Comparative 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 Methanol at Glassy Carbon and Multi-Walled Carbon Nanotube Paper Electrodes

Abstract

Comparative electrochemical and electron paramagnetic resonance study of the mechanism of oxidation of 2,3,5,6-tetra-Me-pyrazine-diN oxide as a mediator of electrocatalytic oxidation of methanol at glassy carbon and multi-walled carbon nanotube paper electrodes,

Electrochemical and quantum chemical studies of peculiarities of 2,5-di-Me-pyrazine-di-N-oxide oxidation in the presence of methanol at single-walled and multi-walled carbon nanotube paper electrodes

“…In previous studies, [16][17][18][19] in the presence of aromatic di-Noxide, a several-fold increase in the catalytic efficiency of oxidation of organic compounds at SWCNT or MWCNT paper electrodes in comparison with the GC electrode was found. It was noted [16][17][18][19] that in the absence of the substrate the oxidation current of phenazine-di-N-oxide, 2,3,5,6-tetra-Me-pyrazine-di-Noxide, at SWCNT or MWCNT paper electrodes is by several times higher than the oxidation current of the ferrocene (Fc) reference.…”

“…In previous studies, [16][17][18][19] in the presence of aromatic di-Noxide, a several-fold increase in the catalytic efficiency of oxidation of organic compounds at SWCNT or MWCNT paper electrodes in comparison with the GC electrode was found. It was noted [16][17][18][19] that in the absence of the substrate the oxidation current of phenazine-di-N-oxide, 2,3,5,6-tetra-Me-pyrazine-di-Noxide, at SWCNT or MWCNT paper electrodes is by several times higher than the oxidation current of the ferrocene (Fc) reference. Quantum chemical modeling of the adsorption energies of Pyr 1 , Fc and MeCN both on the CNT surface and in grooves between two CNTs using the cluster model simulating the surface of conducting and non-conducting carbon nanotubes 20 can explain this effect.…”

“…It should be noted that the data on Pyr 1 oxidation in the absence 20 and presence of MeOH (this paper) at MWCNT and SWCNT paper electrodes were obtained for the first time. Previously, 19 the oxidation of 2,3,5,6-tetra-Me-pyrazine-di-N-oxide (Pyr 2 ) in the presence of methanol at GC and MWCNT paper electrodes in 0.1 M solution of LiClO 4 in MeCN was studied. It is important that the absence of two methyl groups in the 2,5-di-Me-pyrazine-di-N-oxide (Pyr 1 ) molecule in comparison with Pyr 2 leads to an increase in its oxidation potential by E120 mV 18,19 and, consequently, to an increase in the reactivity of its radical cation.…”

“…Previously, 19 the oxidation of 2,3,5,6-tetra-Me-pyrazine-di-N-oxide (Pyr 2 ) in the presence of methanol at GC and MWCNT paper electrodes in 0.1 M solution of LiClO 4 in MeCN was studied. It is important that the absence of two methyl groups in the 2,5-di-Me-pyrazine-di-N-oxide (Pyr 1 ) molecule in comparison with Pyr 2 leads to an increase in its oxidation potential by E120 mV 18,19 and, consequently, to an increase in the reactivity of its radical cation. In this work the study was carried out, in contrast, 19 at both the MWCNT and SWCNT paper electrodes, and a solution of 0.1 M Bu 4 NClO 4 in MeCN was used as a background electrolyte.…”

“…It is important that the absence of two methyl groups in the 2,5-di-Me-pyrazine-di-N-oxide (Pyr 1 ) molecule in comparison with Pyr 2 leads to an increase in its oxidation potential by E120 mV 18,19 and, consequently, to an increase in the reactivity of its radical cation. In this work the study was carried out, in contrast, 19 at both the MWCNT and SWCNT paper electrodes, and a solution of 0.1 M Bu 4 NClO 4 in MeCN was used as a background electrolyte. LiClO 4 is hygroscopic, and forms several crystalline hydrates, the most stable of which is LiClO 4 Á3H 2 O.…”