Cobalt-oxo core of a water-oxidizing catalyst film.
In photosynthesis, water is oxidized at a protein-bound Mn(4)Ca complex. Artificial water-oxidation catalysts that are similarly efficient and based on inexpensive and abundant materials are of great interest. Recently, assembly of a catalyst as an amorphous layer on inert cathodes by electrodeposition starting from an aqueous solution of cobalt ions and potassium phosphate has been reported. X-ray absorption spectroscopy on the cobalt catalyst film (CoCF) suggests that its central structural unit is a cluster of interconnected complete or incomplete Co(III)-oxo cubanes. Potassium ligation to Co-bridging oxygens could result in Co(3)K(mu-O)(4) cubanes, in analogy to the Mn(3)Ca(mu-O)(4) cubane motif proposed for the photosynthetic Mn complex. The similarities in function and oxidative self-assembly of CoCF and the catalytic Mn complex in photosynthesis are striking. Our study establishes a close analogy also with respect to the metal-oxo core of the catalyst.
Freie Universität Berlin, FB Physik, Arminallee 14, 14195 Berlin, Germany.
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Risch
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Khare
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Zaharieva
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Gerencser
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Chernev
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Dau
D003035:Cobalt / Q000737:chemistry*; D055664:Electrochemical Techniques / Q000379:methods; D005583:Fourier Analysis; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D014867:Water / Q000737:chemistry*
D010087:Oxides; D045332:Photosystem II Protein Complex; D014867:Water; D003035:Cobalt; C060728:cobalt oxide