Local Structure and Coordination Define Adsorption in a Model Ir1/Fe3O4 Single‐Atom Catalyst. (19th August 2019) - Jakub, Zdenek
Abstract: Single‐atom catalysts (SACs) bridge homo‐ and heterogeneous catalysis because the active site is a metal atom coordinated to surface ligands. The local binding environment of the atom should thus strongly influence how reactants adsorb. Now, atomically resolved scanning‐probe microscopy, X‐ray photoelectron spectroscopy, temperature‐programmed desorption, and DFT are used to study how CO binds at different Ir1 sites on a precisely defined Fe3 O4 (001) support. The two‐ and five‐fold‐coordinated Ir adatoms bind CO more strongly than metallic Ir, and adopt structures consistent with square‐planar Ir I and octahedral Ir III complexes, respectively. Ir incorporates into the subsurface already at 450 K, becoming inactive for adsorption. Above 900 K, the Ir adatoms agglomerate to form nanoparticles encapsulated by iron oxide. These results demonstrate the link between SAC systems and coordination complexes, and that incorporation into the support is an important deactivation mechanism. Abstract : Die Koordination eines einzelnen Atoms auf einem Oxidträger hat drastische Auswirkungen auf dessen Fähigkeit zur Adsorption von Kohlenmonoxid. Die beobachteten Effekte können mit einfachen Argumenten aus der Koordinationschemie erklärt werden, was die Hypothese bestätigt, dass Einzelatomkatalysatoren viel mit metallorganischen Komplexen, wie sie in der homogenen Katalyse verwendet werden, gemeinsam haben.