Chemisorption and oxidation reactions of nickel group cluster anions with N2, O2, CO2, and N2O

Abstract

Reactions of nickel (Ni−n, n=3–10), palladium (Pd−n, n=3–8), and platinum (Pt−n, n=3–7) cluster anions are investigated in a flow tube reactor. Rate coefficients are measured for reactions with N2, O2, CO2, and N2O. Reactions with O2, CO2, and N2O have rates that are greater than 10% of the collision rate for most clusters of four atoms or larger, while N2 reactions generally exhibit much lower reaction efficiencies. All the reactions studied show a strong dependence on cluster elemental composition. Many of the palladium cluster reactions are significantly faster than the corresponding nickel and platinum cluster reactions, while Ni−n and Pt−n have similar rate coefficients. Pt−6 is observed to have anomalously low rate constants for reactions with N2, CO2, and N2O compared to neighboring platinum clusters sizes and the nickel and palladium hexamers. N2, CO2, and O2 reactions are generally association reactions with varying degrees of cluster fragmentation observed. N2O reactions result in sequential addition of O atoms to the cluster. The extent of cluster fragmentation for the various reagents can be correlated with the estimated exothermicities of the adsorption processes.