TPD STUDIES OF VANADIUM-OXIDE FILMS DEPOSITED ON GOLD

Temperature-programmed desorption (TPD) can be used to study reactions on vanadium oxide films deposited onto gold foil by evaporation. Scanning electron microscopy, X-ray diffraction, laser Raman spectroscopy, and Auger electron spectroscopy reveal that these films consist of micron-sized crystallites of fully oxidized V2O5. In vacuum, molecular O2 desorbs from the films above 775 K, a temperature at which surface oxygen lost through desorption can be replaced through surface segregation of bulk oxygen. However, after activated hydrogen is adsorbed, surface oxygen can be removed at much lower temperatures as H2O. Water desorbs at 425 K without leaving surface oxygen vacancies. After the adsorption of ethanol and ethylene, CO and CO2 are the primary desorption products (peak desorption temperatures at 670-720 K) although small amounts of acetaldehyde are also observed. This behaviour is related to that found in the catalytic oxidation of ethanol.