Applicability of graphite reinforcement carbon used as the lead of a mechanical pencil to voltammetric electrodes

Abstract

Graphite reinforcement carbon (GRC), which is available as the lead of a mechanical pencil, was applied to voltammetric electrodes. This challenge was promoted by the fact that the GRC was made of highly purified carbon, that the quality was uniform, and that it promised to be usable as a disposable electrode. The polarized domains were found to be −0.8 to 0.8, −1.0 to 0.8 and −0.8 to 0.6 V (vs. SCE) in H 2SO 4, KCl and NaOH solutions, respectively. There was no wave due to adsorption or dissolution of the GRC electrode in these supporting electrolytes. The differential capacity was 25–30 μF/cm 2 for the H 2SO 4 and KC1 solutions and 40–55 μF/cm 2 for the NaOH solution at 0.0 V (vs. SCE). The peak separations for [Ru(NH 3) 6] 2+/3+ were 60 mV irrespective of the potential sweep rate v (0.005 ⩽ v/V s −1 ⩽ 0.5) in 0.4 mol/dm 3 Na 2SO 4, whereas those for [Fe(CN) 6] 4−/3− varied from 70 to 110 mV with an increase in v. The slopes of the plot of the peak current against v 1 2 were 15–20% smaller than the theoretical ones, probably because of the limitation of the effective active area in comparison with the geometrical one. The GRC exhibited specific activity to [Ru(NH 3) 6] 2+ immediately after polishing the surface. Linearity of the peak current to concentrations and v 1 2 was also retained at GRC cylindrical electrodes. The GRC electrode was applied to monitoring the system of Fe 2+/Fe 3+ in HCl solutions, which has been used for energy storage in a redox flow cell at carbon fiber cloth electrodes.