Oxidative Decomposition of Methanol on Subnanometer Palladium Clusters: The Effect of Catalyst Size and Support Composition

Size and support effects in the oxidative decomposition of methanol on amorphous alumina supported subnanometer palladium clusters were studied under realistic reaction conditions of pressure and temperature. The smaller Pd 8−12 clusters were found to promote the decomposition channel to CO and hydrogen, however with mediocre activity due to poisoning. The larger Pd 15−18 clusters preferentially produce dimethyl ether and formaldehyde, without signs of posioning. A thin titania overcoat applied on the Pd 15−18 improves the sintering-resistance of the catalyst. Accompanying density functional calculations confirm the posioning of small Pd clusters by CO.