Electrocatalytic Oxygen Reduction by Iron Tetra-arylporphyrins Bearing Pendant Proton Relays

Iron(III) meso-tetra(2-carboxyphenyl)porphine chloride (1) was investigated as a soluble electrocatalyst for the oxygen reduction reaction (ORR) in acetonitrile with [H(DMF)+]OTf–. Rotating ring-disk voltammetry, spectroelectrochemistry, and independent reactions with hydrogen peroxide indicate that...

Full description

Saved in:
Bibliographic Details
Published in:Journal of the American Chemical Society 2012-03, Vol.134 (12), p.5444-5447
Main Authors: Carver, Colin T, Matson, Benjamin D, Mayer, James M
Format: Article
Language:English
Subjects:
BEARINGS
CARBOXYLIC ACIDS
CATALYSTS
CHLORIDES
ELECTROCATALYSTS
HYDROGEN PEROXIDE
IRON
ISOMERS
OXYGEN
PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
PROTONS
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Iron(III) meso-tetra(2-carboxyphenyl)porphine chloride (1) was investigated as a soluble electrocatalyst for the oxygen reduction reaction (ORR) in acetonitrile with [H(DMF)+]OTf–. Rotating ring-disk voltammetry, spectroelectrochemistry, and independent reactions with hydrogen peroxide indicate that 1 has very high selectivity for reduction of O2 to H2O, without forming significant amounts of H2O2. Cyclic voltammetric measurements at high substrate/catalyst ratios (high oxygen pressure) allowed the estimation of a turnover frequency (TOF) of 200 s–1 at −0.4 V vs Cp2Fe+/0. This is, to our knowledge, the first reported TOF for a soluble ORR electrocatalyst under kinetically controlled conditions. The 4-carboxyphenyl isomer of 1, in which the carboxylic acids point away from the iron center, is a much less selective catalyst. This comparison shows that carboxylate groups positioned to act as proton delivery relays can substantially enhance the selectivity of ORR catalysis.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja211987f