Fine tuning and orientation control of surface Cu complexes on TiO2(110) premodified with mercapto compounds: the effect of different mercapto group positions

Abstract

Three-dimensional structures of vacuum-deposited Cu species formed on TiO 2 (110) surfaces premodified with three mercaptobenzoic acid (MBA) isomers were studied using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) . We explored the possibility of fine tuning and orientation control of the surface Cu structures, including their coordination and

Premodified Surface Method to Obtain Ultra‐Highly Dispersed Metals and their 3D Structure Control on an Oxide Single‐Crystal Surface

“…Figure shows the PTRF‐XAFS spectra for Cu on the o ‐MBA‐modified TiO 2 (110) surface (Cu/ o ‐MBA/TiO 2 (110)), in addition to spectra for reference compounds . The Cu coverage was 0.42 ML.…”

“…The possibility of fine tuning and orientation control of the surface metal nanostructure was explored using different MBA isomers. Figure shows the model structure for Cu/ m ‐MBA/TiO 2 (110) determined by FEFF simulation that reproduced the observed spectra well, where the local structure around Cu was similar to that in Cu/ o ‐MBA/TiO 2 (110) (Figure (b)) . The S−Cu−O bonds had an almost linear structure (angle=176°) with the Cu−S and Cu−O bond distances at 0.219 nm and 0.185 nm, respectively.…”

“…Various metal atoms (Cu, Au, Ni and Pt) are vacuum‐deposited on TiO 2 (110) premodified with o ‐MBA to examine its effects on the dispersion of the metal atoms over the surface. The carboxylic acid group of o ‐MBA binds to TiO 2 (110) with the bridge‐bidentate form (Figure (b)), and the adsorbed o ‐MBA molecules form a densely packed monolayer according to spectroscopic ellipsometry and X‐ray photoelectron spectroscopy (XPS) measurements . Homogeneity of the deposited metal species was checked by the width and shape of the corresponding photoelectron peaks (Cu2p, Au4 f, Ni2p and Pt4 f ) in the XPS measurements.…”

“…In contrast, if the oxide support surface is premodified using an organic ligand that strongly anchors metal atoms to the surface through covalent bonds, then attachment of ultra‐highly dispersed metal species such as monatomic metal species can be expected without the need for organometallic compounds. We have successfully prepared atomically dispersed metals (single metal dispersion) with this technique on the basis of metal‐ligand bonding, simply by vacuum deposition of metal atoms onto an oxide single‐crystal surface premodified with a functional organic molecule (Figure ), and their 3D structures were precisely determined using the PTRF‐XAFS technique . For example, when ortho ‐mercaptobenzoic acid ( o ‐MBA) is used as the premodification molecule, monatomic Cu, Au and Ni atoms are energetically stabilized on the TiO 2 (110) surface by the formation of bonds with sulfur of the adsorbed o ‐MBA and the bridging oxygen in the TiO 2 lattice, whereas aggregation of the metal atoms occurs easily in the absence of o ‐MBA.…”

Portable ultrahigh-vacuum sample storage system for polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy

“…Several groups have performed XAFS measurements combined with polarizationdependent, total-reflection, and fluorescence techniques to enhance the weak intensities that result from the low concentration of supported metal nanoclusters. [1][2][3][4][5] We planned to investigate the surface-deposited massselected clusters using the polarization-dependent totalreflection fluorescence x-ray absorption fine structure spectroscopy (PTRF-XAFS) to highlight cluster-substrate interactions and size-dependence, which are expected to influence the catalytic properties of the mass-selected clusters. Such clusters, which may comprise several atoms to tens of atoms, have been studied after deposition on a surface, [6][7][8][9][10] and have been reported as very active catalysts.…”