The structure analysis of MoOx/TiO2(110) by polarization-dependent total-reflection fluorescence X-ray absorption fine structure

The surface structure analysis of a model catalyst MoOx/TiO2(110) was for the first time performed by polarization-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) in three different directions of the crystal surface. Two samples of MoOx/TiO2(110) were prepared by an impregnation of (NH4)(6)Mo7O24. 4H(2)O using ultra high purity water and normal distilled water. The PTRF-XAFS analysis revealed that anisotropic Mo dimer species was preferentially formed on the TiO2(110) surface, with Mo-Mo bond (0.335 nm) parallel to the [1 (1) over bar 0] direction when the ultra high purity water was used as the solvent. On the other hand, the Mo oxide on the surface prepared using normal distilled water had a symmetric tetrahedral structure (MoO4) with Mo-O of 0.176 nm, which was due to the coexistence of alkaline metals at the surface. (C) 1998 Elsevier Science B.V. All rights reserved.