Applicability of surface spectroscopies in catalyst characterization

This section considers the applicability of the four principal surface analytical techniques that are usually applied to catalyst surface characterization. They are XPS (coexisting acronym is ESCA which also includes XAES), AES, SIMS, including its nondestructive static SIMS mode and the use of neutral atoms as primary particles in fast atom bombardment mass spectrometry (FAB-SIMS or FABMS), and last, ISS. 

XPS is the most commonly used and most useful surface analysis method in catalyst characterization. It can be used for both qualitative and quantitative analysis for almost all kinds of catalysts used in heterogeneously catalyzed reactions. XPS studies of oxide, sulfide, fluoride, halide, etc., catalysts,. supported metal catalysts, Raney or gauze metal catalysts and zeolite catalysts are all possible. The samples can be studied in any of the precursor, calcined, reduced, activated, deactivated, aged or poisoned states. Real industrial catalysts can be analyzed as well as fundamental model systems. Quantitative analysis is possible either with the help of empirical sensitivity factors or by standard-free methods. In the latter case appropriate theoretical models are u.sed with photoionization cross-section tables, inelastic mean free path (X.) data and individ- 

The analysis must be carried out under good high-vacuum conditions, at the worst, and preferably UHV, 

The analysis can suffer from line interference, which may occur easily with multicomponent cataly.st samples. 

Detection of minority constituents ( 1 at.%) can be impossible due to lack of sensitivity. 

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