Surface Composition of Palladium Blacks of Different Methods of Preparation

The surface composition of two Pd blacks was monitored by XPS. The samples contained ∼75% Pd with carbon and oxygen impurities. The sample reduced in aqueous medium contained also Na plus K impurities (∼1% each). Their possible organic counter ions appeared in the carbon region although no quantitative agreement could be established. The possible influence of the possible surface dipoles (with the alkali pointing outwards) on selective hydrogenation processes is pointed out. This revised version was published online in June 2006 with corrections to the Cover Date.