CO adsorption on transition metal clusters: Trends from density functional
theory
Surf. Sci., 602 (10):
1858--1862 (May 2008)DOI: 10.1016/j.susc.2008.03.024
Abstract
This work reports for the first time the trends for carbon monoxide
(CO) chemisorption on transition metal clusters present in supported
metal catalysts. In particular, the energetic, structural and infrared
adsorption characteristics of linearly (atop) CO adsorbed on transition
metal nano-clusters of less than 10 A in size were explored. Spin-unrestricted
density functional theory (DFT) calculations were employed to explore
the trends of CO adsorption energy (A(M-CO)) and C-O vibrational
frequency (v(CO)) for clusters composed of Ni, Cu, Ru, Rh, Pd,
Ag, It, Pt and Au. The effects of the transition metal electronic
structure onto the adsorption energy of CO and the vibrational
stretching frequency of C-O, and how these chemical parameters
can be correlated to the catalytic activity of transition supported
metal catalysts that involve the adsorption, surface diffusion, and
C-O bond dissociation elementary steps in heterogeneous catalytic
surface reactions, are discussed. Our findings show that an increase
of the electronic d-shell occupancy and the principal quantum number
(n) in transition metals causes an increase in the vibrational stretching
frequency of the C-O bond. This trend is inconsistent with the
classical Blyholder model for the metal-carbonyl bond. (C) 2008
Elsevier B.V. All rights reserved.