Adsorption of O, OH, and H2O on Pt-Based Bimetallic Clusters Alloyed with Co, Cr, and Ni

Binding energies and preferred adsorption sites of O, OH, and H 2 O to bimetallic clusters PtX, Pt 2 X, and PtX 2 (X = Pt, Co, Cr, Ni) are determined using density functional theory. The second metal element in the alloy has stronger affinity for OH than the Pt sites, and it is able to adsorb up to two OH radicals per site in oxygenated clusters. The highest binding strength of atomic oxygen is found in the hollow sites of Ni 3 and Co 3, followed by adsorption in hollow or bridge sites of Pt 2 X or PtX 2, in all cases significantly stronger than that found in Pt 3 . H 2 O adsorbs on top sites of pure and alloy clusters with much weaker energies compared with those of OH and O; however, the H 2 O binding strength in the Co, Cr, and Ni atoms is enhanced with respect to that on the Pt site, whereas the binding strength of H 2 O on the top of Pt sites of the alloy clusters is much reduced with respect to that in the pure cluster.