Morphological reason for enhancement of electrochemical double layer capacitances of various acetylene blacks by electrochemical polarization

Kim, Taegon; Rhee, Choong Kyun; Yoon, Seong Ho; Tsuji, Masaharu; Mochida, Isao

doi:10.1016/j.electacta.2008.03.057

Cited by 11 publications

(7 citation statements)

References 34 publications

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“…It is said that a lot of functional groups, such as carboxyl groups, are on the surface of the KB used in sample 1. 22,23 According to the calculation based on molecular dynamics, it was suggested that ionized carboxyl groups on the carbon surface strongly interacted with the sulfonic groups of Nafion and water. 24 In this study, such kind of functional groups might exist on the KB surface and have an affinity with the sulfonic groups of the ionomer as well as with those in Ref.…”

Section: Resultsmentioning

confidence: 99%

Analysis of Proton Transport in Pseudo Catalyst Layers

Iden

Ohma

Shinohara

2009

J. Electrochem. Soc.

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Analytical techniques were investigated for examining the influence of the ionomer network structure on proton transport in the catalyst layers of a polymer electrolyte fuel cell. Two samples were made with and without a pseudocatalyst layer (PCL) consisting of a carbon black support and an ionomer between two membranes. The overall resistance of the samples was evaluated with a hydrogen pump technique. The difference in resistance between them was mainly due to the proton-transport resistance of the PCL. Another technique of subtracting high frequency resistance from the overall resistance was also examined. Almost the same characteristics were obtained with both techniques. Using the former technique, the effective proton conductivity of PCLs with different carbon supports was investigated. The effective proton conductivities differed. An analysis of the difference revealed the following two possible causes. One is that the Bruggeman factor of the samples might have been affected by the state of ionomer coverage. Another is that the proton conductivities of the ionomer as bulk differed, which might have been due to a difference in water content attributable to the carbon supports.

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Section: Resultsmentioning

confidence: 99%

Analysis of Proton Transport in Pseudo Catalyst Layers

Iden

Ohma

Shinohara

2009

J. Electrochem. Soc.

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“…Compared with the cyclic voltammogram of a conventional Au disk electrode (Figure S1b in the Supporting Information), the current observed in the double layer region (−0.28 to +0.8 V) is fairly large, which may be due to electrochemical double layer charging of the carbon support (Figure S1c in the Supporting Information). Spontaneous deposition of Pt on Au nanoparticles induces a modification in the cyclic voltammogram of plain Au nanoparticles, depending on Pt concentration. When Pt concentration is lower than 10 −4 M, the modification is not significant (Figure , parts b and c).…”

Section: Resultsmentioning

confidence: 99%

Modification of Au Nanoparticles Dispersed on Carbon Support Using Spontaneous Deposition of Pt toward Formic Acid Oxidation

et al. 2010

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This work presents formic acid oxidation on Pt deposits on Au nanoparticles dispersed on Vulcan XC-72R. The Pt deposits were produced using spontaneous deposition method contacting the Au nanoparticles with solutions containing Pt complex ions in various concentrations. The Pt deposits were characterized using CO stripping coulometry, X-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectroscopy. When the Pt concentration is 10(-5)-10(-4) M, the Pt deposits are nanoislands of monatomic height. In the concentration range of 10(-4)-10(-3) M, the Pt deposits are most likely two-layer-thick nanofeatures. As Pt concentration increases further, the deposits become wider and thicker. Voltammetric behavior of Pt deposits reveals that on Pt deposits, dehydrogenation path is activated at the expense of poison-forming dehydration path. Furthermore, chronoamperometric measurement of the catalytic activity of Pt deposits supports that the two-layer-thick Pt deposits are most efficient in formic acid oxidation among the studied Pt deposits on Au nanoparticles. The enhancement factor of the particular Pt deposits is 2 in terms of turnover frequency, compared with a commercial Pt catalyst. Details are discussed in conjunction with Pt deposits on Au(111).

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“…[1][2][3] However, regardless of the high surface area, carbon materials exhibit much lower specific capacitances than expected, which is attributed to the relatively low surface area available to charge storage from poor wettability. 4 Therefore, considerable efforts have been made to modify the carbon materials (e.g., wet chemical, [3][4][5][6] dry chemical, [6][7][8] or electrochemical oxidation [9][10][11][12][13] ), to increase the double layer capacitance, which plays a predominant role in the overall capacitance; or occasionally to increase the pseudo-capacitance whose contribution is only 1-22%. 1,14,15 Up to now, the evident pseudo-capacitance of carbon materials has rarely been reported.…”

Section: Introductionmentioning

confidence: 99%

Reversible redox reaction on the oxygen-containing functional groups of an electrochemically modified graphite electrode for the pseudo-capacitance

Fan

et al. 2011

J. Mater. Chem.

113

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Reversible redox reactions on the oxygen-containing functional groups of an electrochemically modified graphite electrode (GE) by recurrent galvanic pulses in 2.3 M H 2 SO 4 solution are investigated. The crystal morphology, surface composition and electrochemical performance of electrochemically modified GE are monitored by scanning electron microscopy, Raman spectroscopy, nitrogen adsorption, Fourier transform infrared spectroscopy, thermogravimetry, Boehm's titration, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry (CV) tests. After the electrochemical modification, the material shows a turbostratic structure with many small domains consisting of multi-layered graphene sheets in parallel, and presents a high specific capacitance of 179.7 F g À1 , as well as a good stability after 10000 CV cycles. The high specific capacitance is mainly attributed to the continuous reversible redox reactions of the active groups among the hydroxyl (reduced state), carbonyl (half-oxidized state) and carboxyl (fully oxidized state) groups; a redox mechanism is obtained consequently. The amount of active groups on the modified GE surface is about 848-875 mmol g À1 by the Boehm titration. Their contribution to the pseudocapacitance according to the redox mechanism is about 130-140 F g À1 , which is consistent with the results of electrochemical measurements.

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Morphological reason for enhancement of electrochemical double layer capacitances of various acetylene blacks by electrochemical polarization

Cited by 11 publications

References 34 publications

Analysis of Proton Transport in Pseudo Catalyst Layers

Analysis of Proton Transport in Pseudo Catalyst Layers

Modification of Au Nanoparticles Dispersed on Carbon Support Using Spontaneous Deposition of Pt toward Formic Acid Oxidation

Reversible redox reaction on the oxygen-containing functional groups of an electrochemically modified graphite electrode for the pseudo-capacitance

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