Fe K-edge XANES

EXAFS cannot be used to distinguish between [Fe(CN)6] and [Fe(CN)6] because the difference in Fe - C and Fe- N distances is within experimental error. Simulation of the Fe K-edge XANES absorption edge indicates, how-... 

Figure 3.38 (A) In situ Fe K-edge XANES of FePc KB in 0.5 M H2S04 at 0.4 V (a, dashed line), 0.84 V (b, solid line), and 0.08 V (c, dotted line). (B) Same as (A) in an expanded scale. Insert cyclic voltam-mogramofFePc/KB recorded at 10 mV s-1 in 0.5 M H2S04,wherea,b and c indicate the potentials at which XANES spectra were recorded.

Figure 3.79 Fe K-edge XANES of FeTMPPCl BP pyrolyzed at 800°C in powder form (solid line) and following incorporation into a Teflon-bonded electrode immersed in 0.1 M H3PO4 at open circuit (about 0.6 V versus DHE, in situ, dotted line). Also shown in this figure is the ex situ XANES of an Fe foil for comparison (dashed line).

Perhaps the most significant information regarding the redox properties ofpyrolyzed macrocycles has been obtained from in situ Fe K-edge XANES measurements for... 

Figure 3.82 Series of in situ Fe K-edge XANES for intact (A) and heat treated FeTMPPCI BP (B) as a function of the applied potential in 0.1 M H3PO4. The arrows point in the direction of increasing potentials for data collected at -0.20, 0.00, 0.20, 0.30, 0.50, 0.60, 0.80, 0.90 and 1.15 V versus DHE.

Figure 3.83 Comparison between the in situ Fe K-edge XANES of FeTMPPCI BP before (dotted line) and after (solid line) heat treatment at —0.20 (A) and 0.90V (B) based on the data in Figure 3.82.

Fig. 12. Calculated Fe K-edge XANES for an Fe(CN)e cluster (Rpe-c = >903 A, Rc-n = 1-134 A) with both C and N shells included (solid line) and with the C shell only included (dashed line)...

Figure 6.29 Upper frame experimental (circles) and best-fit calculation (solid line) of the Ni K-edge XANES spectrum of the aqua ion. Lower frame experimental (circles) and best-fit calculation (solid line) of the Fe K-edge XANES spectrum of the Fe aqua ion. 2003 International Union of Crystallography.

Figure 8.7 Fe K-edge XANES spectra of sample and standard powders. CT-OB = Olfactory bulb of control group CT-BS = brain stem of control group EP-OB = olfactory bulb of exposed group EP-BS = brain stem of exposed group. FeO = FeO powder Fe203 = Fe203 powder. (Reprinted from Wang et alP 2007 Humana Press Inc.)...

Figure 41. Fe-K edge XANES spectra (a) and RDF curves describing Fe local arrangement (b) for LaFeOs (1), LaioSi4Fe2026 (2), La9.83Si4.5Fe1.5O26 (3), LaioSi5Fe026.5 (4), Fe-ZSM-5 zeolite (5).

Figure 5 Comparison of the Fe K-edge (a) and the Co K-edge (b) XANES spectra of the nanostructured host/guest compounds A and B and reference materials.

Figure 6.18 illustrates the technique with a study on a proprietary cobalt on alumina Tropsch catalyst for Fischer-Tropsch synthesis (the reaction of synthesis gas, CO + Fl2, to hydrocarbon fuels) [55]. Trace amounts of platinum help to obtain an appreciable degree of reduction for the cobalt (similarly as in the temperature-programmed reduction of bimetallic Fe-Rh catalysts in Fig. 2.4). The left part of Figure 6.18 shows Co K-edge XANES of metal and oxide reference compounds, and illustrates the strong intensity of the white line region for ionic cobalt compounds. The XANES spectrum of the calcined CoPt/A Ch catalyst re-...

The promoted WZ catalysts containing lwt% Pt and/or lwt% Fe203 were characterized by CO chemisorption and by transmission electron microscopy (TEM) in combination with EDX.33 The state of iron and its redox behavior was also analyzed by x-ray absorption spectroscopy (XANES and EXAFS at the Fe K-edge), by in situ EPR spectroscopy and by Mossbauer spectroscopy. 

Figure 4. (a). Raw XAS data for the Fe k-edge (7112 eV) of an Fe foil incorperating the XANES and EXAFS regions with the cubic spline funtion (dotted line) representing the background to be subtracted, (b). Normalized EXAFS data that has been transformed to k-space using Eq. 9. And (c). Fourier Transformed EXAFS spectrum in distance space. 

Figure 1 (a) Normalized XANES and (b) pre-edge peaks of Fe K-edge in Fe/en-MCM-41 before and after adsorption of oxyanions. 

Figure 14. Normalized, As-K edge XANES spectra of (A) As(III) and (B) As(V) in coordination environments that appear similar by XANES spectroscopy (a) in aqueous solution, (b) sorbed to smectite clay, (c) sorbed to kaolinite clay, (d) sorbed to gibbsite, and (e) coprecipitated with amorphous HAO. Panel (Q shows that similar ambiguity exists among the XANES spectra of As(V) in coordination environments containing Fe(IlI), such as precipitated in an amorphous ferric arsemite, precipitated in scorodite, and sorbed to amorphous HFO. In contrast to these XANES results, the coordination environments As(VJ species shown in panel (c) can be easily discriminated using EXAFS spectroscopy (see Fig.

Figure 3.30 Normalized Fe K-edge fluorescence XANES of (a) microcrystalline (FeTMPPbO, (b) and (c) 40% w/w (FeTMPPbO on Black Pearls (BP) high-area carbon in 0.1 M NaOH in the original oxidized state, 0.43V and in the reduced state, —0.90V versus SCE, respectively, recorded in situ (d) microcrystalline FePc. Insert cyclic voltammetry (5 mVs n) of 40% (FeTMPP)20 BP in the same solution.

Additional insight into the nature of the catalytic site was provided by the results of Fe K-edge X-ray absorption near edge structure (XANES) measurements of FeTMPPCl BP [134]. As shown in Figure 3.79, the material pyrolyzed at 800°C, as a dry powder, displays a very pronounced shoulder at energies very similar to those found for metallic Fe, which suggest that the heat treatment leads at least partially to... 

Far] Farrell, S.P, Fleet, M.E., Sulfur K-Edge XANES Study of Lokal Electronic Structure in Themary Monosulfide Solid Solution (Fe, Co, Ni)o.923S , Phys. Chem. Miner., 28, 17-27 (2001) (Experimental, Crys. Stracture, Electronic Structure, 56)... 

Fig. 2 a XANES and EXAFS at the Fe K-edge and b noimalized XANES spectra of the Ni K edge of LiNio.5Mni 5O4 at different SOCs and a Ni reftatince. Reprinted with permission from Menzel et al. [68]. Copyright (2012) by Elsevier... 

XANES (X-ray absorption near edge structure) region of the Fe K- and Co K-edge are compared in figure 5 a and b. 

FIGURE 66 Fe K pre-edge feature of Fe2Si04 collected by using conventional XANES (bottom) and Kp-detected XANES (top) (Heijboer et al., 2004). Reprinted with permission from (Heijboer et al., 2004). Copyright 2004 American Chemical Society. 

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