OXYGEN-VACANCY-CONTROLLED CHEMISTRY ON A METAL-OXIDE SURFACE - METHANOL DISSOCIATION AND OXIDATION ON SNO2(110)

The effect of local composition and cation coordination on the dissociation and oxidation of methanol over SnO2(110) surfaces has been investigated. The oxidation of methanol is completely selective to formaldehyde in TDS, with the conversion dependent on the surface composition. Starting with a stoichiometric surface, the conversion first increases then passes through a maximum as the surface becomes more oxygen deficient. The variation in conversion for the oxidation reaction in TDS is caused by variations in the ability of the surface to heterolytically dissociate this weak Bronsted acid. Two methoxide decomposition channels were observed, one at 450 K associated with four-coordinate Sn2+ cations at bridging oxygen vacancies, and the second at 540 K associated with lower-coordination cation sites at in-plane oxygen vacancies. The results demonstrate the importance of local surface properties in controlling the acid/base interaction of adsorbates on SnO2 surface.