Comment on graphite intercalated with H2SO4

Salaneck, Brucker, Fischer, and Metrot [Phys Rev. B 24, 5037 (1981)] have stated that x-ray-photoelectron spectroscopic data indicate that the intercalant of the graphite-sulfuric acid system consists of species containing a variety of S/sub n/O/sub 4n/ 2- ions. We question the evidence for these peroxy sulfate species, since C17+ can be formed at potentials 0.23 to 0.38 V below that necessary to make S2O82-. The reaction of the chemically similar SO4F- species with graphite yields a product which does not contain SO4F-, suggesting that strong chemical oxidants will not be stable with respect to graphite