Calibration of the X‐Ray Photoelectron Spectroscopy Binding Energy Scale for the Characterization of Heterogeneous Catalysts: Is Everything Really under Control?

Abstract

Investigations of X-ray photoelectron spectra from solid samples need corrections for the surface charging effect. For powder samples such as heterogeneous catalysts and their supports, the C(C,H) component of the C 1s peak is often used as an internal standard for the calibration of the binding energy scale. Although this method is widely recognized as suitable for the study of heterogeneous catalysts, we show that a significant calibration bias can be encountered upon comparing samples with different bulk composition. In this paper, a series of SiO2 -Al2 O3 supports and Pd/SiO2 -Al2 O3 catalysts with various Si/Al ratios were studied. The spectra issued from these samples were processed with the classical calibration method on the basis of the carbon peak. Important discrepancies in the relative position of the photoelectron peaks were noticed. After systematically discarding instrument-related issues, a true chemical influence of the bulk matrix on the analyzed surface specie... Document type : Article de périodique (Journal article) Référence bibliographiqueJacquemin, Marc ; Genet, Michel J. ; Gaigneaux, Eric M. ; Debecker, Damien P.. Calibration of the X-ray photoelectron spectroscopy binding energy scale for the characterization of heterogeneous catalysts: is everything really under control?.

Hydrotalcites Promoted by NaAlO2 as Strongly Basic Catalysts with Record Activity in Glycerol Carbonate Synthesis

“…Under these conditions, the full width at half maximum (FWHM) of the Au 4f 7/2 peak of a clean gold standard sample was approximately 1.6 eV. A flood gun set at 8 eV and a Ni grid placed 3 mm above the sample surface were used for charge stabilization The C−(C, H) component of the C 1s peak of carbon was fixed to 284.8 eV to set the binding energy scale . Data treatment was performed with the Casa XPS program (Casa Software Ltd, UK); some spectra were decomposed with the least squares fitting routine provided by the software with a Gaussian/Lorentzian (85/15) product function and after subtraction of a nonlinear baseline.…”

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“…showed that the Au 4f signal from gold particles deliberately deposited on amorphous SiO 2 provides more reliable BE reference than C 1s . More recent examples indicate that the issue of correct referencing of XPS spectra remains unresolved, which contrasts with the fact that the method based on adventitious carbon is widely adopted.…”

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Investigation of surface interactions between volatile chromium species and ceramics

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