Stabilizing Fe Single Atoms on Rutile-TiO₂(110) Surface Via Atomic Substitution

Stable anchoring of dispersed metal atoms through either surface adsorption or lattice substitution on support surfaces is a prerequisite for highly efficient catalytic performance. Atomic-level insights into these processes are necessary to understand the metal-support interactions. Here, we identify multiple Fe single-atom configurations on the rutile-TiO₂(110) surface using scanning tunneling microscopy (STM) and density functional theory (DFT). Our results show that an Fe atom can either adsorb on a surface O site (configuration I) or stably substitute a surface lattice Ti atom (configuration II). A transformation from configuration I to configuration II can be induced by STM manipulation. Furthermore, the substitutional Fe atom can capture an additional Fe atom to form a dual Fe-Fe complex (configuration III). DFT calculations reveal that these Fe species contribute different states in either the bandgap or the conduction band. These atomistic insights pave the way for interrogating the integrated performance of nonprecious, TiO₂-supported Fe single-atom catalysts.