Surface Reconstruction-Induced Photocatalytic Methanol Reduction Reaction on a Rutile TiO(001) Surface.

Photochemistry of methanol on TiO surfaces is of great importance both fundamentally and industrially. Methanol was previously reported only to occur photogenerated hole-participating oxidation reactions on TiO surfaces. Herein, we report that, upon UV light illumination, the methoxy species formed by methanol dissociation at the 5-fold coordinated Ti sites (CHO(a)) of a reconstructed rutile TiO(001)-(1 × 1) surface also undergoes the C-O bond cleavage into methyl fragments mediated by photogenerated electrons, in addition to the well-established photogenerated hole-participating oxidation reactions. Upon subsequent heating, the resulting methyl species undergoes hydrogenation and coupling reactions into methane and ethane, respectively. Accompanying theoretical calculations showed that the lowest unoccupied molecular orbital (LUMO) of CHO(a) is localized almost at the conduction band minimum of the CHO-adsorbed reconstructed rutile TiO(001)-(1 × 1) surface, indicating the likely TiO → CHO(a) interfacial photoexcited-electron transfer. These results greatly broaden the photochemistry of methanol on TiO surfaces and demonstrate a photocatalytic methanol-to-hydrocarbon reaction route.