A density functional study of oxygen vacancy formation on α-Fe 2 O 3 (0001) surface and the effect of supported Au nanoparticles

We present PBE + U calculations of gold metal nanoparticles supported on the α-Fe 2 O 3 (0001) surface. We find that the periphery atoms of Au 10 particles become oxidized through the dissociation of O 2 at the metal–oxide interface. The presence of a metal particle is also shown to substantially lower the defect formation energy for surface oxygen vacancies in the oxide support, particularly when the nanoparticle is in this semi-oxidized state. The defect formation energy is found to be dependent on the distance of the vacancy from the metal particle so that the lowest defect formation energies are calculated for oxygen vacancies created at the under the gold nanoparticle. For Au 10 /α-Fe 2 O 3 (0001) creating the vacancy under the cluster requires a defect formation energy of 2.13 eV [relative to ½O 2 (g)] and this is lowered to 0.86 eV when the perimeter of the particle is oxidized. These values are significantly lower than that for the bare α-Fe 2 O 3 (0001) surface of 3.04 eV. Oxidation of the periphery of the Au cluster to form an Au 10 O 6 particle leads to even lower vacancy formation energies for the surface oxides and much lower than the energy required to abstract an O ion from the base of the cluster.