Ice-assisted preparation of silica-supported vanadium oxide particles

Sökning: WFRF:(Kaya D) > Ice-assisted prepar...

QC 20111205
Vanadium oxide particles were prepared by physical vapor deposition of vanadium in oxygen ambient onto ice-precovered well-ordered silica thin films. Morphology, electronic structure, and vibrational properties of the vanadia deposits were studied by scanning tunneling microscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and infrared reflection absorption spectroscopy. The results show that the ice behaves as an oxidative agent, that favors vanadium oxidation up to V4+, and as a buffer layer that precludes strong interaction of the V adatoms with the silica film. At room temperature, upon desorption of the unreacted water, nanosized particles of vanadia hydroxide-like gel, containing V-OH and, to a lesser extent, vanadyl (VO) species, are formed. Vacuum annealing at 550 K leads to the total dehydration and partial reduction of the particles to V2O3, which expose the V-terminated surface. Subsequent reoxidation in 10(-6) mbar of O-2 irreversibly transforms the surface to the VO terminated, that is, the same as for the reactive deposition onto the clean silica surface. The results suggest that the structure of silica-supported vanadia catalysts is determined by a calcination step and should be considered under low oxygen pressure conditions as vanadium sesquioxide nanoparticles with the VO terminated surface.

Sun, Y. -N (författare)
Weissenrieder, JonasFritz Haber Institute,Chemical Physics(Swepub:kth)u1dg6qtm (författare)
Stacchiola, D. (författare)
Shaikhutdinov, S. (författare)
Freund, H. -J (författare)
Fritz Haber InstituteChemical Physics (creator_code:org_t)

Ingår i:The Journal of Physical Chemistry C: American Chemical Society (ACS)111:14, s. 5337-53441932-74471932-7455

Av författaren/redakt...: Kaya, S.; Sun, Y. -N; Weissenrieder, J ...; Stacchiola, D.; Shaikhutdinov, S ...; Freund, H. -J

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