Deposition and characterisation of vanadium oxide thin films: Linking single crystal and supported catalyst

Thin films can make a useful link between single crystal and supported vanadium oxide. The deposition of vanadium oxide thin films with physical vapour deposition techniques ensures clean and highly controllable synthesis. The resulting material is easily accessed with surface sensitive techniques. On flat TiO₂ anatase substrates, XPS–XPD and UPS indicated that the vanadia deposition was epitaxial, and fully oxidised if performed in situ. A step closer to typical industrial catalysts was achieved by sputter deposition onto sub-millimetre inert particles. In addition to surface characterisation, these model particle catalysts allow use in reactors for catalytic testing under relevant process conditions. On both silica and titania supports, sputter deposited vanadia of varying thickness proved to be equally well dispersed. Oxidative dehydrogenation (ODH) activity was higher over vanadia/titania (anatase) than over vanadia/silica, demonstrating the synergetic interaction between anatase and vanadia. Highest activity in alkane ODH was observed for vanadia a few monolayers thick, supported on titania-coated particles.