The Kinetics of Adsorption, Surface Reaction, and Electrochemical Oxidation of Propane on Platinum in Hydrofluoric Acid

Cairns, Elton J.; Breitenstein, Adrian M.; Scarpellino, A. J.

doi:10.1149/1.2411340

Cited by 10 publications

(3 citation statements)

References 16 publications

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“…where the parentheses denote the different adsorbed species. The possibility that the different adsorbed species may be linked through interconversion surface processes can be formally expressed in the following way (C2H2) - Reactions [2a] and [2b] are comprised within the reaction formalism earlier proposed for the surface reactions taking part in the electrooxidation of propane on platinum in 37 mol percent HF at 90~ (24,25). Otherwise, reaction [2c] has been recently postulated to interpret the cathodic hydrogenation of one of the species formed during the electrosorption of methane in 1N H~SO4 at 60~ (22).…”

Section: Discussionmentioning

confidence: 99%

The Electrosorption and the Potentiodynamic Electrooxidation of Ethane on Platinum at Different Temperatures

Solı́s

Luna

Triaca

et al. 1981

J. Electrochem. Soc.

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The electrosorption and the potentiodynamic electrooxidation of ethane on platinized platinum in 1N H2SO4 has been studied in the 20°–80°C range. The potentiodynamic I/E profiles run immediately after the potentiostatic electrosorption of the hydrocarbon show that three different species participate in the electrooxidation process. The various electrosorbed species are tentatively related to the electrosorbed species which are formed during the electrosorption of both methane and ethylene on platinum. The electrochemical process is discussed through a complex reaction pathway involving electrosorption, interconversion, and electrooxidation processes.

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Section: Discussionmentioning

confidence: 99%

The Electrosorption and the Potentiodynamic Electrooxidation of Ethane on Platinum at Different Temperatures

Solı́s

Luna

Triaca

et al. 1981

J. Electrochem. Soc.

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“…It was proposed [7] that the hydrocarbon is dissociatively chemisorbed to form an adsorbed hydrogen atom and a carbonaceous species that subsequently dehydrogenates forming additional hydrogen atoms and other surface species that ultimately either convert to CO 2 or oligomerize to form a carbonaceous residue on the electrode surface. An alternative mechanism [8] suggested that the rate determining step was the chemical reaction between an adsorbed hydrocarbon (acetylene) and an adsorbed OH species that resulted from water dissociation.…”

Section: Several Other Factors Influence the Performance Ofmentioning

confidence: 99%

Mathematical model for a direct propane phosphoric acid fuel cell

et al. 2005

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A mathematical model was developed and used to predict the performance of direct propane phosphoric acid (PPAFC) fuel cells, utilizing both Pt/C state-of the-art electrodes and older Pt black electrodes. It was found that the overpotential caused by surface processes on the platinum catalyst in the anode is much greater than the potential losses caused by either ohmic resistance or propane diffusion in gas-filled and liquid-filled pores. In one comparison, the anode overpotential (0.5 V) was larger than the cathode overpotential (0.3 V) at a current density of 0.4 A cm )2 for Pt loadings 4 mg Pt cm )2 . The need for sufficient water concentration at the anode, where water is a reactant, was indicated by the large effect of H 3 PO 4 concentration. In another comparison, the model predicted that at 0.2 A cm )2 , modern carbon supported Pt catalysts would produce 0.35 V compared to 0.1 V for unsupported Pt black catalysts that were used several decades ago, when the majority of the research on direct hydrocarbon fuel cells was performed. The propane anode and oxygen cathode catalyst layers were modeled as agglomerates of spherical catalyst particles having their interior spaces filled with liquid electrolyte and being surrounded by gasfilled pores. The Tafel equation was used to describe the electrochemical reactions. The model incorporated gas and liquid-phase diffusion equations for the reactants in the anode and cathode and ionic transport in the electrolyte. Experimental data were used for propane and oxygen diffusivities, and for their solubilities in the electrolyte. The accuracy of the predicted electrical potentials and polarization curves were normally within ±0.02 V of values reported in experimental investigations of temperature and electrolyte concentration. Polarization curves were predicted as a function of temperature, pressure, electrolyte concentration, and Pt loading. A performance of 0.45 V at 0.5 A cm )2 was predicted at some conditions.

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“…It is well known that these types of species are readily formed after the electro-oxidation of hydrocarbons on Pt electrodes. 33,42,43 In particular, based on electrochemical measurements, Brummer and Turner 44 suggested that the electro-oxidation of the propane on Pt electrodes followed a parallel scheme, in which the CH species ͑called type II by the authors͒ were not forerunners of the O-type species ͑type I͒ in a scheme C 3 H 8 → O-type → CO 2 . In the case of methanol oxidation, it was found from Fourier transform infrared ͑FTIR͒ measurements that COH is not necessarily formed a step ahead of CO on the route to CO 2 , but rather CO could be formed in a parallel path from a series of steps following the adsorption of methanol.…”

Section: Ionmentioning

confidence: 99%

Real-Time Mass Spectrometric Analysis of the Anode Exhaust Gases of a Direct Propane Fuel Cell

Rodríguez-Varela

Savadogo

2005

J. Electrochem. Soc.

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The exhaust gases composition of a direct propane fuel cell ͑DPFC͒ operating at 80°C was studied by mass spectrometric methods. Blank propane was introduced in the anode chamber without external reforming. The effect of the anode catalysts on the composition of the exhaust gases was investigated. It was found that the mass spectra of the electro-oxidized propane presented significant differences compared to the mass spectra of the blank propane introduced directly into the mass spectrometer. It was found that the operation of the DPFC at 80°C involves several processes, i.e., adsorption, dehydrogenation, and C-C bond cleavage of the molecule. It was shown that the intensity of the peaks associated with species like CH 4 , CO, and C 2 H 4 increases with the polarization potential of the fuel cell. The opposite effect was found for the relative intensity of the molecular ion at m/z = 44, which decreased with the cell polarization potential. These spectrometric characteristics indicate that the composition of the anode exhaust gases is related to the polarization conditions. These results confirm that the direct propane electro-oxidation was responsible for the operation of the DPFC.We have reported the characteristics of a direct propane fuel cell ͑DPFC͒ operating at 80°C in previous works. 1-4 We have described the experimental setup and procedure, as well as the electrochemical behavior of several Pt-based anode electrocatalysts for the direct electro-oxidation of propane in DPFC. 1-4 Some of the anode materials tested in the DPFC are Pt-metal oxides which have shown a high catalytic activity for the electro-oxidation of propane. 1-4 Some of the investigations related to the development of direct propane fuel cells in our laboratory includes the use of mass spectrometry ͑MS͒ to analyze the composition of the outlet gases of the cell produced during the electrochemical oxidation of the propane in the fuel cell. This type of spectrometric experiments allows the detection of volatile products and intermediates which are produced during the electrochemical reaction of organic substances used to feed polymer electrolyte fuel cells ͑PEFC͒. 5 Thus, it is possible to determine the reaction mechanisms of a variety of substances under fuel cell operating conditions. In the case of carbonaceous organic molecules, the main interest in fuel cell applications is to achieve a complete oxidation of the substance to CO 2 with maximum conversion efficiencies.Integrated MS-electrochemical techniques have been used to analyze the electrochemical behavior of adsorbed species formed in fuel cell gas diffusion anodes in the presence of methanol, 5,6 trimethoxymethane, 7 and formic acid. 8 Using the method of differential electrochemical mass spectrometry ͑DEMS͒, it was possible to detect CO 2 as some reaction products of the catalytic oxidation of small organic molecules on Pt-based electrocatalysts. 9,10 DEMS techniques have also been used to investigate the oxidation processes of carbon monoxide, 11 methanol, 12,13 ethanol, 14,15 and...

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The Kinetics of Adsorption, Surface Reaction, and Electrochemical Oxidation of Propane on Platinum in Hydrofluoric Acid

Cited by 10 publications

References 16 publications

The Electrosorption and the Potentiodynamic Electrooxidation of Ethane on Platinum at Different Temperatures

The Electrosorption and the Potentiodynamic Electrooxidation of Ethane on Platinum at Different Temperatures

Mathematical model for a direct propane phosphoric acid fuel cell

Real-Time Mass Spectrometric Analysis of the Anode Exhaust Gases of a Direct Propane Fuel Cell

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