Oxygen desorption from alpha-Al2O3(0001) supported Rh, Pt and Pd particles

Temperature-programmed desorption (TPD) was used to study the interaction of oxygen with both large (similar to 10 nm) and small (< 2 nm) Rh, Pt and Pd particles supported on alpha-AL(2)O(3)(0001). The results of this study indicate that O-2 desorption from large particles of Rh, Pt and Pd is similar to that from low-index planes of the respective metal single crystals. Additionally, O-2 desorption from small Rh particles is similar to that from the close-packed planes of bulk Ph. In contrast. O-2 desorption from small particles of Pt and Pd occurs at a significantly higher temperature than that from the respective, low-index single crystal surfaces despite a much higher saturation oxygen coverage on the small particles. Possible explanations for the differences in O-2 desorption as a function of particle size for the various metals is discussed. (C) 1997 Elsevier Science B.V.