A Computational Study of the Mechanism of Hydrogen Evolution by Cobalt(Diimine‐Dioxime) Catalysts |
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| Authors: | Dr Anirban Bhattacharjee Dr Eugen S Andreiadis Dr Murielle Chavarot‐Kerlidou Prof Marc Fontecave Dr Martin J Field Dr Vincent Artero |
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| Institution: | 1. Dynamo Team, DYNAMOP Group, UMR 5075, Université Grenoble 1, CNRS, CEA, Institut de Biologie Structurale “Jean‐Pierre Ebel”, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1 (France);2. Laboratoire de Chimie et Biologie des Métaux, UMR 5249, Université Grenoble 1, CNRS, CEA, 17 rue des Martyrs 38054 Grenoble Cedex 9 (France);3. Collège de France, 11 place Marcellin‐Berthelot, 75005 Paris (France) |
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| Abstract: | Cobalt(diimine‐dioxime) complexes catalyze hydrogen evolution with low overpotentials and remarkable stability. In this study, DFT calculations were used to investigate their catalytic mechanism, to demonstrate that the initial active state was a CoI complex and that H2 was evolved in a heterolytic manner through the protonation of a CoII? hydride intermediate. In addition, these catalysts were shown to adjust their electrocatalytic potential for hydrogen evolution to the pH value of the solution and such a property was assigned to the presence of a H+‐exchange site on the oxime bridge. It was possible to establish that protonation of the bridge was directly involved in the H2‐evolution mechanism through proton‐coupled electron‐transfer steps. A consistent mechanistic scheme is proposed that fits the experimentally determined electrocatalytic and electrochemical potentials of cobalt(diimine‐dioxime) complexes and reproduces the observed positive shift of the electrocatalytic potential with increasing acidity of the proton source. |
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| Keywords: | bridging ligands cobalt density functional calculations hydrogen evolution proton coupled electron transfer |
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