Extended X-ray Absorption Fine Structure Studies on the Structure of the Poly(vinylpyrrolidone)-Stabilized Cu/Pd Nanoclusters Colloidally Dispersed in Solution

Polymer-protected Cu/Pd bimetallic nanoclusters colloidally dispersed in a glycol solution were investigated by means of extended X-ray absorption fine structure (EXAFS). Cu/Pd alloy structures were observed in a wide range of Cu/Pd composition. Shorter Cu−Pd bond distances and more coordination numbers of Cu around Pd and Pd around Cu were found for the nanoclusters with Cu/Pd = 4:1, 3:2, and 1:1 than those expected in random alloy structures, indicating stronger interaction between Cu and Pd atoms. We proposed a “heterobond-philic” model for a new type of bimetallic nanoclusters. The preferential formation of the Cu−Pd bond may be the origin for the unique catalytic properties for hydration and hydrogenation reactions.