IR spectroscopic characterization of the co-adsorption of CO and H onto cationic Cu clusters

• Published in: Physical chemistry chemical physics : PCCP Vol. 23; no. 47; pp. 26661 - 26673
• Main Authors: Lushchikova, Olga V, Szalay, Máté, Tahmasbi, Hossein, Juurlink, Ludo B. F, Meyer, Jörg, Höltzl, Tibor, Bakker, Joost M
• Format: Journal Article
• Published: 08.12.2021
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d1cp03119h

To understand elementary reaction steps in the hydrogenation of CO 2 over copper-based catalysts, we experimentally study the adsorption of CO 2 and H 2 onto cationic Cu n + clusters. For this, we react Cu n + clusters formed by laser ablation with a mixture of H 2 and CO 2 in a flow tube-type reaction channel and characterize the products formed by IR multiple-photon dissociation spectroscopy employing the IR free-electron laser FELICE. We analyze the spectra by comparing them to literature spectra of Cu n + clusters reacted with H 2 and with new spectra of Cu n + clusters reacted with CO 2 . The latter indicate that CO 2 is physisorbed in an end-on configuration when reacted with the clusters alone. Although the spectra for the co-adsorption products evidence H 2 dissociation, no signs for CO 2 activation or reduction are observed. This lack of reactivity for CO 2 is rationalized by density functional theory calculations, which indicate that CO 2 dissociation is hindered by a large reaction barrier. CO 2 reduction to formate should energetically be possible, but the lack of formate observation is attributed to kinetic hindering. To understand elementary reaction steps in the hydrogenation of CO 2 over copper-based catalysts, we experimentally study the adsorption of CO 2 and H 2 onto cationic Cu n + ( n = 4-7) clusters.