Oxygen Reduction Reaction Promoted by Manganese Porphyrins

The oxygen reduction reaction (ORR) is catalyzed by manganese­(II) porphyrins in the presence of Brønsted acids (HAs). Analyses of the catalytic cyclic voltammetric profiles have permitted the ORR mechanism to be constructed and rate constants to be extracted for both the formation of the initial ox...

Full description

Saved in:
Bibliographic Details
Published in:ACS catalysis 2018-09, Vol.8 (9), p.8671-8679
Main Authors: Passard, Guillaume, Dogutan, Dilek K, Qiu, Mengting, Costentin, Cyrille, Nocera, Daniel G
Format: Article
Language:English
Subjects:
Chemistry
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:The oxygen reduction reaction (ORR) is catalyzed by manganese­(II) porphyrins in the presence of Brønsted acids (HAs). Analyses of the catalytic cyclic voltammetric profiles have permitted the ORR mechanism to be constructed and rate constants to be extracted for both the formation of the initial oxygen adduct and the O–O bond cleavage event for a series of HAs. The dependence of the formation rate constant of the oxygen adduct on reactant concentrations reveals a rate law that is first order in Mn porphyrin and oxygen substrate. A second order dependence in HA is observed for unadorned Mn porphyrin platforms whereas with Mn hangman porphyrin, a proton is provided intramolecular to the oxygen adduct and consequently the HA order is reduced to unity. The stabilization of the oxygen adduct with an additional hydrogen bond from HA engenders a rate-determining step involving O–O bond cleavage, resulting in the rare instance where the activation of the O–O bond is directly observed.
ISSN:2155-5435
2155-5435
DOI:10.1021/acscatal.8b01944