Surface Oxygen Atom as a Cooperative Ligand in Pd Nanoparticle Catalysis for Selective Hydration of Nitriles to Amides in Water: Experimental and Theoretical Studies

On the basis of an insight in surface science that Pd surfaces partially covered with oxygen adatoms (Oad) show higher reactivity for water dissociation than clean Pd surfaces, we studied the effect of Oad on the activity of carbon-supported palladium metal nanoparticle catalysts (Pd/C) for the selective hydration of nitriles to amides in water. A series of Pd/C with the same Pd loading (5 wt %) and a similar particle size (5.3–6.5 nm) but with different surface coverage of Oad were prepared and characterized by various spectroscopic methods. The freshly H2-reduced Pd/C shows no catalytic activity for hydration of acetonitrile, indicating that clean Pd metal surfaces are inactive. Air exposure of this catalyst under ambient conditions results in the formation of Pd metal NPs partially covered with Oad, which act as effective and recyclable heterogeneous catalysts for selective hydration of various nitriles to the corresponding amides. Theoretical studies based on density functional theory calculations cla...