Catalytic Oxidation of Carbon Monoxide on Monodispersed Platinum Clusters:  Each Atom Counts

Nanoclusters open fascinating opportunities for quantum engineering because quantum-size effects become dominant in determining catalytic,1-3 optical,4 electronic,5 and magnetic6 properties. We succeeded in the controlled production of low-energy and high-flux monodispersed cluster beams, which allow for a systematic study of their reactivity after deposition onto a chemically inert substrate. We investigated the catalytic reaction that is the oxidation of CO on platinum and observed a distinct atom by atom size dependency for monodispersed platinum clusters on thin MgO(100) films. These results clearly show that the efficiency of a heterogeneous catalytic reaction can be tuned by the judicious choice of particle size.