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Issue 24, 2014
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Water oxidation by manganese oxides formed from tetranuclear precursor complexes: the influence of phosphate on structure and activity

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Abstract

Two types of manganese oxides have been prepared by hydrolysis of tetranuclear Mn(III) complexes in the presence or absence of phosphate ions. The oxides have been characterized structurally using X-ray absorption spectroscopy and functionally by O2 evolution measurements. The structures of the oxides prepared in the absence of phosphate are dominated by di-μ-oxo bridged manganese ions that form layers with limited long-range order, consisting of edge-sharing MnO6 octahedra. The average manganese oxidation state is +3.5. The structure of these oxides is closely related to other manganese oxides reported as water oxidation catalysts. They show high oxygen evolution activity in a light-driven system containing [Ru(bpy)3]2+ and S2O82− at pH 7. In contrast, the oxides formed by hydrolysis in the presence of phosphate ions contain almost no di-μ-oxo bridged manganese ions. Instead the phosphate groups are acting as bridges between the manganese ions. The average oxidation state of manganese ions is +3. This type of oxide has much lower water oxidation activity in the light-driven system. Correlations between different structural motifs and the function as a water oxidation catalyst are discussed and the lower activity in the phosphate containing oxide is linked to the absence of protonable di-μ-oxo bridges.

Graphical abstract: Water oxidation by manganese oxides formed from tetranuclear precursor complexes: the influence of phosphate on structure and activity

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Article information


Submitted
05 Dec 2013
Accepted
28 Feb 2014
First published
28 Feb 2014

Phys. Chem. Chem. Phys., 2014,16, 11965-11975
Article type
Paper

Water oxidation by manganese oxides formed from tetranuclear precursor complexes: the influence of phosphate on structure and activity

D. Shevchenko, M. F. Anderlund, S. Styring, H. Dau, I. Zaharieva and A. Thapper, Phys. Chem. Chem. Phys., 2014, 16, 11965
DOI: 10.1039/C3CP55125C

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