FTIR reflection adsorption spectra

According to experimental data,208,209 the SNIFTIR technique can be used to probe the electrical properties of the electrical double layer even in more concentrated solutions where cyclic voltammetry (cv), impedance, chronocoulometry, and other techniques are not applicable. Iwasita and Xia210 have used FTIR reflection-adsorption spectra to identify the potential at which the orientation of water molecules changes from hydrogen down to oxygen down. 

Fig. 17. FTIR reflection adsorption spectra of the novel lubricant films prepared by (a) spontaneous adsorption method and (b) LB method on the surface of the magnetic layer.

Figure 15. FTIR reflection-absorption spectra of ethyl xanthate adsorbed on gold. The concentrations and adsorption times are 10 mol dm and 10 min (a), 10" mol dm and 10 min (b), and 10 mol dm and 1 min (c). The simulated spectrum for ethyl xanthate is shown in (d). (From Ihs et al. )...

The further oxidation of this annealed [Ni0(100)+c(2x2)-0] layer is also reflected in the FTIR spectrum shown in Figure 3e. The NiO substrate in this spectrum was prepared by an additional exposure of 400 L O2 at 300 K to the annealed surface prior to the adsorption of CO. By comparing Figure 3d and Figure 3e, one can obtain important information concerning the further oxidation of the annealed NiO/Ni(100) surface. In agreement with our XPS data, the further oxidation occurs only on the c(2x2)-0 region, as indicated by the disappearance of the c(2x2)-0... 

Characterization of catalysts The zeolite structure was checked by X-ray diffraction patterns recorded on a CGR Theta 60 instrument using Cu Ka, filtered radiation. The chemical composition of the catalysts was determined by atomic absorption analysis after dissolution of the sample (SCA-CNRS, Solaize, France). Micropore volumes were measured by N2 adsorption at 77 K using a Micromeritics ASAP 2000 apparatus and by adsorption of cyclohexane (at P/Po=0.15) using a microbalance apparatus SET ARAM SF 85. Incorporation of tetrahedral cobalt (II) in the framework of Co-Al-BEA and Co-B-BEA was confirmed by electronic spectroscopy [18] using a Perkin Elmer Lambda 14 UV-visible diffuse reflectance spectrophotometer. Acidity measurements were performed by Fourier transform infrared spectroscopy (FT-IR, Nicolet FTIR 320) after pyridine adsorption. Self-supported wafer of pure zeolite (20 mg/cm ) was outgassed at 673 K for 6 hours at a pressure of lO Pa. After cooling at 423 K, the zeolite was saturated with pyridine vapour (30 kPa) for 5 min, evacuated at this temperature for 30 min and the IR spectrum was recorded. 

Figure 19 shows the reflectance spectra reported by Leppinen etal for the interaction of ethyl xanthate with chalcopyrite. The peaks at 1240 and 1260 cm" are characteristic of dixanthogen, and the spectra indicate that this species was the initial surface product. Copper xanthate has characteristic peaks near 1190 cm" and it can be seen from Fig. 19 that this compound is deposited additionally at the higher potentials applied. This order of product formation is as expected from studies of chalcopyrite oxidation (see Section VII. 1). Leppinen et found that the development of FTIR intensity correlated with the growth of voltammetric currents. No evidence was reported for adsorption of xanthate at lower potentials than dixanthogen deposition as would be expected from the UV-vis results of Richardson and Walker." The absence of a clearly discernible xanthate spectrum in the potential range expected for chemi-... 

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