Coverage-dependent oxidation and reduction of vanadium supported on anatase TiO2(1 0 1)
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© 2018 Elsevier Inc. Using a multi-technical approach, we studied the oxidation of anatase TiO 2 (1 0 1)-supported vanadium (V) clusters at room temperature. We found by ex situ XPS that the highest oxidation state is +4 at sub-monolayer coverage regardless of the O 2 pressure, and STM studies revealed that the initial oxidation proceeds through oxygen-induced disintegration of V clusters into monomeric VO 2 species. By contrast, for ∼2 monolayer V coverage, a partial oxidation to V 5+ is achieved. By in situ APXPS measurements, we found that V can be maintained in the V 5+ oxidation state irrespective of the coverage; however, in the sub-monolayer range, an O 2 pressure of at least ∼1 × 10 −5 mbar is needed. Our results suggest an enhanced reducibility of V in direct contact with the TiO 2 support compared to V in the 2nd layer, which is in line with the observed optimum V 2 O 5 loading in catalytic applications just slightly below a full monolayer.
|Enheter & grupper|
Ämnesklassifikation (UKÄ) – OBLIGATORISK
|Tidskrift||Journal of Catalysis|
|Status||Published - 2018 apr 1|
|Peer review utförd||Ja|