In situ FTIR spectroscopy

In situ FTIR spectroscopy was used to study the adsorbed species generated on the catalyst surface in the presence of Hj and Oj. Before the experiment, the catalyst wafer was pretreated by O, (5.3 kPa) at 723 K for 1 h followed by evacuation at the same temperature in vacuum ca. 6x10 Pa) for 2 h. After the pretreatment, the temperature was decreased to a desired one in vacuum and IR spectrum was recorded at that temperature. The spectra of the catalyst wafer recorded at different temperatures were used as the background ones for the adsorption studies described below. 

As described above, the temperature needed for the formation of the adsorbed peroxide was ca. 573 K, which was almost the same as that for the initiation of the oxidation of CH to CHjOH in the presence of H, and 0,. This peroxide may directly be related to the selective oxidation of CH to CH OH. Therefore, the reactivity of this adsorbed peroxide with CH., was investigated by in situ FTIR spectroscopy as follows. 

Catalyst Activation Gas phase activation of supported DENs was examined using in-situ FTIR spectroscopy and FTIR spectroscopy of adsorbed CO. For in-situ dendrimer decomposition studies, the spectra were collected under a gas flow composed of 20% 02/He or 20% H2/He. The supported DEN sample was pressed into a self-supporting wafer, loaded into a controlled atmosphere IR cell, and collected as the sample background. The temperature was raised stepwise and spectra were collected at each temperature until little or no change was observed. After oxidation, the sample was reduced in 20% H2/He flow with various time/temperature combinations. The sample was then flushed with He for lhr at the reduction temperature. After cooling under He flow, a background spectrum was collected at room temperature. A 5% CO/He mixture was flowed over the sample for 15 minutes, followed by pure He. IR spectra of CO adsorbed on the catalyst surface were collected after the gas phase CO had been purged from the cell. 

Table 3.4 Features observed by Desilvestro and Pons (1989) during the reduction of C()2 at Pt in 0.1 M tetrabutylammonium tetra fluoro-borate (TBAF)/CH3CN. using in situ FTIR spectroscopy...

The interaction of adsorbed reactants (phenol and methanol adsorbed separately and coadsorbed) and possible reaction products of phenol methylation with the Cul-xCoxFe204 system has been studied at temperatures between lOOoC and 350oC and probed by in situ FTIR spectroscopy. The spectra of adsorbed methanol, phenol and methylated products on catalyst surface, at lOOoC, did not possess much changes compared to the spectra of pure components that indicated the molecular adsorption of species on catalyst surface. The remarkable changes in the spectra occur, above 100°C due to the chemisorption of substrates, were observed and correlated with the observed reaction trend. 

A detailed investigation of aniline N-methylation on Cui xZnxFc204 was carried out through in situ FTIR spectroscopy. The reactants (aniline and methanol) and possible products (NMA, DMA and o-toluidine) were adsorbed on the catalysts and analyzed [106,107]. Adsorption of methanol indicated a dissociative chemisorption as methoxy species on catalyst surface at 100°C. As the temperature increased, oxidation of methoxy species to formaldehyde to dioxymethylene to formate species was observed, and above 300°C complete oxidation takes place to CO, CO2 and H2. Indeed methanol alone on Cui xZnxFc204 and Cui.xCoxFc204 behaves in a similar way [79,107]. 

W. Chew Exploratory Chemometric Studies of Unmodified Rhodium Catalyzed Conjugate Diene Hydroformyla-tions via in situ FTIR Spectroscopy, PhD Thesis, National University of Singapore, 2003. 

Organized multilayers of ferrocene alkyl thiol have been self-assembled on Au(lll) under conditions of controlled thiol concentration. Several methods, such as CV, ellipsometry, STM, AFM, and in situ FTIR spectroscopy have been applied in these studies in order to find out the differences between mono- and multilayers of the same compound [152]. Similar compounds, namely, short-chain alkyl thiols (n = 3-10) with ferrocene terminal group were allowed to form organized monolayers at Au(lll) surfaces [153]. 

Applying in situ infrared spectroscopy and STM, Cai et al. [253] have studied adsorption of pyridine on Au(lll) electrodes from aqueous NaCl04 solutions. It has been found that pyridine molecule is flatly adsorbed on the surface at negative potentials. Its molecular plane rises up as the applied potential and surface concentration increase. Moreover, orientation of pyridine molecule changed with the applied STM potential. Ikezawa et al. [243] have used in situ FTIR spectroscopy to investigate adsorption of pyridine on Au(lll), Au(lOO),... 

Bjorgen, M., Lillerud, K. P., Olsbye, U., Bordiga, S. and Zecchina, A. 1-Butene oligomerization in Bronsted acidic zeolites mechanistic insights from low-temperature in situ FTIR spectroscopy. J. Phys. Chem. B, 2004, 108, 7862-7870. 

During the past 14 years, intensive work has been devoted to the study of surface film formation on noble metals in nonaqueous Li salt solutions using surface sensitive techniques. The major goal of this work had been to analyze the surface species formed at different potentials on nonactive electrode surfaces as a function of solution composition. The most successful tool has been ex situ and in situ FTIR spectroscopy [3,4,6,7,16,17], However, other techniques such as Raman [32,33], XPS [12], and EDAX have also been applied. These systems have also been studied in parallel by impedance spectroscopy [34] and EQCM [35], These measurements are complementary to the voltammetric studies de-... 

Vielstich et al. [112] studied the oxidation of PC by DEMS and FTIR spectroscopy, and Kanamura et al. studied its oxidation using in situ FTIR spectroscopy [108,109], We also studied the oxidation of other alkyl carbonate solutions (EC-DMC and EC-DEC mixtures) using in situ FTIR spectroscopy [114],... 

The chapters in this volume address challenging problems associated with the observation and interpretation of anodic dissolution of semiconductors, electrode reactions in nonaqueous solvents, and charge-transfer across the interface between two immiscible electrolytes. In-situ FTIR spectroscopy of surface reactions, and a review of electrochemical methods of pollution abatement complete the range of timely topics included. 

Adsorptivity of various ions to Langmuir monolayers has been known to be quite different from that in the bulk phase after extensive studies done by theoretical models and empirical techniques involving XPS, neutron scattering, FTIR, etc [3, 4]. Most of the empirical studies were done ex-situ because there exists difficulties in dealing with the monolayers at the air/water interface in-situ. Recently, much progress has been reported especially on the in-situ FTIR spectroscopy for the air/water interfaces [S, 6]. 

Fourier transform infrared (FTIR) and in-situ FTIR spectroscopy are among many modern instrumental tools of analytical chemistry well established in fuel-cell-related electrochemistry [1]. In general, FTIR spectroscopy is a valuable tool in the characterization of fuel cell technical electrodes, where the nature of surface groups can be identified, since such electrodes are rather difficult solid surfaces on which to work. FTIR is among the methods less commonly used for the characterization of dispersed catalysts and supports, but as a technique is able to give an idea about the nature of the surface groups on carbon supports and on the structure of adsorbed species on noble metal clusters. 

In-situ FTIR spectroscopy [95] over the Ru/Ti02 family of catalysts showed that an adsorbed CO species, located at 1985 (or 1990)cm exists on the surface of the unmodified and Ca -doped catalysts under reaction conditions, even at temperatures as high as 1073 K. This species, which was not observable over the W -doped catalyst, was attributed to CO species linearly bonded on reduced Ru sites [95]. It was concluded that the presence and population of this adsorbed CO species depend on the oxidation state and the electronic properties of the catalyst, which, in turn, depend on the type of the support employed to disperse the Ru... 

Ammonia adsorption on Lewis sites is stronger than that on Bronsted sites [97]. In situ infrared spectroscopy has been used to monitor surface coverages by various species under reaction conditions. Temperature programmed desorption shows that no NO decomposition occurs in the temperature range 100-600 K. By means of in situ FTIR spectroscopy it was observed that the fractional surface coverages by ammonia on the Bronsted and Lewis acid sites were 0.26 and 0.39, respectively, at 573 K. No adsorption of NO was found. Moreover, it was stated that water does not block the sites for ammonia adsorption. 

---