ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 46, Number 3
JKCSEZ 46(3)
June 20, 2002 

A molecular orbital analysis based on the extended Huckel calculations has been carried out to study the OH bond activation of water on the TiO₂(110) surface. H₂O binds with its axis perpendicular to the surface on top of the five-coordinate Ti⁴⁺ atom via its 3a₁ orbital. In this bonding situation, the two-coordinated bridging O^2- atom (O_b ,basic site) on TiO₂(110) is too distant from an H atom of water to form hydrogen-bonding interactions with water that facilitate O-H bond cleavage. It has been elucidated that the O-H bond is appreciably weakened when the water molecule is tilted to give a hydrogen bond with the O_b atom. This mechanism includes mutual transfer of electron density from the 3a₁ orbital of the water molecule to the Ti⁴⁺ 3d_z² orbital and from the O _b p orbitals to the LUMO 2b₁ of the adsorbed water molecule. This should result in lengthening of the O-H bond in the surface complex and the subsequent dissociation into the fragments OH and H.