Closure to “Discussion of ‘Adsorption and Oxidation of Butane on Platinum Black in H[sub 2]SO[sub 4]’ [J. A. Shropshire and H. H. Horowitz (pp. 490–492, Vol. 113, No. 5)]”

Shropshire, J. A.; Horowitz, H. H.

doi:10.1149/1.2423838

Cited by 7 publications

(16 citation statements)

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“…Propane adsorption on platinum in phosphoric acid has been studied (14,15), but since the adsorption process was diffusion-controlled, no rate expressions could be derived from those results. Butane adsorption on platinum in sulfuric acid has been measured at steady state by tracer methods (16), and under unsteady-state conditions by the use of flow-through porous electrodes (17); neither investigation yielded quantitative kinetic information.…”

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confidence: 99%

The Kinetics of Propane Adsorption on Platinum in Hydrofluoric Acid

Cairns

Breitenstein

1967

J. Electrochem. Soc.

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As a first stage in the investigation of the electrochemical oxidation of saturated hydrocarbons on platinum in acid electrolytes, the rate of adsorption of propane on a smooth platinum electrode was studied at 90~ in 37 mole % HF. Using an all-PTFE apparatus and single linear voltage sweep techniques, the surface coverage by hydrocarbon species was measured as a function of adsorption time and potential. The steady-state coverage resulting from propane adsorption shows a sharp maximum at 0.2v (vs. rhe). The amount of the most electrochemically active species is highest at 0.3v. The adsorption rate follows Langmuir kinetics with a third-order dependence on free surface. The rate constant has been measured for 0.2 and 0.3v at 90~During the last few years there has been an active interest in the direct anodic oxidation of saturated hydrocarbons in fuel cells (1-10). Exploratory fuel cell investigations pointed out the usefulness of strong acid electrolytes in this connection. The acidic electrolytes which have received the most attention in hydrocarbon fuel cells are ,sulfuric acid (1), phosphoric acid (2-4), hydrofluoric acid (5-8), and cesium fluoride-hydrofluoric acid mixtures (5,6,9,10). In order to understand better the kinetics and mechanisms involved in the over-all process of anodic oxidation of hydrocarbons, it is desirable to study the various individual steps in the process, starting with the adsorption of the hydrocarbon on a suitable electrode material in the presence of electrolyte.Some work on the adsorption of methane (11) and ethane (12, 13) on platinum in perchloric acid has been done at temperatures below those where significant reactivity is shown in fuel cells. The results of Gilman (12) on ethane adsorption on platinum in perchloric acid were interpreted in terms of the kinetics of the adsorption process, the adsorption being second order in free surface and first order in ethane concentration. Propane adsorption on platinum in phosphoric acid has been studied (14, 15), but since the adsorption process was diffusion-controlled, no rate expressions could be derived from those results. Butane adsorption on platinum in sulfuric acid has been measured at steady state by tracer methods (16), and under unsteady-state conditions by the use of flow-through porous electrodes (17); neither investigation yielded quantitative kinetic information.In order to study the kinetics of the adsorption process, it is necessary to perform the adsorption experiments under conditions where diffusion is not controlling. This requires that the product of the concentration of dissolved hydrocarbon and its diffusion coefficient be large enough (and therefore, diffusion fast enough) that the adsorption step is the slower process. It is known that hydrofluoric acid enhances the solubility of saturated hydrocarbons in water (18), and it is expected that the fluoride anion is not adsorbed on platinum electrodes (19,20). For these reasons and because of the fact that fuel cells using hydrofluoric acid electrolyte oxidize satu...

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confidence: 99%

The Kinetics of Propane Adsorption on Platinum in Hydrofluoric Acid

Cairns

Breitenstein

1967

J. Electrochem. Soc.

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“…Our results indicate that methane adsorption reaches a maximum at 0.3 V, in agreement with previous studies of short chain alkane adsorption in acidic electrolytes. 36,38,39 While the maximum adsorption potential is within the range…”

Section: Potential Dependence Of Methane Adsorptionmentioning

confidence: 99%

Determining the potential-dependent identity of methane adsorbates at Pt electrodes using EC-MS

Lucky,

Fuller,

Schreier

2024

Catal. Sci. Technol.

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“…The literature devoted to the anodic adsorption and oxidation of hydrocarbons is extensive (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) and a variety of studies based on steady-state experimental data and nonsteady-state have been investigated. Various techniques have long been available for the measurement of coverage of adsorbed species on solid electrodes.…”

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confidence: 99%