Catalysis of water oxidation in acetonitrile by iridium oxide nanoparticles
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Authors: | Jonnathan C Hidalgo-Acosta Manuel A Méndez Micheál D Scanlon Heron Vrubel Véronique Amstutz Wojciech Adamiak Marcin Opallo Hubert H Girault |
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Institution: | a Laboratoire d''Electrochimie Physique et Analytique , Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne , Switzerland . Email: ; b Institute of Physical Chemistry , Polish Academy of Sciences , Kasprazaka 44/52 , 01-224 Warsaw , Poland . Email: |
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Abstract: | Water oxidation catalysed by iridium oxide nanoparticles (IrO2 NPs) in water–acetonitrile mixtures using RuIII(bpy)3]3+ as oxidant was studied as a function of the water content, the acidity of the reaction media and the catalyst concentration. It was observed that under acidic conditions (HClO4) and at high water contents (80% (v/v)) the reaction is slow, but its rate increases as the water content decreases, reaching a maximum at approximately equimolar proportions (≈25% H2O (v/v)). The results can be rationalized based on the structure of water in water–acetonitrile mixtures. At high water fractions, water is present in highly hydrogen-bonded arrangements and is less reactive. As the water content decreases, water clustering gives rise to the formation of water-rich micro-domains, and the number of bonded water molecules decreases monotonically. The results presented herein indicate that non-bonded water present in the water micro-domains is considerably more reactive towards oxygen production. Finally, long term electrolysis of water–acetonitrile mixtures containing RuII(bpy)3]2+ and IrO2 NPs in solution show that the amount of oxygen produced is constant with time demonstrating that the redox mediator is stable under these experimental conditions. |
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