0000000000374506
AUTHOR
Antonella Rossi
Chemical effect on the XPS spectra of the valence band and on O KLL and Pd MNN Auger spectra in pumice-supported catalysts
X-ray photoelectron spectra of the valence band and X-ray-excited O KLL Auger transition of pumice-supported Pd and Pt catalysts have been obtained and compared to the corresponding spectra of pumice (a naturally occurring amorphous aluminosilicate). The changes observed indicate interaction between metal and support. The valence region of the catalysts consists of three large peaks: one due to the d band of the metals and the other to the O 2p non-bonding orbitals and bonding-type orbitals formed by a mixing of the atomic orbitals (O 2p, Si 3s and Si 3p) of oxygen and silicon from the support. The intensity decrease of the component due to the bonding orbitals, observed in the catalyst spe…
The structure of pumice: An XPS and27Al MAS NMR study
In order to investigate the surface structure of pumice, an amorphous aluminosilicate, samples of pumice and of standards of silica and alumina have been studied by x-ray photoelectron spectroscopy (XPS). The effect of a mild acid leaching was also considered. The analysis of the Si 2p, Al 2p and O 1s photoelectron peaks and the Si KLL and O KLL Auger peaks indicated that pumice is formed by tetrahedral silica with some units being replaced by aluminate, AlO2−. The acid treatment decreases the alkali and the aluminate ions. X-ray photoelectron spectra of the valence band of pumices and of standards of Al2O3 and SiO2 agree with the core-level results. To support the conclusions from the XPS …
Amorphous Complexes MM (EDTA) (H2O)4 · 2H2O . LAXS and XPS Investigation of the Local Structure
Abstract The amorphous MM (EDTA)(H2O)4·2 H2O (M = Ni,Co) substances are made up of infinite chains of alternating "hydrated" and "chelated" octahedra bridged by carboxylate groups: M(H2O)4 - M(EDTA)-M(H2O)4-... . XPS enables to ascertain that the coordination of the EDTA ligand in the amorphous phase is identical to that in the crystalline phase, i.e., hexacoordination toward the M atom and two bridging groups in the Ni -Ni, Co - Co compounds.
XPS study of pumice-supported palladium and platinum catalysts
An XPS study has been performed on samples of monometallic of palladium and platinum and on bimetallic Pd-Pt catalysts supported on pumice. A negative shift of about 0.5 eV in the Pd 3d and Pt 4f binding energies of the catalysis relative to the energies of the same levels in the pure metals suggested an increase in the electron density in both metals. A quantitative XPS analysis indicated that the supported metals did not modify the surface atomic composition of pumice
Physicochemical characterization of metal hexacyanometallate–TiO2composite materials
The paper describes the synthesis and characterization of novel TiO2–metal hexacyanometallates (MHCMs) composite materials. The starting material, TiO2, was modified by addition of cobalt-hexacyanoferrate (CoHCF) or iron-hexacyanocobaltate (FeHCC) at various concentrations. The resulting composites were characterized as follows: cyclic voltammetry (CV) followed the formation of TiO2–MHCM clusters, TEM micrographs studied their morphology, XAS and XPS data indicated that MHCM bonds to TiO2 through the nitrogen atom of its –CN group and modifies the environment of Ti compared to that of pure anatase. As expected, and confirmed by UV-Vis and XP-valence band data, the electronic properties of T…