Electrochemical Generation of Superoxide Ion at Sulfonated Polyaniline-modified Electrode in Alkaline Aqueous Solutions

Abstract

The water soluble sulfonated polyaniline, poly(2-methoxyaniline-5-sulfonic acid) (PMAS), was used as material for the modification of Au electrode surface in the electrochemical generation of superoxide ion (O₂⁻•) in alkaline aqueous solution. The electrochemical generation of O₂⁻• via one-electron reduction of O₂ on PMAS-adsorbed Au electrode was confirmed using the specific reaction between O₂⁻• and superoxide dismutase (SOD). PMAS adsorbed on Au electrode exhibited a reduction wave in the potential range of −0.4~−0.2 V (vs. Ag/AgCl (KC1 sat.)), in which the formal redox potential (E^0’ = −0.31 V) of O₂/O₂⁻• redox couple is, and the electroreduced form of PMAS was oxidized by O₂ molecule. It was concluded from these results that PMAS acts as a redox mediator for the reduction of O₂ to O₂⁻•. Moreover, based on the rotating disc experiments for O₂ reduction, PMAS-poly(L-ysine)-modified Au electrode was found to effectively electrogenerate O₂⁻• via the reduction of O₂.