The contribution of sulfate ions and protons to the specific capacitance of microporous carbon monoliths

Barranco, Violeta; García-Gómez, Alejandra; Kunowsky, Mirko; Linares‐Solano, A.; Ibáñez, Joaquı́n; King, Mackenzie; Rojo, J. M.

doi:10.1016/j.jpowsour.2014.03.114

Cited by 4 publications

(4 citation statements)

References 62 publications

(118 reference statements)

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“…In a previous study, the EDLC performances of the monoliths revealed high capacitances on a gravimetric, and exceptionally high capacitances on a volumetric basis . In a further study, the contribution of sulfate ions and protons to the specific capacitances have been studied in more detail . In the present work, these values are confirmed, comparing the results obtained in two‐ and three‐electrode configurations.…”

Section: Introductionsupporting

confidence: 79%

“…The specific capacitances of CM, CM‐N 2 , CM‐24, and CM‐48 are given in Table . The results were obtained from galvanostatic measurements in symmetric two‐electrode cells ( C s,2ec ) and three‐electrode cells ( C s,3ec ) for a low current density of 1 mA/cm 2 , that is, in nearly steady conditions . It can be observed that the values obtained in the two different setups are in very good agreement.…”

Section: Resultsmentioning

confidence: 91%

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Applications for CO₂‐Activated Carbon Monoliths: II. EDLC Electrodes

Kunowsky

Linares‐Solano

García-Gómez

et al. 2015

Int J Applied Ceramic Tech

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The use of high-density carbon monoliths (CM) for preparing supercapacitor electrodes is analyzed. The starting CMs, produced by ATMI Co, were treated as follows: (1) under a N 2 flow at 1073 K to modify the carbon surface chemistry and (2) activated with CO 2 at the same temperature, using different activation times, to increase their porosity. Electrochemical measurements were performed on disks of 1-2 mm thickness which are suitable for direct use in practical devices. Two-and three-electrode cells were used with 2 M H 2 SO 4 solution as electrolyte. The contents of surface oxygen groups were measured by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). The porosity of the starting monolith is increased by physical activation with CO 2 , the BET surface area increasing from 957 to 1684 m 2 /g. Upon heat treatments, both, the high density (1.2 g/cm 3 ), as well as the high amount of surface oxygen groups (2411 lmol CO/g) of the starting monolith are reduced; however, the densities of the treated monoliths remain higher than values reported for other porous carbon monoliths. The performance of the CMs as supercapacitor electrodes show as follows: (1) high specific and exceptionally high volumetric capacitances (up to 292 F/g and 342 F/cm 3 , respectively) due to their appropriate structure, porosity, and density, (2) a long and stable cyclability, (3) a decrease of power density with disk thickness, and (4) a decrease of pseudocapacitance with activation time.

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Section: Introductionsupporting

confidence: 79%

Section: Resultsmentioning

confidence: 91%

Applications for CO₂‐Activated Carbon Monoliths: II. EDLC Electrodes

Kunowsky

Linares‐Solano

García-Gómez

et al. 2015

Int J Applied Ceramic Tech

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“…In the literature, including a previous paper of some of the present authors, oftentimes SO 4 2− and H 3 O + are reported as the dominant ions for the aqueous solution of sulfuric acid . However, this is inaccurate due to the fact that the dissociation of sulfuric acid in water involves two stages.…”

Section: Resultsmentioning

confidence: 75%

New Carbon Monoliths for Supercapacitor Electrodes. Looking at the Double Layer

et al. 2017

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Carbon monoliths are prepared by combining two carbon phases. A major phase is activated anthracite, which provides microporosity and a large surface area. The other phase is a carbonized polymer that provides self-consistency and contributes to densifying the monolith. Different degrees of anthracite activation and different contents of the two phases are investigated. These all-carbon monoliths have surface areas up to 2600 m 2 g À1 , mechanical strengths up to 6 MPa, electrical conductivities up to 2-4 S cm À1 , and densities between 0.4 and 0.7 g cm À3 . In sulfuric acid electrolyte, gravimetric capacitances up to 307 F g À1 are achieved. The double-layer capacitances due to the hydronium and bisulfate ions are separately measured, the former being approximately 25% higher than the latter. The size of the two ions electro-adsorbed at the double layer is discussed. The pseudocapacitance associated with the hydronium ion is 10-25% of the total capacitance of this ion. All of the carbon monoliths show high capacitance retention with current density; the retention of the double-layer capacitance is similar for the two types of ions and higher than the retention of the pseudocapacitance associated with the hydronium ion.

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“…Advanced analyses of the isotherms based on Density Functional Theory (DFT) [4,81,82] have been proposed to provide areas taking into account the ions dimensions [83][84][85]. With the help of the software of commercial adsorption equipments, the pore size distribution of nanoporous carbons is assessed and, subsequently, the surface area involved in charge storage is calculated by subtracting that in pores smaller than the ions size.…”

Section: Surface Area Accessible To Electrolyte Ionsmentioning

confidence: 99%

Capacitance and surface of carbons in supercapacitors

Lobato

Suárez

Guardia

et al. 2017

Carbon

123

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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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The contribution of sulfate ions and protons to the specific capacitance of microporous carbon monoliths

Cited by 4 publications

References 62 publications

Applications for CO₂‐Activated Carbon Monoliths: II. EDLC Electrodes

Applications for CO₂‐Activated Carbon Monoliths: II. EDLC Electrodes

New Carbon Monoliths for Supercapacitor Electrodes. Looking at the Double Layer

Capacitance and surface of carbons in supercapacitors

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The contribution of sulfate ions and protons to the specific capacitance of microporous carbon monoliths

Cited by 4 publications

References 62 publications

Applications for CO2‐Activated Carbon Monoliths: II. EDLC Electrodes

Applications for CO2‐Activated Carbon Monoliths: II. EDLC Electrodes

New Carbon Monoliths for Supercapacitor Electrodes. Looking at the Double Layer

Capacitance and surface of carbons in supercapacitors

Contact Info

Product

Resources

About

Applications for CO₂‐Activated Carbon Monoliths: II. EDLC Electrodes

Applications for CO₂‐Activated Carbon Monoliths: II. EDLC Electrodes