The adsorption of CO on transition metal clusters: A case study of cluster surface chemistry

We present a discussion of recent experimental studies on the interaction of single CO molecules with transition metal clusters in the gas-phase, typically in the size range of 3 to more than 20 atoms, emphasizing specifically the insights gained from vibrational spectroscopy. Trends across the transition metals (TM) for molecular vs. dissociative chemisorption as well as for adsorption geometries are discussed and compared with the behaviour of CO adsorbed on extended surfaces. The dependence of the frequency of the internal CO stretch vibration on the size and charge of the cluster enables one to gauge quantitatively the effects of charge transfer between deposited nanoparticles and the substrate as well as of electron transfer due to the binding of co-adsorbed species.