Interaction of CO and O _\textbf2 with Supported Pt Single-Atoms on TiO _\textbf2 (110)

In view of the high activity of Pt single atoms in the low-temperature oxidation of CO, we investigate the adsorption behavior of Pt single atoms on reduced rutile TiO _2 (110) surface and their interaction with CO and O _2 molecules using scanning tunneling microscopy and density function theory calculations. Pt single atoms were prepared on the TiO _2 (110) surface at 80 K, showing their preferred adsorption sites at the oxygen vacancies. We characterized the adsorption configurations of CO and O _2 molecules separately to the TiO _2 -supported Pt single atom samples at 80 K. It is found that the Pt single atoms tend to capture one CO to form Pt-CO complexes, with the CO molecule bonding to the fivefold coordinated Ti (Ti _5 \rmc ) atom at the next nearest neighbor site. After annealing the sample from 80 K to 100 K, CO molecules may diffuse, forming another type of complexes, Pt-(CO) _2 . For O _2 adsorption, each Pt single atom may also capture one O _2 molecule, forming Pt-O _2 complexes with O _2 molecule bonding to either the nearest or the next nearest neighboring Ti _5 \rmc sites. Our study provides the single-molecule-level knowledge of the interaction of CO and O _2 with Pt single atoms, which represent the important initial states of the reaction between CO and O _2 .