Methanol adsorption on SnO2 thin films with different morphologies

Methanol adsorption on pre-oxidized SnO2 thin films with different morphologies was studied with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy. The structure of a dense texture type SnO2 film was proved to have a main peak of the (1 1 0) phase, and that of a columnar texture type SnO2 film was proved to have main peaks of the (2 1 1) and (3 0 1) phases by XRD measurement. The exposed methanol adsorbed molecularly and dissociatively on both pre-oxidized films at room temperature, however, the dense texture type SnO2 thin film showed higher catalytic activity for dissociation and oxidation of methanol in comparison with the columnar texture type one. Furthermore, the enhancement of the reactivities for oxidation of methanol was hardly observed with the columnar texture type SnO2 film even if the surface was pre-oxidized at higher pressures. The total amount of produced active O− species on the surface of the dense texture film was larger than that on the surface of the columnar texture type film. From these results, the reactivities of SnO2 thin film for the oxidation of methanol at room temperature was suggested to depend strongly upon the amount of active oxygen species O− produced on the bridging sites of the (1 1 0) terrace surface.