title: Water oxidation catalysis by Co(II) impurities in Co(III)4O4 cubanes.
abstract: The observed water oxidation activity of the compound class Co4O4(OAc)4(Py-X)4 emanates from a Co(II) impurity. This impurity is oxidized to produce the well-known Co-OEC heterogeneous cobaltate catalyst, which is an active water oxidation catalyst. We present results from electron paramagnetic resonance spectroscopy, nuclear magnetic resonance line broadening analysis, and electrochemical titrations to establish the existence of the Co(II) impurity as the major source of water oxidation activity that has been reported for Co4O4 molecular cubanes. Differential electrochemical mass spectrometry is used to characterize the fate of glassy carbon at water oxidizing potentials and demonstrate that such electrode materials should be used with caution for the study of water oxidation catalysis.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Ullman
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.forename: Michael
authors.initials: M
authors.lastname: Huynh
authors.forename: D Kwabena
authors.initials: DK
authors.lastname: Bediako
authors.forename: Hongsen
authors.initials: H
authors.lastname: Wang
authors.forename: Bryce L
authors.initials: BL
authors.lastname: Anderson
authors.forename: David C
authors.initials: DC
authors.lastname: Powers
authors.forename: John J
authors.initials: JJ
authors.lastname: Breen
authors.forename: Héctor D
authors.initials: HD
authors.lastname: Abruña
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Nocera
mesh_terms: D002384:Catalysis; D002623:Chemistry Techniques, Analytical; D003035:Cobalt / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011786:Quality Control; D014867:Water / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D014867:Water; D003035:Cobalt