Temperature dependence of the reaction of nickel clusters with deuterium

Abstract

The kinetics of reactions of D2 with Ni9 through Ni14 are studied in a flow-tube reactor over the temperature range 133–413 K. Rate constants for the dissociative chemisorption of the first D2 molecule have been determined. Reaction probabilities are near unity for Ni10–Ni14 and are essentially independent of temperature. For Ni9, the reaction probability is about 5% between 213 and 413 K, but increases below 213 K to ∼50% at 133 K. The possibility that these reactions are mediated by a physisorbed precursor state is discussed. The increase in Ni9 reactivity below 213 K is interpreted as due to an increase in the initial trapping of the D2 molecule on the cluster’s surface.