The growth, and reactivity of monolayer V 2 O 5 films supported on TiO 2 (110) produced via the oxidation of vapor-deposited vanadium were studied using X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Oxidation of vapor-deposited vanadium in 10 -7 Torr of O 2 at 600 K produced vanadia films that contained primarily V +3 , while oxidation in 10 -3 Torr at 400 K produced films that contained primarily V +5 . The reactivity of the supported vanadia layers for the oxidation of methanol to formaldehyde was studied using TPD. The activity for this reaction was found to be a function of the oxidation state of the vanadium cations in the film. AbstractThe growth, and reactivity of monolayer V 2 O 5 films supported on TiO 2 (110) produced via the oxidation of vapor-deposited vanadium were studied using X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD).Oxidation of vapor-deposited vanadium in 10 -7 Torr of O 2 at 600 K produced vanadia films that contained primarily V +3 , while oxidation in 10 -3 Torr at 400 K produced films that contained primarily V +5 . The reactivity of the supported vanadia layers for the oxidation of methanol to formaldehyde was studied using TPD. The activity for this reaction was found to be a function of the oxidation state of the vanadium cations in the film.

The reaction of methanol to formaldehyde on both V 2 O 3 and V 2 O 5 films supported on CeO 2 (111) was studied by temperature programmed desorption (TPD). Methanol was found to react on monolayer and submonolayer vanadia films to produce formaldehyde, while multilayer films were found to be inactive for this reaction. The kinetics and mechanism of the dehydrogenation of adsorbed methoxides was found to be dependent on the oxidation state of the vanadium cations in the supported vanadia layer. On films that contained V 3+ (i.e., V 2 O 3 ), adsorbed methoxy species produced via dissociative adsorption of methanol underwent dehydrogenation to formaldehyde at 600 K. In contrast, on films that contained predominantly V 5+ (i.e., V 2 O 5 ), adsorbed methoxy species underwent dehydrogenation to produce formaldehyde at 540 K. Kinetic parameters for the methoxide dehydrogenation to formaldehyde on both V 2 O 3 and V 2 O 5 films were determined from the TPD data. The TPD results also provide insight into the thermal stability of supported vanadia films and the role of adsorbed oxygen in the oxidation of methanol to formaldehyde.