Raman spectroscopic investigations of activated carbon materials

Raman spectra of activated carbon materials have been investigated by a peak-deconvolution technique. It has been found as a result of our fitting trials that four Gaussians and a linear background are necessary and enough to reproduce the spectral data throughout our experiment, with a pair of relatively sharp peaks at about 1600 cm−1 and about 1350 cm−1, namely G1 and D1, and a pair of relatively broad peaks around 1560 cm−1 and 1340 cm−1, namely G2 and D2. From the characteristic behavior of these paired peaks, it has been concluded that the structure of activated carbon materials is schematically classified into two parts. The former part, represented by sharp G1 and G2 peaks, arises from winding short basal planes with bond angle order, while the latter, by broad G2 and D2 peaks, sp2 clusters like a-Cs with bond angle disorder. We have found the peak intensity ratio of G2 to G1, the I(G1)/I(G2) ratio, as a useful parameter expressing the relative content of the disorder part to the order part in the activated carbons, revealing the structural changes induced by anneal or activations. Since the changes of fitting parameters including the I(G2)/I(G1) ratio were completely opposite for H2O and KOH activation, it has been clarified that the part with bond angle disorder is selectively removed or become ordered by H2O activation, whereas induced by KOH activation, though both activation methods yield similar surface area.