1. [RhIII(dmbpy)2Cl2]+ as a Highly Efficient Catalyst for Visible-Light-Driven Hydrogen Production in Pure Water: Comparison with Other Rhodium Catalysts.
- Author
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Stoll, Thibaut, Gennari, Marcello, Serrano, Isabel, Fortage, Jérôme, Chauvin, Jérôme, Odobel, Fabrice, Rebarz, Mateusz, Poizat, Olivier, Sliwa, Michel, Deronzier, Alain, and Collomb, Marie‐Noëlle
- Abstract
We report a very efficient homogeneous system for the visible-light-driven hydrogen production in pure aqueous solution at room temperature. This comprises [Rh
III (dmbpy)2 Cl2 ]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, Na3 [RhI (dpm)3 Cl] and [RhIII (bpy)Cp*(H2 O)]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)2 Cl2 ]+ to [RhI (dmbpy)2 ]+ . This reduced species can react with protons to yield the hydride [RhIII (H)(dmbpy)2 (H2 O)]2+ , which is the key intermediate for the H2 production. [ABSTRACT FROM AUTHOR]- Published
- 2013
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