The mechanism of anodic over-oxidation of a 3000°C-annealed pyrolytic graphite electrode was studied by means of galvanostatic voltammetry, gravimetry, and X-ray diffractometry, in the electrolyte of 18 M sulfuric acid at 25°C.
In the early stage of over-oxidation, the X-ray diffraction line corresponding to (004) of the first stage of graphite bisulfate lamellar compound showed a continuous shift toward higher diffraction angle up to the position about 0.4° higher, without any decrease in the intensity. A slow rise of the potential of the graphite electrode was observed during the shift of (00
l) diffraction line, while the weight of the graphite electrode did not change. However, the X-ray diffraction patterns and the electrode potentials showed no measurable changes, during the further oxidation.
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