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A Ru-Hbpp-Based Water-Oxidation Catalyst Anchored on Rutile TiO2

Authors

  • Laia Francàs,

    1. Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193 Barcelona (Spain), Fax: +(34) 977 920228
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  • Xavier Sala Dr.,

    1. Catalan Institute of Chemical Research (ICIQ), Av. Països Catalans 16, 43007 Tarragona (Spain), Fax: +(34) 93 5813101
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  • Jordi Benet-Buchholz Dr.,

    1. Catalan Institute of Chemical Research (ICIQ), Av. Països Catalans 16, 43007 Tarragona (Spain), Fax: +(34) 93 5813101
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  • Lluís Escriche Prof.,

    1. Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193 Barcelona (Spain), Fax: +(34) 977 920228
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  • Antoni Llobet Prof.

    1. Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193 Barcelona (Spain), Fax: +(34) 977 920228
    2. Catalan Institute of Chemical Research (ICIQ), Av. Països Catalans 16, 43007 Tarragona (Spain), Fax: +(34) 93 5813101
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  • Hbpp=3,5-bis(2-pyridyl)pyrazole.

Abstract

In support of a split: A water oxidation catalyst based on ruthenium bis-(2-pyridyl)pyrazole anchored on rutile TiO2 was prepared. The performance of this new material with regard to its capacity to catalytically oxidize water to molecular oxygen in a heterogeneous phase was evaluated.

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Two organic ligands based on bis-(2-pyridyl)pyrazole (Hbpp) functionalized with a para-methylenebenzoic acid (Hbpp-Ra) or its ester derivative (Hbpp-Re) were prepared and characterized. The ester-functionalized ligand was then used to prepare a series of related dinuclear ruthenium complexes of general formula [RuII2(L-L)(bpp-Rn)(trpy)2]m+ (L-L=μ-Cl, μ-acetato, or (H2O)2; n=e or a; trpy=2,2′:6′,2′′-terpyridine; m=2 or 3). The complexes were characterized in solution by 1D and 2D NMR spectroscopy, UV/Vis spectroscopy, and electrochemical techniques. The [RuII2(μ-Cl)(bpp-Re)(trpy)2](PF6)2 complex was further characterized in the solid state by X-ray diffraction. The complexes containing the free carboxylic acid ligand were anchored onto rutile TiO2 and treated with 0.1 M triflic acid solution to generate the homologous water-oxidation catalysts TiO2-[RuII2(H2O)2(bpp-Ra)(trpy)2]2+. This new hybrid material catalytically oxidizes water to molecular oxygen in a heterogeneous manner using CeIV as chemical oxidant. The generation of molecular oxygen is accompanied by the formation of carbon dioxide as well as some leaching of the Ru catalyst.

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