Probing CO on a rutile TiO2(110) surface using atomic force microscopy and Kelvin probe force microscopy

Probing CO at a specific site on a metal oxide surface is essential for characterizing various applications such as CO oxidation, hydrogenation, and water-gas shift reaction. Herein, we use atomic force microscopy and Kelvin probe force microscopy to probe the CO on a rutile TiO2(110) surface. Our results indicate that CO can be manipulated along the Ti row by the repulsive lateral force of "pushing" mode. Furthermore, the joint combination of precise manipulation and the distance dependence of local contact potential difference allow us to resolve the interatomic dipole moment and charge state of CO at atomic resolution. Therefore, we found that the negatively charged CO with the dipole moment of negative pole down on the rutile TiO2(110) surface. Our results suppose that both the charge state as well as the on-surface dipole interaction are very effective for CO reaction on rutile TiO2(110) surface.