Influence Of The Metabolites Of Sulfate-Reducing Bacteria On Electrochemical Reduction Of Oxygen In Seawater

Sulfate-reducing bacteria (SRB) are one of the most important corrosion-inducing bacteria, whose metabolites can accelerate the corrosion process of metallic material in marine enviroment. SRB have long been considered as strictly anaerobic bacteria and most of the researches on its corrosion mechanism are focused on anaerobic conditions. Recently SRB are found to be able to survive in aerobic conditions. But there is no research on its influence of on oxygen reduction reaction. In this study, the metabolites of SRB were extracted or dissolved in 3.5% NaCl solution, whose influence on oxygen reduction reaction were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and rotating ring/disk electrode electrochemical methods.The results showed that the culture solution of SRB influenced oxygen reduction reaction. The cathodic reduction current of oxygen into superoxide and H2O2 into H2O decreased or disappeared, corresponding to the suppression of first and third step of oxygen reduction reaction. Sulfide is the main inorganic product of SRB and could react with H2O2, which is intermediate product of oxygen reduction. The addition of sulfide result in the disappearance of cathodic current for third step of oxygen reduction in CV and transmissive finite diffusion characteristics in EIS. Sulfide didn't have significant influence on first and second step of oxygen reduction reaction. Polysaccharide, uronic acid, mannose and glucose are the main organic metabolites of SRB and could suppress the first step of oxygen reduction reaction. Polysaccharide and D-glucuronic acid showed significant suppress effect on oxygen reduction reaction, which might because their adsorption on electrode decreased the ability electrode to catalyze the first step of oxygen reduction reaction.