Electrochemical and electrocatalytic properties of amide-linked, cofacial dimeric metalloporphyrins
As molecular electrocatalysts for the direction reduction of dioxygen to water, certain cofacial dimeric metalloporphyrins are relevant to fuel-cell technology. By studying the electrochemical properties of these and related compounds in aqueous and nonaqueous media, a better understanding of the kinetics and the mechanisms of dioxygen reduction by these unique electrocatalysts was developed. For the most-active catalyst, nonaqueous studies show that the mixed-valence Co(III)Co(II) complex has an extremely high affinity for dioxygen, bound inside the cavity of the cofacial structure. The electrochemical behavior of this catalyst, when adsorbed onto graphite and studied in an aqueous, dioxygen-free environment was re-examined. These results, taken together, suggest that the mixed-valence complex is the active form of the dioxygen reduction catalyst. Electrochemical experiments described demonstrate that certain cofacial porphyrins possessing a single electroactive center also reduce dioxygen directly to water. These results imply that an intracavity cobalt-dioxygen adduct is stabilized by a Lewis acid-type interaction with the nonelectroactive porphyrin; this allows a reductive cleavage of the O-O bond to occur, leading to water rather than hydrogen peroxide.
- Research Organization:
- Stanford Univ., CA (USA)
- OSTI ID:
- 5259825
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
FUEL CELLS
ELECTROCATALYSTS
ELECTROCHEMISTRY
COBALT COMPOUNDS
DIMERS
OXYGEN
PORPHYRINS
REDUCTION
CARBOXYLIC ACIDS
CATALYSTS
CHEMICAL REACTIONS
CHEMISTRY
DIRECT ENERGY CONVERTERS
ELECTROCHEMICAL CELLS
ELEMENTS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
300505* - Fuel Cells- Electrochemistry
Mass Transfer & Thermodynamics