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The structures of Ni clusters formed on a highly-stepped TiO2(110) surface were studied by polarization-dependent total reflection fluorescence X-ray absorption fine structure analysis. When 0.8 monolayers of Ni were deposited, three-dimensional Ni clusters with 1-2 nm diameters and heights less than 1 nm were formed. Conversely, when 0.07 monolayers of Ni were deposited, an anisotropic Ni trimer with a Ni-Ni distance of 0.260 nm was created at the [001] step. We revealed that the surface modification to enhance the metal-anion interaction can control the deposited metal structure. (C) 2013 Elsevier B.V. All rights reserved.

Preparing highly dispersed monoatomic Cu species on a TiO 2 (1 1 0) surface was successfully achieved on a TiO 2 (1 1 0) surface that had been precovered with an acetic anhydride layer. Polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) spectra indicated that the three-dimensional structures of the monoatomic Cu species were stabilized on the surface by two 0.196-nm-long C–O bonds, namely, Cu–O (acetate) and Cu–O (bridging surface oxygen) bonds. The Cu species diffusion was effectively blocked by the acetate species with its molecular plane perpendicular to the [0 0 1] diffusion direction created by the dissociative adsorption of acetic anhydride.

Highly dispersed monoatomic Cu species on a TiO 2 (1 1 0) surface were successfully prepared by a new method in which the TiO 2 (1 1 0) surface was premodified with a 3-thiophenecarboxylic layer. Polarization-dependent total reflection fluorescence-X-ray absorption fine structure (PTRF-XAFS) showed the three dimensional structure of the monoatomic Cu species which were stabilized on the surface through the formation of Cu–S (adsorbate) and Cu–O (bridging oxygen) bonds.

The structure of low coverage Ni atoms on the TiO2(1 1 0) surface was studied using polarization dependent EXAFS. We found that Ni atoms interacted with oxygen atoms at the 〈 1 1 ¯ n 〉 step edges, where atomically dispersed Ni species were found with Ni–O distances at 0.199 ± 0.002 and 0.204 ± 0.003 nm in parallel and perpendicular directions to the TiO2(1 1 0) surface, respectively. The location corresponded to the virtual Ti site if the next TiO2 layer was created on the topmost TiO2 surface. The Ni location was mainly determined by the dangling bond directions of the surface oxygen atoms.

The geometrical structure of a low coverage Ni species on an α-Al 2 O 3 (0 0 0 1) single crystal surface has been studied using a polarization-dependent total reflection fluorescence extended X-ray absorption fine structure (PTRF-EXAFS) spectroscopy to reveal the bonding feature between the metal and the oxide surface. The Ni species on the α-Al 2 O 3 (0 0 0 1) surface is atomically dispersed with a Ni–O distance at 0.198 ± 0.003 nm. The adsorption site is determined to be a threefold oxygen site on top of a deep Al atom accompanied with a relaxation of the nearest neighbor oxygen atoms.

We have carried out the three-dimensional structure analysis for Mo oxides on TiO 2 (110) using total-reflection fluorescence EXAFS (extended X-ray absorption fine structure) in three different directions of the polarized vector of the incident X-rays parallel to the [110], [001] and [110] directions of the TiO 2 (110) plane. It is concluded that the Mo dimer species are selectively formed on the surface, with the Mo–Mo bond (0.335 nm) parallel to the [110] direction and also with Mo–Ti (0.296 nm) and Mo–O (0.220 nm) interfacial bonds.