Electronic Structure of Metal (M = Au, Pt, Pd, or Ru) Bilayer Modified α-Fe2O3(0001) Surfaces

Metal modified metal oxides are promising and economical catalysts for important processes such as CO oxidation and the partial oxidation of methanol. The present work is to investigate, by density functional theory, the electronic and geometric structures of metal (M = Au, Pt, Pd, or Ru) bilayer modified alpha-Fe2O3(0001) catalysts, focusing on the synergistic effect at the interface between the metal bilayer and alpha-Fe2O3(0001) support and its connection with its catalytic activity. It is found that the synergistic effect is largely dependent on the localized electron gain, electron transfer from Fe atoms to the dz(2) orbitals of the metal bilayer, and interfacial metallic/ionic bonding. Such synergistic effect is most pronounced for alpha-Fe2O3 catalysts modified with the Pt or Ru bilayer. The Au bilayer modified alpha-Fe2O3 catalyst is the most stable due to the low structural deformation of alpha-Fe2O3 support, minimal surface Fe atom spin quenching, and long Au Fe bonds. The alpha-Fe2O3 catalyst modified with Ru bilayer displays the optimal balance of the synergistic effect and structural stability that can enhance catalytic activity.