Origin of Size-Dependent Reactivity of Nickel Cluster Ions with Methanol

Abstract

Optimized structures of nickel cluster ions, Nin+ (n = 2−8), were obtained by use of the density functional method. In comparison with the reaction of a methanol molecule with Nin+ (chemisorption, demethanation and carbide formation), it is revealed that (1) the total reaction (mainly chemisorption) cross section is anti-correlated to the HOMO−LUMO gap of Nin+ and (2) the selectivity of the carbide formation against the demethanation is determined by a propensity, “d-vacancy” (the number of the d-holes per atom); the demethanation proceeds selectively on Nin+ with a d-vacancy of less than about 1.1 and the carbide formation otherwise.