Carbon nanofiber-polystyrene composite electrodes for electroanalytical processes

Carbon nanofibers provide an active and well-defined high surface area material for electroanalytical processes. In this study a novel procedure is suggested for compacting carbon nanofiber (CNF) materials (diameter typically 100-200 nm) with a polystyrene (PS) binder and additives into highly conducting and re-polishable CNF-PS composite electrodes. Three types of carbon nanofibers (Pyrograf III, 70-200 nm diameter) and a range of compositions are surveyed. A 33 wt% carbon nanofibers in polystyrene electrode provides optimum electrical conductivity and reactivity. The capacitive background current responses from CNF-PS electrodes are lowered (compared to those at glassy carbon) due to the reduced active surface area of the exposed carbon. However, faradaic currents for the reduction of Ru(NH₃)₆³⁺ at CNF-PS electrodes are approaching those for diffusion controlled processes. Resistivity measurements indicate a typical pellet resistance of 200-400 Ω mm ^-1 at 3 mm diameter. Anodic stripping voltammetry experiments for the Pb²⁺ system are reported and SEM images of electrodeposited Pb-metal are used to demonstrate the uniformly reactive surface of the CNF-PS electrode. Finally, the redox system 1,1′-ferrocenedicarboxylic acid is immobilized onto the carbon nanofibers and incorporated into the CNF-PS pellet electrodes. The voltammetric signal observed in aqueous media is consistent with release of the oxidized form of ferrocenedicarboxylic acid into solution.