Preda Gloria, Pacchioni Gianfranco, Chiesa Mario, Giamello Elio
Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, 53-20125, Milano, Italy.
Phys Chem Chem Phys. 2009 Oct 1;11(37):8156-64. doi: 10.1039/b906192d. Epub 2009 Jun 22.
In this combined quantum chemical and EPR study we have investigated the formation of CO(2)(-) radicals by contact of CO(2) molecules with a K precovered MgO surface. K atoms have been deposited on polycrystalline MgO samples, and then exposed to CO(2). The typical EPR signal of the isolated K atoms disappears when the reaction with CO(2) takes place and a new paramagnetic species attributed to CO(2)(-) is observed. DFT cluster model calculations show that there is a spontaneous electron transfer from the adsorbed K atom to the CO(2) molecule, with formation of K(+)CO(2)(-) surface complexes. These species have the same electronic characteristics and spin distribution of gas-phase M(+)CO(2)(-) (M = Li, Na, K) molecules, but are stabilized by the presence of the ionic surface. The most stable MgO sites where the adsorption of CO(2) occurs and the computed EPR properties are discussed.
