Visible Light-Driven Water Oxidation by Ir Oxide Clusters Coupled to Single Cr Centers in Mesoporous Silica
- 1 August 2006
- journal article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 128 (33), 10668-10669
- https://doi.org/10.1021/ja0625632
Abstract
Visible light-induced water oxidation has been demonstrated at an Ir oxide nanocluster coupled to a single CrVI site on the pore surface of MCM-41 mesoporous silica. The photocatalytic unit was assembled by the reaction of surface CrO groups with Ir(acac)3 precursor followed by calcination at 300 °C and bond formation monitored by FT-Raman and FT-IR spectroscopy. High-resolution Z-contrast electron micrographs of the calcined material combined with energy-dispersive X-ray spot analysis confirmed the occlusion of Ir oxide nanoparticles inside the mesopores. Oxygen evolution of an aqueous suspension of the IrxOy−CrMCM-41 upon visible light irradiation of the CrVI−O ligand-to-metal charge-transfer absorption was monitored mass-spectrometrically. Comparison of the product yields for samples with low Cr content (Cr/Si ≤ 0.02) and high Cr content (Cr/Si = 0.05) indicates that only isolated Cr centers are capable of extracting electrons from Ir oxide clusters, while di- or polychromate species are not. Water oxidation at a multielectron-transfer catalyst coupled to a single metal center has not been demonstrated before. The ability to drive water oxidation with a single metal center as electron pump offers opportunities for coupling the oxygen-evolving photocatalytic unit to reducing sites in the nanoporous scaffold.Keywords
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