Double layer capacity and methanol coverage on platinum in perchloric acid solution

Bréiter, M.W.

doi:10.1016/0013-4686(62)85003-8

Cited by 27 publications

(12 citation statements)

References 15 publications

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“…This fact was taken to indicate the establishment of activation, rather than diffusion-controlled rates of reaction. This region of concentration is also that reported by Breiter (8) and Pavela (2) to be necessary to achieve saturated coverage of platinum electrodes in solutions of methanol. It may be noted in passing that the maximum current densities obtainable in these systems at moderate concentrations are considerably in excess of the limiting currents predicted by steady state diffusion calculations because of the convective stirring due to the evolution of carbon dioxide.…”

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confidence: 86%

The Electrochemical Oxidation of Formic Acid on Platinum

Fleischmann¹,

Johnson²,

Kuhn³

1964

J. Electrochem. Soc.

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The anodic oxidation of formic acid has been investigated on platinum black electrodes in 5N sulfuric acid. The data presented pertain to the activation controlled process under approximately steady state conditions at four temperatures between 25 ~ and 90~ Tafel plots appear to have significant slopes, and the correlation of these slopes with experimentally measured electrode coverages supports the hypothesis of two distinct electrochemical oxidation mechanisms, advanced by other workers.The electrochemical oxidation of formic acid has been studied by many workers (1-6), the most recent paper being one by Breiter (7) who studied electrode coverage and current-voltage relationships at ambient temperature with bright platinum electrodes. In the present work, coverage measurements and current-voltage data were obtained at four temperatures, 25 ~ 45 ~ 70 ~ and 90~ using platinized platinum electrodes in a 5N H2SO4-1M HCOOH solution.Although perchloric acid has frequently been used as an electrolyte for such work, it becomes an oxidizing agent at higher temperatures. With sulfuric acid, this effect is smaller.The choice of concentration of formic acid was based on the observation that the current in all potential regions ceased to be dependent on concentration somewhere between 0.5 and 1.0 molar on the type of electrodes investigated and at the highest temperatures employed. This fact was taken to indicate the establishment of activation, rather than diffusion-controlled rates of reaction. This region of concentration is also that reported by Breiter (8) and Pavela (2) to be necessary to achieve saturated coverage of platinum electrodes in solutions of methanol. It may be noted in passing that the maximum current densities obtainable in these systems at moderate concentrations are considerably in excess of the limiting currents predicted by steady state diffusion calculations because of the convective stirring due to the evolution of carbon dioxide.In view of Breiter's statement (for methanol) that extremely small amounts of hydrogen were observed on bright platinum electrodes at open circuit, while significant amounts of hydrogen have been measured in this work, the difference in the type of electrode is an important one. Schwabe (9) and others have measured the rate of heterogeneous decomposition of formic acid, using platinum black catalysts. ExperimentalMaterials and electrodes.--Reagent grade formic acid (98 Jr %, Eastman) and sulfuric acid (Baker) were used throughout the work.Platinized platinum electrodes were prepared from 0.003 in. platinum sheet. The plating solution was 1.7N HC1 containing 2.4 weight per cent Pt (as HfPtC16, Bishop) and a trace of lead acetate. Deposition of the black was carried out simultaneously on all electrodes at 10 ma/cm 2 for 3 min followed by 50 ma/cm e for 2 min. The resulting surfaces were smooth and uniformly black. The geometric area of the electrodes was 2 cm 2 for the work at room temperature but was decreased for the work at higher temperatures in order to provide currents...

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supporting

confidence: 86%

The Electrochemical Oxidation of Formic Acid on Platinum

Fleischmann¹,

Johnson²,

Kuhn³

1964

J. Electrochem. Soc.

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“…[1], were obtained by the following potential step method: a. [1], were obtained by the following potential step method: a.…”

Section: Kinetics Of Electrooxidation Of Adsorbed Speciesmentioning

confidence: 99%

“…The build-up of intermediates has been detected during the electrooxidation of methanol and formic acid (1,2), olefins (3), and, more recently, during the electrooxidation of saturated hydrocarbons (4, 5) on platinum electrodes. But the identities of the adsorbed species and the nature of the adsorption processes remain in doubt.…”

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confidence: 99%

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Adsorption and Oxidation of Ethane, n-Butane, and n-Octane on Platinum Electrodes

Aronowitz¹,

Flannery²

1969

J. Electrochem. Soc.

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Ethane, n-butane, and n-octane are adsorbed from aqueous sulfuric acid solutions onto platinum electrodes at 0.25-0.55V vs. NHE. At potentials higher than 0.30V how fast the surface coverage builds up depends on both the rate of adsorption and the rate of anodic oxidation. At 0.25-0.30V adsorption can be studied independently. Rate data show that adsorption is potential independent and first order in apparent uncovered surface area. Studies of the kinetics of anodic oxidation and studies of hydrogen codeposition indicate that the adsorbed species are similar for ethane and n-octane but differ for n-butane adsorption.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-04-02 to IP Phys. Chem., 69, 3335 (1965).) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-04-02 to IP

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“…An essentially linear dependence of the exchange activation enthalpy upon bond strength in the haloacetic acid series has been previously noted. 6 The difference in the exchange enthalpies for the chloroacetic acid and chloroacetate systems has been interpreted as due to electrostatic effects.1 (The difference, approximately 2.4 kcal. mole-1, is equivalent to the work done in bringing together two unit charges in water at 80°to a distance of 2 A.…”

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confidence: 99%