Carbon Monoxide Activation on Small Iron Magnetic Cluster Surfaces, Fe<sub><i>n</i></sub>CO, <i>n</i> = 1–20. A Theoretical Approach
Patricio Limon, Alan Miralrio, Rodolfo Gómez‐Balderas, Miguel Castro
Abstract
The chemical activation of the carbon monoxide (CO) molecule on the surface of iron clusters Fen (n = 1–20) is studied in this work. By means of density functional theory (DFT) all-electron calculations, we have found that the adsorption of CO over the bare magnetic Fen (n = 1–20) clusters is thermochemically favorable. The Fen–CO interaction increases the C–O bond length, from 1.128 ± 0.014 Å, for isolated CO, up to 1.251 Å, for Fe9CO. Also, the calculated wavenumbers associated with the stretching modes νCO are decreased, or red-shifted, as another indicator of the CO bond weakening, passing from 2099 ± 4 to 1438 cm–1. Markedly, wavenumbers of vibrational modes νCO agree admirably well in comparison with experimental results reported for FenCO (n = 1, 18–20), getting small errors below 2.6%. The C–O bond is enlarged on the FenCO (n = 1–20) composed systems, as the CO molecule increases its bonding, charge transference, and coordination with the iron cluster. Therefore, small bare iron particles Fen (n = 1–20) can be proposed to promote the CO dissociation, especially Fe9CO, which has been proven to obtain the most prominent activation of the strong C–O bond by means of the charge transference from the metal core.