Stability and Reversible Oxidation of Sub‐Nanometric Cu <sub>5</sub> Metal Clusters: Integrated Experimental Study and Theoretical Modeling**
David Buceta, Shahana Huseyinova, Miguel Cuerva, Héctor J. Lozano, Lisandro J. Giovanetti, J. Lopez, Patricia López‐Caballero, Alexandre Zanchet, Alexander O. Mitrushchenkov, Andreas Hauser, Giampaolo Barone, Cristián Huck‐Iriart, Carlos Escudero, Juan Carlos Hernández‐Garrido, José J. Calvino, Miguel López‐Haro, María Pilar de Lara‐Castells, Félix G. Requejo, M. Arturo López‐Quintela
Abstract
Abstract Sub‐nanometer metal clusters have special physical and chemical properties, significantly different from those of nanoparticles. However, there is a major concern about their thermal stability and susceptibility to oxidation. In situ X‐ray Absorption spectroscopy and Near Ambient Pressure X‐ray Photoelectron spectroscopy results reveal that supported Cu 5 clusters are resistant to irreversible oxidation at least up to 773 K, even in the presence of 0.15 mbar of oxygen. These experimental findings can be formally described by a theoretical model which combines dispersion‐corrected DFT and first principles thermochemistry revealing that most of the adsorbed O 2 molecules are transformed into superoxo and peroxo species by an interplay of collective charge transfer within the network of Cu atoms and large amplitude “breathing” motions. A chemical phase diagram for Cu oxidation states of the Cu 5 ‐oxygen system is presented, clearly different from the already known bulk and nano‐structured chemistry of Cu.