In situ laser Raman spectroscopy

With the aim to study the characteristics of VPO catalysts in the course of butane oxidation to maleic anhydride together with a simultaneous evaluation of the catalytic performance, we have used Raman spectroscopy which is a very sensitive probe for determining the presence of V0P04-like entities together with (VO)2P207. An in situ Laser Raman Spectroscopy (LRS) cell was built in our laboratory (6). In the corresponding publication (6 ), the preparation and the characterization by XRD, Ip... 

E. Payen, S. Kasztelan J. Grimblot (1988). J. Mol. Struct, 174, 71-76. In situ laser Raman spectroscopy of the sulfiding of W03(Mo03)gamma-Al203 catalysts. 

Chan, S., Wachs, L, Murrell, L., et al (1984). In Situ Laser Raman Spectroscopy of Supported Metal Oxides, J. Phys. Chem., 88, pp. 5831-5835. 

Centi, G. (1993). Vanadyl Pyrophosphate A Critical Overview, Catal. Today, 16, pp. 5-26. Ben Abdelouahah, F., Olier, R., Guilhaume, N., et al. (1992). A Study By In Situ Laser Raman Spectroscopy of VPO Catalysts for n-Butane Oxidation to Maleic Anhydride I. Preparation and Characterization of Pure Reference Phases, J. Catal., 134, pp. 151-167. 

Ben Abdelouahab F.B., Olier R., Guilhaume N., Lefebvre F. and Volta J.-C. (1992). A study by in situ laser Raman spectroscopy of VPO catalysts for n-butane oxidation to maleic anhydride. I. Preparation and characterization of pure reference phases, J. Catal, 134, 151-167 Benabde-louahab F.B., Volta J.-C. and Olier R. (1994). New Insights into VOPO4 Phases Through Then-Hydration, J. Catal, 148, pp. 334-340. 

H.-B. Zhang and G. L. Schrader, Characterization of a fused iron catalyst for Fischer-Tropsch synthesis by in situ laser Raman spectroscopy, Journal of Catalysis, vol. 95, no. 1, pp. 325-332, 1985. 

Photoeffects at copper electrodes coated with copper phenylacetylide (CuPA) films were discovered during an in-situ laser Raman investigation [35], where substantial cathodic photocurrents were observed. A subsequent detailed study by photocurrent spectroscopy showed that the photocurrent conversion efficiency was of the order of a few percent, even for thicker films which absorbed a substantial fraction of the incident light. Figure 18 contrasts the photocurrent excitation spectrum with the absorption spectrum measured on an OTE coated with the CuPA polymer. The coincidence in the vibrational structure in the two spectra is striking, suggesting that the absorption gives rise to a state with considerable molecular character. 

Figure 5 presents the experimental setup of in situ electrochemical Raman spectroscopy. The instrument for in situ Raman spectroscopic studies of electrochemical systems includes a laser as the excitation source, a Raman spectrometer, a personal computer for control of the Raman spectrometer, data acquisition and manipulation, as well as a plotter or printer for data output, a potentiostat /galvanostat and possibly a wave function generator for generation of various kinds of po-tential/current control over the electrode, and the spectroelectrochemical cell. Details of electrochemical instrumentation were given in Chapter 1.2 see this chapter for various definitions, including WE... 

These models are designed to define the complex entrance effects and convection phenomena that occur in a reactor and solve the complete equations of heat, mass balance, and momentum. They can be used to optimize the design parameters of a CVD reactor such as susceptor geometry, tilt angle, flow rates, and others. To obtain a complete and thorough analysis, these models should be complemented with experimental observations, such as the flow patterns mentioned above and in situ diagnostic, such as laser Raman spectroscopy. 

Of special Interest as O2 reduction electrocatalysts are the transition metal macrocycles In the form of layers adsorptlvely attached, chemically bonded or simply physically deposited on an electrode substrate Some of these complexes catalyze the 4-electron reduction of O2 to H2O or 0H while others catalyze principally the 2-electron reduction to the peroxide and/or the peroxide elimination reactions. Various situ spectroscopic techniques have been used to examine the state of these transition metal macrocycle layers on carbon, graphite and metal substrates under various electrochemical conditions. These techniques have Included (a) visible reflectance spectroscopy (b) laser Raman spectroscopy, utilizing surface enhanced Raman scattering and resonant Raman and (c) Mossbauer spectroscopy. This paper will focus on principally the cobalt and Iron phthalocyanlnes and porphyrins. 

The electrochemistry and cristallography of the nickel oxides have been extensively investigated in connection with the improvement of storage batteries . In-situ UV/visible reflectance spectroscopy and laser raman spectroscopy of the... 

Laser Raman spectroscopy has played a major role in the study of electrochemical systems (see Section 3.4). The technique provides molecular-specific information on the structure of the solid-solution interfaces in situ and is particularly suited for spectroelectrochemical studies of corrosion and surface film formation. Metals such as Pb, Ag, Fe, Ni, Co, Cu, Cr, Ti, Au and Sn, stainless steel and other alloys in various solutions have been studied by the technique. 

Israel, E.J., Arvidson, R.E., Wang, A., Pasteris, J.D. Jolliff, B.L. (1997) Laser Raman spectroscopy of varnished basalt and implications for in situ measurements of Martian rocks. Journal of Geophysical Research - Planets 102(El 2), 28705-28716. 

In this study, suboxides of vanadia catalysts were used in pentane, pentene, dicyclopentadiene and cyclopentane oxidation reactions. In the previous phase of the work [12,13], the role of alkali promoters on the catalyst selectivity was examined. The catalysts were reduced in situ at different temperatures and the effect of pre-reduction temperature was investigated. Controlled-atmosphere characterization of pre-reduction, post-reduction, and post-reaction catalysts were performed using X-ray diffraction. X-ray photoelectron spectroscopy, laser Raman spectroscopy and temperature-programmed desorption experiments. The objectives of this study were to determine the activity and selectivity of different suboxides of vanadia in... 

Laser Raman spectroscopy has been applied to materials characterization studies over the past several years. Annual reviews discuss advances in the field and provide references for a number of specialized areas including thin film analysis (1). The attractive features for using Raman spectroscopy to evaluate thin films include a nondestructive j n situ measurement capability plus the ability to acquire both spatially and time-resolved vibrational data from which structural information can be inferred. 

FI. Knozinger and G. Mestl, Laser Raman spectroscopy—a powerful tool for in situ studies of catalytic materials. Topics in Catalysis, vol. 8, pp. 45-55, 1999. 

Fourier Transform Infrared Spectroscopy (FTIR) and Laser Raman Spectroscopy (LRS) provide complementary views of chemical bonding in a sample by studying the vibrational energies of the bonds. Siu ace Enhanced Raman Spectroscopy (SERS) can give vibrational spectra of in situ films. A useful review of the apphcation of these vibrational spectroscopies is available [79]. 

The reaction investigation of ammonia synthesis on iron catalj ts by laser Raman and in situ FT-IR spectroscopy showed that the main chemisorbed species were molecular state N2(ad) rather than atomic one N (ad). The analysis with AES by Spencer et al. showed that N (ad) was of very high coverage on... 

The future of Raman microspectroscopy is probably imaging and optical near-field nano-Raman spectroscopy [529], cfr. Chp. 5.5.2. While conventional laser Raman spectroscopy samples 10 g (mm ), /zRS handles 10 g (nm ) and near-field Raman spectroscopy 10 g (nm ). Mobile Raman microscopy (MRM) allows in situ Raman analysis [530]. One can expect further developments in the field of NIR multichannel Raman spectroscopy with the advent of 2D array detectors offering extended response in the NIR. With these 2D sensors it wiU become possible to apply in the NIR region the powerful techniques already developed in the visible, such as confocal line imaging techniques or multisite remote analysis with optical fibres. 

Perhaps the best known and most used optical spectroscopy which relies on the use of lasers is Raman spectroscopy. Because Raman spectroscopy is based on the inelastic scattering of photons, the signals are usually weak, and are often masked by fluorescence and/or Rayleigh scattering processes. The interest in usmg Raman for the vibrational characterization of surfaces arises from the fact that the teclmique can be used in situ under non-vacuum enviromnents, and also because it follows selection rules that complement those of IR spectroscopy. 

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