Single site Fe on the (110) surface of γ-Al₂O₃: insights from a DFT study including the periodic boundary approach

Examination of the stable (110) surface of γ-alumina reveals that there are three different types of sites available to host a single Fe atom. With the carefully calibrated density functional approach (M12-L/SV), three types of Fe single sites on the (110) surface of γ-alumina have been investigated under the periodic boundary conditions. The most stable Fe replacement site on the (110) surface of γ-alumina has been found to be represented by the tri-coordinated Fe_I position with the quartet spin state. The replacement of Al by Fe atoms at the Al site leads to charge redistributions of the neighboring O atoms. However, sublayer charge distribution is less affected. A significant contribution of p orbitals of the O atoms in the surface phase to the LUMO has been found for the tri-coordinated Fe_I substitution on the (110) surface. The corresponding oxygen atoms (O_A and O_A1) have been activated due to the existence of Fe_I in their neighborhood. The loosened neighboring Al_III-O_A bonds match this activation. This activation of O suggests the existence of an important source of the reactive O during the Fe catalytic oxidation of CO processes.