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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.