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Water oxidation with molecularly defined iridium complexes: insights into Homogeneous versus Heterogeneous catalysis

Junge, Henrik and Marquet, Nicolas and Kammer, Anja and Denurra, Stefania and Bauer, Matthias and Wohlrab, Sebastian and Gärtner, Felix and Pohl, Marga-Martina and Spannenberg, Anke and Gladiali, Serafino Gabriele and Beller, Matthias (2012) Water oxidation with molecularly defined iridium complexes: insights into Homogeneous versus Heterogeneous catalysis. Chemistry: a European Journal, Vol. 18 (40), p. 12749-12758. ISSN 0947-6539. eISSN 1521-3765. Article.

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DOI: 10.1002/chem.201201472

Abstract

Molecularly defined Ir complexes and different samples of supported IrO2 nanoparticles have been tested and compared in the catalytic water oxidation with cerium ammonium nitrate (CAN) as the oxidant. By comparing the activity of nano-scaled supported IrO2 particles to the one of organometallic complexes it is shown that the overall activity of the homogeneous Ir precursors is defined by both the formation of the homogeneous active species and its conversion to IrIV-oxo nanoparticles. In the first phase of the reaction the activity is dominated by the homogeneous active species. With increasing reaction time, the influence of nano-sized Ir-oxo particles becomes more evident. Notably, the different conversion rates of the homogeneous precursor into the active species as well as the conversion into Ir-oxo nanoparticles and the different particle sizes have a significant influence on the overall activity. In addition to the homogeneous systems, IrO2@MCM-41 has also been synthesized, which contains stabilized nanoparticles of between 1 and 3 nm in size. This latter system shows a similar activity to IrCl3⋅xH2O and complexes 4 and 5. Mechanistic insights were obtained by in situ X-ray absorption spectroscopy and scanning transmission electron microscopy.

Item Type:Article
ID Code:8091
Status:Published
Refereed:Yes
Uncontrolled Keywords:Heterogeneous catalysis, homogeneous catalysis, iridium, nanoparticles, oxygen, water oxidation
Subjects:Area 03 - Scienze chimiche > CHIM/04 Chimica industriale
Divisions:001 Università di Sassari > 01-a Nuovi Dipartimenti dal 2012 > Chimica e Farmacia
Publisher:Wiley
ISSN:0947-6539
eISSN:1521-3765
Deposited On:24 Oct 2012 12:14

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