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A Computational Study of the Mechanism of Hydrogen Evolution by Cobalt(Diimine‐Dioxime) Catalysts
Author(s) -
Bhattacharjee Anirban,
Andreiadis Eugen S.,
ChavarotKerlidou Murielle,
Fontecave Marc,
Field Martin J.,
Artero Vincent
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201301860
Subject(s) - diimine , protonation , cobalt , catalysis , chemistry , heterolysis , photochemistry , electrochemistry , hydride , electron transfer , hydrogen , inorganic chemistry , organic chemistry , electrode , ion
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 Co I complex and that H 2 was evolved in a heterolytic manner through the protonation of a Co II 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 H 2 ‐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.