Adsorption sites diffraction studies

The CG picture of the structure of the water network in VPI-5 molecular sieve as reported by the high resolution synchrotron powder diffraction study[7] is shown in Fig. 5. As mentioned earlier, quantum chemical cluster model calculations by MNDO method have also shown that the energetically favourable sites for the adsorption of water is in correspondence with the experimental reports. 

T[ie results of the present study have shown that the ammoxidation activity of the catalysts depends on the oxidation number of vanadium in the catalysts. The oxidation number of vanadium and irreversible O2 and NH3 uptakes increase in the same fashion as the ammoxidation activity of the catalyst suggesting that adsorption sites and the active sites increase with increase in V2O5 loading up to a monolayer coverage. X-ray diffraction studies have shown that anatase is the major phase in all the catalysts. Transformation of anatase to... 

Used for the study of adsorption site symmetry of molecules on single crystal surfaces such as in the production and observation of synthetic catalytic intermediate species at high coverage. There are overlaps with techniques such as LEED (low energy electron diffraction) and SEXAFS (surface X-ray absorption fine structure). 

In order to get answers to these questions, the ability to better characterize catalysts and electrocatalysts in situ under actual reactor or cell operating conditions (i.e., operando conditions) with element specificity and surface sensitivity is crucial. However, there are very few techniques that lend themselves to the rigorous requirements in electrochemical and in particular fuel cell studies (Fig. 1). With respect to structure, in-situ X-ray diffraction (XRD) could be the method of choice, but it has severe limitations for very small particles. Fourier transform infra red (FTTR), " and optical sum frequency generation (SFG) directly reveal the adsorption sites of such probe molecules as CO," but cannot provide much information on the adsorption of 0 and OH. To follow both structure and adsorbates at once (i.e., with extended X-ray absorption fine stmcture (EXAFS) and X-ray absorption near edge stmc-ture (XANES), respectively), only X-ray absorption spectroscopy (XAS) has proven to be an appropriate technique. This statement is supported by the comparatively large number of in situ XAS studies that have been published during the last decade. 16,17,18,19,20,21,22,23,24,25 highly Versatile, since in situ measme-... 

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