion into CCl 4 and C 6 H 6 (Table 1) are close to 0.96, the value expected for equal accessibility of the micropores to both liquids [25]. This confirms that the same surface area is accessible to nitrogen, benzene, CCl 4 and the different electrolytes (carbon tetrachloride, with a critical diameter of approximately 0.65 nm, is obviously a convenient analogue for the (C 2 H 5 ) 4 N + ion (0.68 nm) [14]).…”

Section: Resultssupporting

confidence: 55%

EDLC performance of carbide-derived carbons in aprotic and acidic electrolytes

Fernández

Arulepp

Leis

et al. 2008

Electrochimica Acta

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a b s t r a c tThis study shows that carbide-derived carbons (CDCs) with average pore size distributions around 0.9-1 nm and effective surface areas of 1300-1400 m 2 g −1 provide electrochemical double-layer capacitors with high performances in both aqueous (2M H 2 SO 4 ) and aprotic (1M (C 2 H 5 ) 4 NBF 4 in acetonitrile) electrolytes.In the acidic electrolytic solution, the gravimetric capacitance at low current density (1 mA cm −2 ) can exceed 200 F g −1 , whereas the volumetric capacitance reaches 90 F cm −3 . In the aprotic electrolyte they reach 150 F g −1 and 60 F cm −3 . A detailed comparison of the capacitive behaviour of CDCs at high current density (up to 100 mA cm −2 ) with other microporous and mesoporous carbons indicates better rate capabilities for the present materials in both electrolytes. This is due to the high surface area, the accessible porosity and the relatively low oxygen content.It also appears that the surface-related capacitances of the present CDCs in the aprotic electrolyte are in line with other carbons and show no anomalous behaviour.

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Section: Resultssupporting

confidence: 55%

EDLC performance of carbide-derived carbons in aprotic and acidic electrolytes

Fernández

Arulepp

Leis

et al. 2008

Electrochimica Acta

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“…The participation of oxygen functionalities was further confirmed by the good agreement observed between the experimental capacitances in H 2 SO 4 and those calculated from the enthalpies of immersion of carbons into benzene and water [32].…”

Section: Determination Of the Electrochemical Capacitancesupporting

confidence: 63%

“…Recent results based on the combination of N 2 -physisorption and immersion calorimetry into CH 2 Cl 2 (0.33 nm), C 6 H 6 (0.41 nm) and CCl 4 (0.63 nm) reported that the surface accessible to Et 4 N + was reduced by 20-27 % with respect to the total surface area of carbon monoliths electrodes[47].So far, the most selective physisorption based-approach to assess the surface involved in charges storage is the use of molecules suiting the critical dimension of ions. With the help of carbon tetrachloride (0.63 nm) and norbornadiene (0.65 nm) as convenient probes[6,32,38] for the reliable assessment of the surface area accessible to the cation Et 4 N + ,Figure 3aclearly illustrates that the total surface of a variety of activated carbons is not perceptible for the organic electrolyte. This is particularly remarkable for carbon HK-650-8 with an average micropore size of 0.66 nm, in which Et 4 N + is excluded from 63% of its surface area.…”

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confidence: 99%

Capacitance and surface of carbons in supercapacitors

Lobato

Suárez

Guardia

et al. 2017

Carbon

124

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This research is focused in the missing link between the specific surface area of carbons surface and their electrochemical capacitance. Current protocols used for the characterization of carbons applied in supercapacitors electrodes induce inconsistencies in the values of the interfacial capacitance (in F m-2), which is hindering the optimization of supercapacitors. The constraints of both the physisorption of N 2 at 77 K and the standard methods used for the isotherm analysis frequently lead to a misleading picture of the porosity. Moreover, the specific surface area of carbons loses their meaning when the supercapacitor operates with organic electrolytes and ionic liquids and the actual surface involved in charge storage has to be assessed by molecular probes suiting the critical dimensions of the ions. In the case of certain carbons such as graphene type-materials, the voltage-driven mechanism may facilitate the access of electrolyte ions to spaces between carbon layers, providing a larger area than that estimated by gas adsorption. Finally, the morphological and porous features of carbons can be extremely modified when they are processed in electrodes. Due to their impact, all these issues should not be neglected and the characterization protocols must be adapted for this specific application of carbons.

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“…In the case of aprotic electrolytes with bulkier ions (e.g. (C 2 H 5 ) 4 NBF 4 in acetonitrile) and ionic liquids such as EMI-TFSI, the accessibility of the micropores may be considerably reduced for carbons with narrow pores (width < 0.7 nm) or showing 'gate' effects at the pores entrance [2,7,9,10]. On the other hand, the contribution from pseudocapacitance effects in the (C 2 H 5 ) 4 NBF 4 /acetonitrile electrolyte appears to be negligible compared to the aqueous media and the supercapacitor performance is essentially based on a double-layer mechanism through the extent of the accessible (effective) surface area of the carbon [2,9,10].…”

Section: Introductionmentioning

confidence: 99%

Effect of mesoporosity on specific capacitance of carbons

Fernández

Tennison

Kozynchenko

et al. 2009

Carbon

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The study compares the structural and electrochemical properties of 12 porous carbons based on phenolic resins, using both aqueous (H 2 SO 4) and aprotic ((C 2 H 5) 4 NBF 4 in acetonitrile) electrolytes. It appears that they fit into the general pattern observed for other carbons. The present carbons have micropore volumes varying between 0.29 and 0.66 cm 3 g-1 and average pore widths L o between 0.62 and 1.23 nm. Five samples are exclusively microporous, whereas seven also display a relatively important mesoporosity. This allows a direct comparison between pairs of carbons with similar micropore systems, with and without mesopores, in order to assess the role of mesoporosity in the electrochemical properties. It appears that mesopores have only a limited influence on the decrease in capacitance at high current density as opposed to earlier assumptions.

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Correlation between heats of immersion and limiting capacitances in porous carbons

Cited by 24 publications

References 26 publications

EDLC performance of carbide-derived carbons in aprotic and acidic electrolytes

EDLC performance of carbide-derived carbons in aprotic and acidic electrolytes

Capacitance and surface of carbons in supercapacitors

Effect of mesoporosity on specific capacitance of carbons

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