Reactions of Neutral Platinum Clusters with N2O and CO

Abstract

The reduction of N2O in the gas phase by isolated, neutral platinum clusters, Pt(n) (n = 4-12), was investigated using mass spectrometry. The associated oxygen transfer reactions had the general formula Pt(n)O(m-1) + N2O → Pt(n)O(m) + N2 (m = 1 or 2). The rate constants k1 and k2 for the reactions in which m = 1 and 2, respectively, were ascertained and were found to be similar to one another. Unexpectedly, Pt6O was discovered to be completely unreactive with N2O under the applied experimental conditions. The reaction mechanism was elucidated on the basis of density functional theory (DFT) calculations, which indicated a reaction barrier between Pt6O + N2O and Pt6O2 + N2. The possibility of catalyzing either the reduction of N2O or the oxidation of CO using neutral Pt(n) species was also examined and the results showed that Pt(n) does not exhibit significant catalytic properties and that O and CO instead coadsorb to Pt(n). Desorption of CO2 from the coadsorbed clusters was not clearly identifiable from mass spectra. The reactivities of the platinum clusters were discussed and compared with the properties of the highly catalytically active rhodium clusters.