An Internal Standard for Electron Spectroscopy for Chemical Analysis Studies of Supported Catalysts
Siegbahn, who introduced the technique of electron spectroscopy for chemical analysis (ESCA) for measuring binding energies of electrons in atoms, has summarized his work in two books.1,2 Several review articles have described the technique.3–6 Recent studies in these laboratories have been directed at the use of electron spectroscopy to investigate the structure of several supported metal oxides of interest in the field of catalysis. In the course of this work, we have encountered situations in which the most precise measurements possible are needed to be able to interpret with reasonable confidence relatively small shifts in electron energies. One of the important factors affecting precision, and the subject of this note, is the choice of the internal standard used. Siegbahn1 was the first to suggest that residual carbon, thought to arise mainly from vacuum pump oil contamination, could be used as an internal standard for binding energy measurements. This practice has been common in the field although some dissatisfaction with using carbon has developed.5 The use of carbon as an internal standard becomes complicated, of course, when the sample itself contains carbon. Our original ESCA studies on copper oxide supported on alumina8 utilized the carbon is energy for calibration. Subsequent work on supported catalysts has led to the use of alumina as a more satisfactory reference material.
KeywordsElectron Spectroscopy Zinc Oxide Residual Carbon Zinc Aluminate Support Metal Oxide
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