  Iron oxides (FeOx) are among the most common support materials utilized in
single atom catalysis. The support is nominally Fe2O3, but strongly reductive
treatments are usually applied to activate the as-synthesized catalyst prior to
use. Here, we study Rh adsorption and incorporation on the (1-102) surface of
hematite ({\alpha}-Fe2O3), which switches from a stoichiometric (1x1)
termination to a reduced (2x1) reconstruction in reducing conditions. Rh atoms
form clusters at room temperature on both surface terminations, but Rh atoms
incorporate into the support lattice as isolated atoms upon annealing above 400
{\deg}C. Under mildly oxidizing conditions, the incorporation process is so
strongly favoured that even large Rh clusters containing hundreds of atoms
dissolve into the surface. Based on a combination of low energy ion scattering
and scanning tunnelling microscopy data, as well as density functional theory,
we conclude that the Rh atoms are stabilized in the immediate subsurface,
rather than the surface layer.
