Shape variations of Pd particles under oxygen adsorption

Pd particles prepared under UHV on MgO single crystals were in situ anneale d under various pressures of O-2 at high temperature, then observed ex situ in HRTEM and WBDF imaging. Annealing induces extension of the (100) faces and particle flattening. These morphology variations are reversible after r eduction in H-2. The experimental shapes are close to the equilibrium forms . After oxygen adsorption, the evolution of the particle shapes is in good agreement with the calculated shapes from thermodynamic considerations. (C) 1998 Elsevier Science B.V. All rights reserved.