Insights into the mechanism of photosynthetic H 2 evolution catalyzed by a heptacoordinate cobalt complex

Lucarini, Fiorella; Fize, Jennifer; Morozan, Adina; Marazzi, Marco; Natali, Mirco; Pastore, Mariachiara; Artero, Vincent; Ruggi, Albert

doi:10.1039/C9SE00434C

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Insights into the mechanism of photosynthetic H 2 evolution catalyzed by a heptacoordinate cobalt complex

Lucarini, Fiorella Université de Fribourg - Département de Chimie - 1700 Fribourg - Switzerland
Fize, Jennifer Univ. Grenoble Alpes - CNRS - CEA - IRIG - Laboratoire de Chimie et Biologie des Métaux
Morozan, Adina Univ. Grenoble Alpes - CNRS - CEA - IRIG - Laboratoire de Chimie et Biologie des Métaux
Marazzi, Marco Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering - Universidad de Alcalá - E-28805 Alcalá de Henares (Madrid) - Spain - Chemical Research Institute “Andrés M. del Río” (IQAR)
Natali, Mirco Università degli studi di Ferrara - Dipartimento di Scienze Chimiche e Farmaceutiche - 44121 Ferrara - Italy
Pastore, Mariachiara Université de Lorraine & CNRS - Laboratoire de Physique et Chimie Théoriques (LPCT) - Nancy - France
Artero, Vincent Univ. Grenoble Alpes - CNRS - CEA - IRIG - Laboratoire de Chimie et Biologie des Métaux
Ruggi, Albert Université de Fribourg - Département de Chimie - 1700 Fribourg - Switzerland

26.11.2019

Published in:

Sustainable Energy & Fuels. - 2020, vol. 4, no. 2, p. 589–599

English H2 evolution catalyzed by a heptacoordinate complex under both electro- (1) and photo-chemical (2) conditions is analyzed in detail in order to gain insights into the mechanism of the processes. The complex shows high catalytic activity for hydrogen production in acetonitrile, in the presence of trifluoroacetic acid and triethylammonium tetrafluoroborate as proton sources. Foot-of-the-wave analysis (FOWA) and Tafel plot analysis have been applied to elucidate the kinetics of the hydrogen evolution mechanism and to benchmark the catalytic performances, respectively, with remarkably high rates being obtained at the expense of high overpotentials. Transient absorption spectroscopy measurements have been performed to characterize the kinetics and relevant intermediates formed under photocatalytic conditions. A computational investigation, based on density functional theory (DFT) and time- dependent DFT (TD-DFT), has also been carried out to characterize the intermediate species and support the experimental results. A combination of both experimental and theoretical data suggests the formation of catalytic intermediates displaying dangling pyridine groups in both the one- and two-electron reduced species, possibly acting as proton-transfer relays to enable efficient H–H bond formation.

Faculty

Faculté des sciences et de médecine

Department

Département de Chimie

Language