Untangling the intricacies of redox reactions on Poly(3,4-ethylenedioxythiophene) in anoxic bacteria environment

Poly(3,4-ethylenedioxythiophene) (PEDOT) film, electrochemically polymerized on stainless steel, was subjected to testing in an anoxic environment containing sulfate-reducing bacteria (SRB). Results of the electrodes’ open circuit potentials demonstrate that the PEDOT film was seamlessly discharged by electrons given up by substrate oxidation in the bacteria culture. Subsequently, the PEDOT film was reoxidized by mediating sulfate reduction reactions (catalyzed by SRB) on the steel surface to keep the polymer film conducting, thus ensuring the reversibility of redox reactions. The polymer degradation ensued following prolonged exposure of the PEDOT film to the bacteria environment, evidenced by the formation of carbonyl groups in the polymer's backbone, depletion of elemental carbon, increased surface roughness, and a 74 % resultant decrease in electrode capacitance in 24 h of testing. Galvanic interaction between the CP and the steel substrate was crucial to maintaining the reversible redox reactions on the PEDOT film.