Electrochemical properties of oxygenated cup-stacked carbon nanofiber-modified electrodes.

Oxygenated cup-stacked carbon nanofibers (CSCNFs), the surface of which provides highly ordered graphene edges and oxygen-containing functional groups, were investigated as electrode materials by using typical redox species in electrochemistry, Fe(2+/3+), [Fe(CN)6](3-/4-), and dopamine. The electron transfer rates for these redox species at oxygenated CSCNF electrodes were higher than those at edge-oriented pyrolytic graphite and glassy carbon electrodes. In addition, the oxygen-containing functional groups also contributed to the electron transfer kinetics at the oxygenated CSCNF surface. The electron transfer rate of Fe(2+/3+) was accelerated and that of [Fe(CN)6](3-/4-) was decelerated by the oxygen-containing groups, mainly due to the electrostatic attraction and repulsion, respectively. The electrochemical reaction selectivities at the oxygenated CSCNF surface were tunable by controlling the amount of nanofibers and the oxygen/carbon atomic ratio at the nanofiber surface. Thus, the oxygenated CSCNFs would be useful electrode materials for energy-conversion, biosensing, and other electrochemical devices.