Adsorption of Electropositive Atoms with an Odd Number of Electrons (H, K, Au) on a Perfect TiO2(110) Surface

The adsorption of electropositive atoms with an odd number of electrons (H, K, Au) on a perfect $TiO2(110)$ rutile surface is investigated using periodic DFT calculations (VASP code). The rutile surface, a closed shell system when uncovered, becomes an open‐shell system when covered by one of these adsorbates. One possibility for adsorption is to transfer electrons from the adsorbate A⋅ to the rutile‐surface, (the rutile is reduced): $A⋅→A++e−.$ The cationic $A+$ moiety will then adsorb on basic $O2−$ surface sites forming OA groups. This is the best adsorption mode for H, K and Au. Another solution is to couple two adsorbates A to give $A+$ and $A−:$ $2A⋅→A+$ and $A−$ and subsequent adsorption on basic and acidic surface sites respectively regenerating the closed‐shell system. This is the best adsorption mode for the coadsorption of Au with H or K. Then, $Au−$ adsorbs on the surface acidic site, $Ti+4,$ while $H+$ (or $K+$⁠) does on the surface basic sites, $O−2.$ Our results confirm that K coadsorption should have a significant effect on the binding of Au particles on $TiO2$ surfaces and hence on the growth.