Direct Imaging of Pt Single Atoms Adsorbed on TiO₂ (110) Surfaces

Noble metal nanoparticles (e.g., gold and platinum) supported on TiO₂ surfaces are utilized in many technological applications such as heterogeneous catalysts. To fully understand their enhanced catalytic activity, it is essential to unravel the interfacial interaction between the metal atoms and TiO₂ surfaces at the level of atomic dimensions. However, it has been extremely difficult to directly characterize the atomic-scale structures that result when individual metal atoms are adsorbed on the TiO₂ surfaces. Here, we show direct atomic-resolution images of individual Pt atoms adsorbed on TiO₂ (110) surfaces using aberration-corrected scanning transmission electron microscopy. Subangstrom spatial resolution enables us to identify five different Pt atom adsorption sites on the TiO₂ (110) surface. Combining this with systematic density functional theory calculations reveals that the most favorable Pt adsorption sites are on vacancy sites of basal oxygen atoms that are located in subsurface positions relative to the top surface bridging oxygen atoms