Abstract

Diffuse reflectance spectroscopy (DRIFTS) was used to monitor the in situ oxidation of carbons after a heat treatment at 1230K under flowing Ar or H ₂ to remove sulfur impurities and provide oxygen-free carbon surfaces. After heating in Ar, a carbon black progressively oxidized at 623K using an O ₂ /Ar mixture yielded spectra very similar to that obtained from a carbon black oxidized in boiling HNO ₃. Oxidation by O ₂ gave evidence for initial formation of cyclic ethers which, upon further oxidation, underwent rearrangement to form ether-like structures cross-linking polyaromatic domains. More complete oxidation by either O ₂ or HNO ₃ produced bands assigned to cyclic anhydrides, lactones, ethers, and phenols; but no bands for carboxylic acids were observed, presumably because of the absence of water vapor under our conditions. Gasification by O ₂ of the HNO ₃-treated carbon enhanced the initial bands, and also produced quinone-like structures. Surprisingly, after a heat treatment at 1230K in H ₂, this carbon black provided no discernible spectroscopic features after oxidation by O ₂, even though it was gasified. Oxidation by O ₂ of an activated Saran carbon gave results similar to those for the Ar-treated carbon black, except that essentially no absorbance was observed in the carbonyl region.