engleski

CATALYST COMPOSITION FROM THEORETICAL MODEL OF RAMAN SPECTRA

Raman spectroscopy is optical resonance technique sensitive to atomic bonding. As such it is often used for catalyst characterization and for the investigation of the bulk and surface chemistry during catalyst use. Method is of considerable interest in situations when catalyst is not single-phase material, but consists of a mixture of crystal phases. Ideally, in such cases, Raman spectra in comparison with theoretical model would be indispensable tool for description of physicochemical properties of these complex structures including phase contacts. Modeling the Raman spectra, however, even at the level of density-functional theory proves to be rather computationally demanding. In the attempt to elucidate catalyst composition, and complement experimental findings (XRD, XPS, Raman spectroscopy) in our research of MnMOx catalysts, we begin by modeling separate crystal phases expected to be present in the multi-phase catalyst samples [1]. To some extent, the interfacial effects are accounted for by the finite size of the theoretically studied structures representing crystallites. Based on comparison of weighted superposed theoretical spectra of several crystal phases and experimental Raman spectra of the catalyst, we comment on the possibility to use such approach for determination of multi-phase catalyst composition and investigation of its properties.

DFT, Raman spectra, multi-phase catalyst

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