[RhIII(dmbpy)2Cl2]+ as a Highly Efficient Catalyst for Visible‐Light‐Driven Hydrogen Production in Pure Water: Comparison with Other Rhodium Catalysts |
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Authors: | Thibaut Stoll Dr Marcello Gennari Dr Isabel Serrano Dr Jérôme Fortage Dr Jérôme Chauvin Dr Fabrice Odobel Dr Mateusz Rebarz Dr Olivier Poizat Dr Michel Sliwa Dr Alain Deronzier Dr Marie‐Noëlle Collomb |
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Institution: | 1. Université Joseph Fourier Grenoble 1/CNRS, Département de Chimie Moléculaire, UMR 5250, Institut de Chimie Moléculaire de Grenoble, FR‐CNRS‐2607, Laboratoire de Chimie Inorganique Rédox, BP 53, 38041 Grenoble Cedex 9 (France), Fax: (+33)?4‐76‐51‐42‐67;2. CEISAM, UMR 6230, Université de Nantes, CNRS, 2 rue de la Houssinière, 44322 Nantes Cedex 3 (France);3. Laboratoire de Spectrochimie Infrarouge et Raman, UMR 8516 CNRS‐Université Lille 1 Sciences et Technologies, 59655 Villeneuve d'Ascq Cedex (France) |
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Abstract: | We report a very efficient homogeneous system for the visible‐light‐driven hydrogen production in pure aqueous solution at room temperature. This comprises RhIII(dmbpy)2Cl2]Cl ( 1 ) as catalyst, Ru(bpy)3]Cl2 ( PS1 ) as photosensitizer, and ascorbate as sacrificial electron donor. Comparative studies in aqueous solutions also performed with other known rhodium catalysts, or with an iridium photosensitizer, show that 1) the PS1 / 1 /ascorbate/ascorbic acid system is by far the most active rhodium‐based homogeneous photocatalytic system for hydrogen production in a purely aqueous medium when compared to the previously reported rhodium catalysts, Na3RhI(dpm)3Cl] and RhIII(bpy)Cp*(H2O)]SO4 and 2) the system is less efficient when IrIII(ppy)2(bpy)]Cl ( PS2 ) is used as photosensitizer. Because catalyst 1 is the most efficient rhodium‐based H2‐evolving catalyst in water, the performance limits of this complex were further investigated by varying the PS1 / 1 ratio at pH 4.0. Under optimal conditions, the system gives up to 1010 turnovers versus the catalyst with an initial turnover frequency as high as 857 TON h?1. Nanosecond transient absorption spectroscopy measurements show that the initial step of the photocatalytic H2‐evolution mechanism is a reductive quenching of the PS1 excited state by ascorbate, leading to the reduced form of PS1 , which is then able to reduce RhIII(dmbpy)2Cl2]+ to RhI(dmbpy)2]+. This reduced species can react with protons to yield the hydride RhIII(H)(dmbpy)2(H2O)]2+, which is the key intermediate for the H2 production. |
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Keywords: | homogeneous catalysis hydrogen photocatalysis rhodium water chemistry |
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