Model of Catalytic Reaction Center on TiO₂ Surface

Abstract

A model of catalytic reaction center on TiO₂ surface is proposed. The model cluster contains two active titanium atoms and an active oxygen atom. It is shown that the HOMO of the model consists of the atomic orbitals of active titanium and oxygen. The HOMO also contributes to the interlayer bond. This fact shows that the structure change of TiO₂ is essential to explain the catalytic behavior.
A dissociation reaction of water molecule from the model surface is examined. The reaction path is calculated and the reaction mechanism is investigated. The reaction consists of two processes. In the first step, a hydrogen atom of the water molecule dissociates and approaches an oxygen atom in the TiO₂ active center. In the second step, a dissociated hydrogen gets an electron from the HOMO of TiO₂ and approaches another titanium atom in the active center. In this process, the hydrogen atom becomes neutral from ionic state, i.e., the hydrogen atom is reduced by this reaction.