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Electronic states of catalysts

Examination of the electronic states of catalysts and of rare earth dopants in phosphors are other applications which come to mind. When more is known about some of the yet unexplored properties of other possible Mossbauer nuclides, Mossbauer spectroscopy bids fair to being a powerful tool in rare earth chemistry. [Pg.125]

XPS experiments to study the electronic state of catalysts were carried out on an ESCA-3 VC electron spectrometer. Vacuums in tho analyzer and preparation chambers were 1-2 10 and 5 10 Pa, respectively, XPS spectra were calibrated according to the Cis line whose binding energy was taken to be = 285.0 eV (ref. 4). [Pg.438]

Adsorbates acting as promoters usually interact strongly with the catalyst surface. The chemisorptive bond of promoters is usually rather strong and this affects both the chemical (electronic) state of the surface and quite often... [Pg.23]

As described above, XAS measurements can provide a wealth of information regarding the local structure and electronic state of the dispersed metal particles that form the active sites in low temperature fuel cell catalysts. The catalysts most widely studied using XAS have been Pt nanoparticles supported on high surface area carbon powders,2 -27,29,so,32,33,38-52 represented as Pt/C. The XAS literature related to Pt/C has been reviewed previ-ously. In this section of the review presented here, the Pt/C system will be used to illustrate the use of XAS in characterizing fuel cell catalysts. [Pg.381]

The electronic structure of a solid metal or semiconductor is described by the band theory that considers the possible energy states of delocalized electrons in the crystal lattice. An apparent difficulty for the application of band theory to solid state catalysis is that the theory describes the situation in an infinitely extended lattice whereas the catalytic process is located on an external crystal surface where the lattice ends. In attempting to develop a correlation between catalytic surface processes and the bulk electronic properties of catalysts as described by the band theory, the approach taken in the following pages will be to assume a correlation between bulk and surface electronic properties. For example, it is assumed that lack of electrons in the bulk results in empty orbitals in the surface conversely, excess electrons in the bulk should result in occupied orbitals in the surface (7). This principle gains strong support from the consistency of the description thus achieved. In the following, the principle will be applied to supported catalysts. [Pg.2]


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See also in sourсe #XX -- [ Pg.125 ]




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