Electrochemical and electron paramagnetic resonance study of the mechanism of oxidation of 2,3,5,6-tetra-Me-pyrazine-di-N-oxide as a mediator of electrocatalytic oxidation of isopropyl alcohol at glassy carbon and single-walled carbon nanotube electrodes

Abstract

The mechanism of oxidation of 2,3,5,6-tetra-Me-pyrazine-di-N-oxide (Pyr2) as a mediator of electrooxidation of isopropyl alcohol was studied by cyclic voltammetry at glassy carbon (GC) and single-walled carbon nanotubes (SWCNT) electrodes in 0.1M LiClO4 solutions in acetonitrile. The adsorption of Pyr2 at SWCNT electrode in 0.1M LiClO4 solution in acetonitrile was investigated by measurement of the dependence of the differential double layer capacitance of the electrode C on potential E. The effect of isopropyl alcohol on the shape of cyclic voltammograms (CVs) of Pyr2 and the intensity of EPR signal of its radical cation was investigated. The catalytic currents were recorded at the oxidation of Pyr2 at SWCNT and GC electrodes in the presence of isopropyl alcohol. The effect of acid and water (as a base) on the catalytic process was studied. The results were explained in terms of the E1C1E2C2 mechanism of two-stage electrode process characterized by catalytic current recorded at the second electrode stage. The overall two-electron catalytic oxidation of isopropyl alcohol in complex with the Pyr2 radical cation was assumed to occur. It was found that the use of SWCNT electrode instead of GC one increases the catalytic efficiency of i-PrOH oxidation by 17 times.