Formaldehyde adsorption geometry and energies over TiO2(1 1 0) rutile surface

The adsorption modes and electronic structure of formaldehyde on TiO2(1 1 0) were investigated using the PWDFT method. The η1(O) adsorbed mode has two stable structures: perpendicular to surface plane and tilted along the [1 1 0] direction. The η1(O) tilt geometry is ∼25 kJ/mol more stable than the η1(O) straight geometry. In the case of tilted adsorption, orbital 2b2 of formaldehyde (HOMO; O2px) has considerable overlap with Ti3d states while in the case of perpendicular adsorption, orbital 5a1 (HOMO-2; O2pz) has the strongest overlap. All lower energy adsorbed formaldehyde orbitals have better Ti overlap in the straight configuration, however.