Three-Dimensional Structure Analyses of Cu Species Dispersed on TiO2(110) Surfaces Studied by Polarization-Dependent Total-Reflection Fluorescence X-ray Absorption Fine Structure (PTRF-XAFS)

Three-dimensional analysis of structures for dispersed Cu species on a TiO 2 (110) surface has been performed by a polarization-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) technique.The dispersed Cu species were prepared by a chemical reaction between Cu(DPM) 2 and a TiO 2 (110) surface and reduced with H 2 . The Cu(DPM) 2 dissociatively adsorbed on the 2-fold site of bridging oxygen atoms of the TiO 2 (110) surface to form a Cu(DPM)(O-) 2 species. Subsequent reduction of the Cu species with H 2 at 363 K produced Cu 3 trimers that were bound to the bridging oxygen atoms with the trimer plane inclined at about 30° from the TiO 2 (110) normal. There were direct Cu-O bonds at the Cu 3 trimer/TiO 2 (110) interface in addition to Cu-Cu bonds. Further reduction at 473 K produced three-dimensional prismatic small Cu 6 clusters by vertical growth in the [110] direction of the Cu fcc lattice. Orientations of the Cup 3 triangle and Cu 6 prism clusters may be regulated by the interaction between the Cu atoms and the bridging oxygen atoms on the anisotropic TiO 2 (110) surface.