Characterization of surface oxygen complexes on carbon nanofibers by TPD, XPS and FT-IR

A fishbone type carbon nanofiber (CNF) is functionalized by different chemical and thermal treatments, and characterized by TPD, FT-IR and XPS. TPD is proved to be an effective technique to characterize surface oxygen complexes on carbon nanofibers, a novel type of mesoporous and highly graphitic carbon material. TPD spectra are analyzed by a modified deconvolution method with a multiple Gaussian function, allowing for more precise determination of each of the oxygen complexes on the surface than those reported in the literature. The surface properties of these modified CNFs measured by FT-IR and XPS are in good agreement with the TPD results. All the CNF surfaces possess more CO-producing oxygen complexes than CO2-producing ones. Different functionalization methods result in different types and distributions of oxygen complexes on the CNF surface. The gas phase oxidation of the CNF mainly increases the number and concentration of carbonyl groups, while the oxidation in the liquid phase increases those of both carboxyl and anhydride groups. Moreover, thermal annealing of CNF in an inert gas at 1700 °C strongly decreases the amount of surface oxygen complexes though CNF subsequently undergoes gas oxidation.