Reflection IR spectroscopy

Vigier F, Coutanceau C, Hahn F, Belgsir EM, Lamy C. 2004a. On the mechanism of ethanol electro-oxidation on Pt and PtSn catalysts Electrochemical and in situ IR reflectance spectroscopy studies. J Electroanal Chem 563 81-89. 

Downey and Dublin [4.22] used near-IR reflectance spectroscopy to identify the origin of the coffee beans, which have been used for the freeze dried extracts Pure Arabica, pure... 

Marinkovic et al. [50] have used in situ IR reflection spectroscopy to study adsorption of nitrate ions on Au(lll) electrodes. The ions were bonded to the gold surface via one of their oxygen atoms. Within the double-layer N03 formed contact ion pairs with hydronium ions. The extent of this process depended on the applied potential. 

We already know that PM-IRRAS combines Fourier transform mid-IR reflection spectroscopy with fast PM of the incident beam (ideally between p- and s-linear states) and with two-channel electronic and mathematical processing of the detected signal in order to get a differential reflectivity spectrum AR/... 

Diffuse reflectance spectroscopy is used when the sample consists of small particles that scatter the incoming beam (Fig. 11.14). Routine diffuse IR reflectance spectroscopy is becoming popular, because instead of forming pellets (0.1 mg of analyte ground together with KBr or Nujol and compressed to 10 to 100 atm), one can deposit a powder of the pure analyte on a surface and collect its diffuse reflectance spectrum. 

All these results may be smmnarized in Fig. 12, where all the adsorbed species (identified by in situ IR Reflectance Spectroscopy) and intermediate products (analyzed by HPLC)" are shown. 

Previously reported results provided evidence that the best activity of the R-Ru electrodes for the methanol oxidation is obtained with about 20% of Ru surface atoms. This can be roughly explained by the bifimctional mecharrism, taking irrto account the number of surface sites necessary to accommodate all the intermediates adsorbed, as observed by IR reflectance spectroscopy (Scheme 1). ... 

These pioneering results on smooth platinum obtained by EMIRS were confirmed by the new IR Reflectance Spectroscopy developed by Pons et al. (SNIFTIRS) and Weaver et al. (SPAIRS), able to observe intermediate species produced on carbon (e.g. Vulcan XC-72) supported Pt-based nanoparticles. 

Modification of Pt by tin greatly enhances the electrooxidation rate of ethanol " and may change the reaction mechanism, so that the adsorbed species and reaction intermediates were also investigated by IR reflectance spectroscopy. 

Taking into acconnt previous IR reflectance spectroscopy studies and the results obtained here, a general mechanism can be proposed for the electrocatalytic oxidation of ethanol at a platinum electrode (Scheme 2). 

Scheme 2. Proposed mechanism for the electrocatalytic oxidation of ethanol on smooth platinum in acidic medium during the positive potential sweep (all the species with colored filling were detected either by IR reflectance spectroscopy or by chromatographic analysis).

Some support for this arises from the observation by in situ IR reflection spectroscopy (70, 71) that chemisorbed CO is formed as a self-inhibiting species in the electrooxidation of HCOOH at, for example, Pt, where the main reaction sequence is... 

The study of the interaction mechanism of thin films of BACY prepolymer on different surface states of Si and oxidized Al employing advanced techniques such as XPS, UPS, MIES, IR reflection spectroscopy, and AFM was undertaken by Possart and Dieckhoff [364]. The trioxy triazine was the only moiety identified to have adhesive interaction with the substrate. On a Si surface, the mechanism was identified as donor-acceptor interaction where the lone pairs of electrons on N and O atoms of trioxy triazine were involved in the electron donor process for the Si cation. On aluminum oxide, the Lewis acidic OH groups act as electron acceptors, withdrawing electron density from the lone pairs of O and N of the trioxy triazine. Back donation of electron density from Al metal to the organic layer is operative beneath the oxide layer. The dicyanate monomer doesn t adhere at all and desorbs quickly out of the interphase region on the substrate. It was concluded that thermosetting reaction of the prepolymer is thus hampered and the resulting network will be less dense near the substrate than in the bulk. 

In Ch. 24 Aoki uses FT-IR reflection spectroscopy to monitor the transfer of protons and of water molecules from a layer of H2O ice to a layer of D2O ice as a function of time and external pressure. The H/D mutual diffusion coefficient measured at 400 K shows a monotonic decrease by two orders of magnitude as the pressure increases from 8 to 63 GPa. In order to separate molecular from protonic diffusion experiments were also carried out on H2 0 ice bilayer. 

In situ electro-optical reflection is a very promising means for meeting this need. There are two such methods, internal and external reflection methods the latter includes specular reflection spectroscopy, ellip-sometry, IR reflection spectroscopy, and surface enhanced Raman scattering (SERS). 

Ishida H, Ishino Y, Buijs H, Tripp C and Dignam M J 1987 Polarization-modulation FT-IR reflection spectroscopy using a polarizing Michelson interferometer App/, Spectrosc. 41 1288-94... 

The study of the electrosorption and oxidation of formaldehyde follows the patterns presented above. Thus electrochemically modulated IR reflectance spectroscopy (EMIRS) was used to identify the adsorbed species formed at different potentials in the... 

Immobilization immobilized aqueous phase in situ IR reflectance spectroscopy in situ IR transmission spectroscopy in situ NMR spectroscopy... 

The oxidation of ethanol is more difficult than that of methanol with the necessity to break the C-C bond to obtain its complete oxidation to CO2. It was observed by in situ IR reflectance spectroscopy that the dissociation of ethanol leads also to the formation of adsorbed CO [8]. This is the proof that the C-C bond can be, at least to some extent, broken at room temperature and that carbon dioxide can be obtained. However, the main oxidation products are... 

The electrocatalytic oxidation of ethanol has been investigated for many years on several platinum-based electrodes, including Pt-X alloys (with X = Ru, Sn, Mo, etc.), and dispersed nanocatalysts. Pure platinum smooth electrodes are rapidly poisoned by some strongly adsorbed intermediates, such as carbon monoxide, resulting from the dissociative chemisorption of the molecule, as shown by the first experiments in infrared reflectance spectroscopy [8]. Both kinds of adsorbed CO, either linearly-bonded or bridge-bonded to the platinum surface, are observed. Besides, other adsorbed species have been identified by IR reflectance spectroscopy, including reaction intermediates, such as acetaldehyde and acetic acid, and other by-products [9]. 

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