Air oxidation effects on microporosity, surface property, and CH4 adsorptivity of pitch-based activated carbon fibers

The changes in microporous structure and surface properties of pitch-based activated carbon fibers upon air oxidation were examined by high-resolution N2 adsorption and various physicochemical methods such as DTA, DRIFT, XPS, and chemical titration/analysis. It was found that air oxidation below 673 K slightly modifies the microporous structure together with a minor replacement of surface -C=O groups by -C-O groups. However, oxidation above 773 K gradually increases the specific surface area and the average width of micropores by producing micropores with larger widths and greatly induces the formation of surface functional groups, especially the -COOH group. A slight change in microporosities has an evident effect on CH4 storage property.