Cu K-edge

Figure C2.10.5. Magnitude of the Fourier transfonn of tire /c-weighted absorjDtion fine stmcture k (/c) measured at tire Cu K edge for tire underiDotential deposition of Cu/Au(l 11) from 0.1 M KCIO +IO M HCIO +S x 10 M Cu (010 )2+10 M potassium salt of sulfate, chloride, bromide and a mixture of sulfate and chloride, for polarization of tire x-rays parallel to tire sample surface ( ) or parallel to tire surface nonnal (E (from [81]).

FIGURE 27.13 Cu K edge XANES spectra for a Cu full layer in sulfate solution at 0.2 V (SCE) in parallel (solid line) and perpendicular (dotted line) polarizations and for metallic copper (dashed line). (Erom Soldo et al., 2002, with permission from Elsevier.)... 

Figure 30. In situ measurements of the time evolution of the Cu K-edge when a platinum electrode coated with a polymeric film of poly (methylthiophene) is cathodically polarized in an aqueous solution containing 50 mM CuCl2. (From Ref. 105, with permission.)... 

Figure 6.15 Ru and Cu K-edge EXAFS spectra at 100 K with Fourier transforms and inverse transforms of the first coordination shell of Ru/Si02, Cu/Si02 and Ru-Cu/Si02 catalysts. The inverse transforms correspond to distances between 1.7 and 3.1 A (from Sinfelt et al. [39]).

Comparison of the Cu K-edge EXAFS signals for the monometallic Cu/Si02 and the bimetallic Ru-Cu/Si02 catalyst, on the other hand, provides clear evidence for the proximity of ruthenium to copper atoms in the latter. This is seen in the different shape of the measured EXAFS signal and the distorted inverse transform of the first coordination shell. Note that the intensity of the latter is weaker for the bimetallic catalyst, while the region between k=8 and k=15 A-1 has become more important, which points to the presence of a scattering atom heavier than copper in the first coordination shell. The reduced intensity in the Cu Fourier transform of the bimetallic catalyst is indicative of a lower coordination of the copper, which is characteristic of surface atoms. 

Wang and Stack (211) reported seven four-coordinate bis(phenolato)copper(H) complexes that were chemically one-electron oxidized with tris(4-bromo-phenyl)aminium hexachloroantiomonate to the corresponding EPR silent (phe-noxyl)copper(II) species. These compounds are schematically shown in Fig. 28. In a subsequent paper (212), these authors showed by Cu K-edge XAS that oxidation of the neutral species to the monocation is ligand centered with formation of (phe-noxyl)copper(II) species, in excellent agreement with similar experiments on GO. 

Figure 23. Breakdown of the combined Cu-0 and Cu—S contribution (dashed line) and the Cu-Pt contribution (dotted line) to the Fourier transform of the Cu K edge data obtained for an upd layer of Cu on Pt/C at 0.05 V vs SCE. (Note Radial coordinate/A is the same as R/k.) (Reproduced with permission from ref 72. Copyright 1993 Elsevier Sequoia S.A., Lausanne.)...

Fig. 8. Piezo-QEXAFS spectra at the Cu K-edge recorded during reduction of a Cu/ Zn0/Al203 methanol synthesis catalyst. The recording time was 50 ms/scan, and only every 40th scan is shown (51).

Fig. 13. (h) Raw QHXAFS data near the Cu k -edge obtained in situ during reduction of... 

X-ray diffraction data were obtained using Rigaku RAD-C with a copper X-ray tube in air atmosphere. X-ray absorption measurements of Cu K-edge were performed with laboratory EXAFS equipment (Technos EXAC-820). The X-ray source with a rotating Mo target and a LaBe filament was operated at 17 kV, 100 mA (EXAFS) and 20 kV 150 mA (XANES). The samples were pressed into wafers with methyl cellulose as a binder. The measurements were carried out in air atmosphere at room temperature. EXAFS Fourier transformations were carried out over the ranges of photoelectron wave vector, k, of 2.5 -10.0 A 1. 

Figure 5. Fourier transforms of Cu K-edge EXAFS of Cu-ZSM5 after (a) and before (b) deterioration, and CuO (c) as a reference.

This approach was used to examine the redox chemistry of the Cu site in galactose oxidase (41), which had been proposed to contain an unusual Cu(III) center (52). The lack of a significant Cu K-edge energy shift between the oxidized and reduced forms of the protein demonstrated that the redox chemistry was not metal-centered and implicated another redox active site. The crystal structure of the protein subsequently revealed a novel thioether composed of a cysteine and a tyro-sinate ligand of the Cu site that is likely to be involved in the redox process (53). 

Figure 7.39. XAFS CASE STUDY surface characterization of dispersed CuO catalysts on silica and alumina/silica supports. Shown are (A) EXAFS of the Cu K-edge of the catalyst calcined in air at 543 K. The thick and thin lines indicate Si/Al and Si supports, respectively (B) EXAFS of the Cu K-edge of the catalyst reduced under a H2 flow at 543 K (C) Cu K-edge XANES spectra of the calcined catalyst on (a) Si02, (b) Si02/Al203 supports, along with references of (c) Cu foil, (d) CU2O, and (e) CuO (D) XPS spectrum of the Cu 2p core level of the calcined catalyst on a Si support (E) XPS spectrum of the catalyst on a Si/Al support. Reproduced with permission from Gervasini, A. ManzoU, M. Martra, G. Ponti, A. Ravasio, N. Sordelli, L. Zaccheria, F. J. Phys. Chem. B 2006,110, 7851.

Figure 16. Cu K-edge XANES taken for laccase immobilized on grafoil substrate in pH 4 sodium citrate buffer at the indicated potentials.

Figure 17. Cu k-edge (a) XANES and (b) Afx spectra for experimental (red line) and FEFF8 calculated theoiy model based on the structure in (c). All were collected at room temperature in pH 4 citrate buffer (lOOmM) at beam line X3-B at the NSLS...

Figure 30 Cu K-edge EXAFS spectrafor (a) Cu foil, (b) CU2O, (c) CuO and (d) Cu(OH)2...

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