2007 年 75 巻 1 号 p. 35-38
An electrocatalysis of the multi-walled carbon nanotubes (MWCNTs)/Nafion-modified edge-plane pyrolytic graphite (EPPG) electrode for the one-electron reduction-oxidation reaction of the O2/O2− (superoxide ion) redox couple in three 1-n-alkyl-3-methylimidazolium tetrafluoroborate room temperature ionic liquids (RTILs), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4), 1-n-propyl-3-methylimidazolium tetrafluoroborate (PMIBF4) and 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4) has been found. We have observed that in all the RTILs both the cathodic and anodic peak currents and the peak potential separations (ΔEp) between the anodic and cathodic peak potentials at the MWCNTs/Nafion-modified electrode are increased and decreased, respectively, compared with those at the bare electrode. The values of the standard rate constant (k0) were estimated from the ΔEp values, i.e., the k0 values at the MWCNTs/Nafion-modified electrode are (8.3±0.1)×10−3, (10.4±0.1)×10−3 and (4.2±0.1)×10−3 cm s−1 in EMIBF4, PMIBF4 and BMIBF4, respectively, while the corresponding values at the bare electrode are (4.3±0.1)×10−3, (2.9±0.1)×10−3 and (2.3±0.1)×10−3 cm s−1, respectively. The observed enhancement of the O2/O2− redox reaction is discussed briefly based on the catalytic effects and physicochemical properties of carbon nanotubes.