title: Microsecond X-ray Absorption Spectroscopy Identification of Co(I) Intermediates in Cobaloxime-Catalyzed Hydrogen Evolution.
abstract: Rational development of efficient photocatalytic systems for hydrogen production requires understanding the catalytic mechanism and detailed information about the structure of intermediates in the catalytic cycle. We demonstrate how time-resolved X-ray absorption spectroscopy in the microsecond time range can be used to identify such intermediates and to determine their local geometric structure. This method was used to obtain the solution structure of the Co(I) intermediate of cobaloxime, which is a non-noble metal catalyst for solar hydrogen production from water. Distances between cobalt and the nearest ligands including two solvent molecules and displacement of the cobalt atom out of plane formed by the planar ligands have been determined. Combining in situ X-ray absorption and UV/Vis data, we demonstrate how slight modification of the catalyst structure can lead to the formation of a catalytically inactive Co(I) state under similar conditions. Possible deactivation mechanisms are discussed.
authors.affiliation: Paul Scherrer Institute, 5232 Villigen PSI (Switzerland). grigory.smolentsev@psi.ch.
authors.forename: Grigory
authors.initials: G
authors.lastname: Smolentsev
authors.affiliation: Laboratory of Chemistry and Biology of Metals, Univ. Grenoble Alpes, CEA, CNRS, Grenoble (France).|Department of Materials Science and Milano-Bicocca Solar Energy, Research Center, University of Milano-Bicocca, INSTM Unit, 20125 Milano (Italy).
authors.forename: Bianca
authors.initials: B
authors.lastname: Cecconi
authors.affiliation: International Research Center "Smart Materials", Southern Federal University, 344090 Rostov-on-Don (Russia).
authors.forename: Alexander
authors.initials: A
authors.lastname: Guda
authors.affiliation: Laboratory of Chemistry and Biology of Metals, Univ. Grenoble Alpes, CEA, CNRS, Grenoble (France).
authors.forename: Murielle
authors.initials: M
authors.lastname: Chavarot-Kerlidou
authors.affiliation: Paul Scherrer Institute, 5232 Villigen PSI (Switzerland).|Institute for Chemical and Bioengineering, ETH Zurich, 8093 Zurich (Switzerland).
authors.forename: Jeroen A
authors.initials: JA
authors.lastname: van Bokhoven
authors.affiliation: Paul Scherrer Institute, 5232 Villigen PSI (Switzerland).
authors.forename: Maarten
authors.initials: M
authors.lastname: Nachtegaal
authors.affiliation: Laboratory of Chemistry and Biology of Metals, Univ. Grenoble Alpes, CEA, CNRS, Grenoble (France).
authors.forename: Vincent
authors.initials: V
authors.lastname: Artero
keywords: X-ray absorption spectroscopy; XANES; photocatalysis; solar fuels; transient X-ray absorption