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Table 6 EXAFS refinement results obtained for experimental FT(χ(k)*k3) of hydrated VxOy/SBA-15 and V2O5.

From: Structural characterization of vanadium oxide catalysts supported on nanostructured silica SBA-15 using X-ray absorption spectroscopy

 

RModel [Å]

V2O5

hydrated VxOy-SBA-15

Type

N

RModel [Å]

R[Å]

σ22]

R[Å]

σ22]

V - O

1

1.58

1.58

0.0104

1.65

0.0126

V - O

1

1.78

1.88

0.0104C

1.92

0.0126C

V - O

2

1.88

1.88C

0.0104C

1.92C

0.0126C

V - O

1

2.02

1.88C

0.0104C

1.92C

0.0126C

V - V

2

3.08

3.11

0.0047

3.08

0.0129

V - V

1

3.43

3.39

0.0047C

3.43

0.0129C

V - V

2

3.56

3.59

0.0047C

3.65

0.0129C

  1. Type and number (N) of atoms at distance R from the V atoms in a V2O5 system compared to experimental distances and XAFS disorder parameter (σ2). Parameters were obtained from refinement of a V2O5 model structure (ICSD 60767) to the experimental V K edge XAFS FT(χ(k)*k3) of hydrated VxOy/SBA-15 (10.8 wt %) and bulk V2O5(). (k range from 2.7 - 11.0 Å-1, R range 0.9 - 3.8 Å, E0 (VxOy/SBA-15) = 0.0 eV/E0 (V2O5) = 0.0, fit residual 13.4 (VxOy/SBA-15) and 6.3 (V2O5), Nind = 18, Nfree = 7) (Subscript C indicates parameters that were correlated in the refinement). Confidence limits and significance of fitting parameters are given in Table 5.