Methyl Viologen Mediated Oxygen Reduction in Ethanol Solvent: the Electrocatalytic Reactivity of the Radical Cation

Abstract

The study of Me viologen (MV2+) mediated O redn. in electrolytic EtOH media possesses potential application in the electrochem. synthesis of H2O2 mainly due to the advantages of the much increased soly. of O2 (O2) and high degree of reversibility of MV2+/.bul.+ redox couple. The diffusion coeffs. of both MV2+ and O2 were studied via electrochem. techniques. For the 1st time, MV2+ mediated O2 redn. in electrolytic EtOH soln. is feasible on both B-doped diamond and micro-C disk electrodes. The electrocatalytic response is due to the radical cation, MV.bul.+. The homogeneous electron transfer step probably is the rate detg. step with a rate const. of (1 ± 0.1) × 105 M-1s-1. With the aid of a simulation program describing the EC' mechanism, by increasing the concn. ratio of MV2+ to O2 electrochem. catalysis can be switched from a partial to a total catalysis regime. [on SciFinder(R)]