Novel Powder-Supported Size-Selected Clusters for Heterogeneous Catalysis under Realistic Reaction Conditions

Well-defined nanoparticles show promise as model catalysts in the quest for new/improved practical catalysts with tunable chemical properties. Here we demonstrate the production, chemical performance, and stability of a new class of model catalyst systems, consisting of size-selected (Pd-N) nanoclusters supported on (graphite) powders suitable for realistic, test tube reaction conditions. The catalyst powders were synthesized by cluster beam deposition onto planar surface followed by microdicing. Cluster size-dependent (N = 55 to 400) catalytic activity/selectivity was observed in the vapor phase hydrogenation of 1-pentyne. Aberration-corrected scanning transmission electron microscopy of the nanocluster catalysts before and after catalytic measurements revealed the stability of the cluster catalysts against sintering. Larger nanoclusters, e.g., Pd-400, showed superior activity, thermal stability, and (very high) selectivity over a period of hours in the reactor.