Abstract
Two catalyst systems, for the ultimate use in fuel cell electrodes, have been studied with spectroscopic and general electrochemical methods. Macrocyclic metal N{sub 4}-chelates, one of these catalyst systems, are after certain preliminary preparation steps candidates for the use as electro catalysts in the cathodic reduction of dioxygen. The preliminary preparation consists in a heat-treatment that for yet unknown reasons increases the activity and stability of these catalysts. Metal N{sub 4}-macrocycles, particularly cobalt and iron tetraphenylporphyrins, in various preparation mixtures with carbon, have been heat-treated at temperatures between 300-1000 deg C. Measurements of catalytic activity have been correlated with ESCA and Moessbauer measurements. Carbon supported porphyrins undergo partial decomposition upon pyrolysis and in this process stable bonds with the carbon matrix are formed which stabilize the metal N{sub 4}-unit and facilitates electron transfer between MN{sub 4}-unit and support. The MN{sub 4}-unit remains intact in this process and is thus concluded to be the active site. Pure crystalline porphyrins polymerize upon pyrolysis with a concomitant increase in conductivity which is the reason for the increase in activity for these catalysts. The second catalytic reaction under study is the electrocatalytic reduction of methanol on platinum - a reaction that takes place at
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Citation Formats
Wideloev, A.
Fuel cell electro catalysis; A spectroscopic study.
Sweden: N. p.,
1993.
Web.
Wideloev, A.
Fuel cell electro catalysis; A spectroscopic study.
Sweden.
Wideloev, A.
1993.
"Fuel cell electro catalysis; A spectroscopic study."
Sweden.
@misc{etde_10117154,
title = {Fuel cell electro catalysis; A spectroscopic study}
author = {Wideloev, A}
abstractNote = {Two catalyst systems, for the ultimate use in fuel cell electrodes, have been studied with spectroscopic and general electrochemical methods. Macrocyclic metal N{sub 4}-chelates, one of these catalyst systems, are after certain preliminary preparation steps candidates for the use as electro catalysts in the cathodic reduction of dioxygen. The preliminary preparation consists in a heat-treatment that for yet unknown reasons increases the activity and stability of these catalysts. Metal N{sub 4}-macrocycles, particularly cobalt and iron tetraphenylporphyrins, in various preparation mixtures with carbon, have been heat-treated at temperatures between 300-1000 deg C. Measurements of catalytic activity have been correlated with ESCA and Moessbauer measurements. Carbon supported porphyrins undergo partial decomposition upon pyrolysis and in this process stable bonds with the carbon matrix are formed which stabilize the metal N{sub 4}-unit and facilitates electron transfer between MN{sub 4}-unit and support. The MN{sub 4}-unit remains intact in this process and is thus concluded to be the active site. Pure crystalline porphyrins polymerize upon pyrolysis with a concomitant increase in conductivity which is the reason for the increase in activity for these catalysts. The second catalytic reaction under study is the electrocatalytic reduction of methanol on platinum - a reaction that takes place at the anode in a methanol fuel cell. This reaction does only reach completion at potentials that are much higher than the reversible potential because of the formation of a tenaciously held reaction intermediate. ESCA and SIMS measurements have been employed to reveal the identity of this intermediate that is not yet fully known. For Pt-sheets used in methanol oxidation some CO-species can be detected, but there is an abundance of other hydrocarbons as well. 105 refs, 12 figs}
place = {Sweden}
year = {1993}
month = {Oct}
}
title = {Fuel cell electro catalysis; A spectroscopic study}
author = {Wideloev, A}
abstractNote = {Two catalyst systems, for the ultimate use in fuel cell electrodes, have been studied with spectroscopic and general electrochemical methods. Macrocyclic metal N{sub 4}-chelates, one of these catalyst systems, are after certain preliminary preparation steps candidates for the use as electro catalysts in the cathodic reduction of dioxygen. The preliminary preparation consists in a heat-treatment that for yet unknown reasons increases the activity and stability of these catalysts. Metal N{sub 4}-macrocycles, particularly cobalt and iron tetraphenylporphyrins, in various preparation mixtures with carbon, have been heat-treated at temperatures between 300-1000 deg C. Measurements of catalytic activity have been correlated with ESCA and Moessbauer measurements. Carbon supported porphyrins undergo partial decomposition upon pyrolysis and in this process stable bonds with the carbon matrix are formed which stabilize the metal N{sub 4}-unit and facilitates electron transfer between MN{sub 4}-unit and support. The MN{sub 4}-unit remains intact in this process and is thus concluded to be the active site. Pure crystalline porphyrins polymerize upon pyrolysis with a concomitant increase in conductivity which is the reason for the increase in activity for these catalysts. The second catalytic reaction under study is the electrocatalytic reduction of methanol on platinum - a reaction that takes place at the anode in a methanol fuel cell. This reaction does only reach completion at potentials that are much higher than the reversible potential because of the formation of a tenaciously held reaction intermediate. ESCA and SIMS measurements have been employed to reveal the identity of this intermediate that is not yet fully known. For Pt-sheets used in methanol oxidation some CO-species can be detected, but there is an abundance of other hydrocarbons as well. 105 refs, 12 figs}
place = {Sweden}
year = {1993}
month = {Oct}
}