Stabilizing Fe Single Atoms on Rutile-TiO<sub>2</sub>(110) Surface\nVia Atomic Substitution

Stable\nanchoring of dispersed metal atoms through either surface\nadsorption or lattice substitution on support surfaces is a prerequisite\nfor highly efficient catalytic performance. Atomic-level insights\ninto these processes are necessary to understand the metal–support\ninteractions. Here, we identify multiple Fe single-atom configurations\non the rutile-TiO<sub>2</sub>(110) surface using scanning tunneling\nmicroscopy (STM) and density functional theory (DFT). Our results\nshow that an Fe atom can either adsorb on a surface O site (configuration\nI) or stably substitute a surface lattice Ti atom (configuration II).\nA transformation from configuration I to configuration II can be induced\nby STM manipulation. Furthermore, the substitutional Fe atom can capture\nan additional Fe atom to form a dual Fe–Fe complex (configuration\nIII). DFT calculations reveal that these Fe species contribute different\nstates in either the bandgap or the conduction band. These atomistic\ninsights pave the way for interrogating the integrated performance\nof nonprecious, TiO<sub>2</sub>-supported Fe single-atom catalysts.