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Metal corroles as electrocatalysts for oxygen reduction
James P Collman1, Marina Kaplun, Richard A Decréau
1Department of Chemistry, Stanford University, Stanford, CA 94305, USA. jpc@stanford.edu
Dalton Transactions (Cambridge, England : 2003)
|January 13, 2006
Summary
Metal corroles catalyze oxygen electroreduction. The specific metal ion, like cobalt or iron, dictates whether oxygen is reduced to hydrogen peroxide or water, with iron corroles showing a predominant four-electron pathway.
Area of Science:
- Electrochemistry
- Catalysis
- Coordination Chemistry
Background:
- Metal corroles are porphyrin-like macrocycles with potential catalytic applications.
- Oxygen electroreduction is a critical process in energy conversion and storage.
Purpose of the Study:
- To investigate the electrocatalytic activity of metal corroles in oxygen reduction.
- To elucidate the reaction pathways and mechanisms of oxygen electroreduction mediated by different metal corroles.
Main Methods:
- Rotating ring disk electrode (RRDE) voltammetry was employed.
- Studies were conducted in aqueous solutions across a range of pH.
- Electrochemical data were analyzed using Tafel slopes and inhibition studies.
Main Results:
- Catalysis of O2 electroreduction by metal corroles initiates at potentials significantly more positive than expected.
- Cobalt corroles selectively produce hydrogen peroxide (H2O2).
- Iron corroles exhibit parallel two- and four-electron reduction pathways, with a dominance of the four-electron process.
Conclusions:
- The electrocatalytic behavior of O2 reduction is highly dependent on the central metal ion in the corrole ligand.
- Proposed mechanisms for O2 reduction are supported by pH-dependent studies and electrochemical analysis.
- An imidazole-tailed iron corrole demonstrates catalase-like activity, catalyzing H2O2 disproportionation.