Electrochemical behavior of stainless steel anodes in membraneless microbial fuel cells

AISI 304 stainless steel was studied as cost-effective tough anodes in membraneless single chamber microbial fuel cells (SCMFCs) fed with wastewater and sodium acetate, and compared with traditional carbon cloth (CC) anodes in terms of power generation, electrochemical properties and corrosion behavior. The performances of anodic materials were evaluated using single electrode potentiodynamic polarization curves and SEM observations. The AISI 304 SS anode showed a more complex interaction between substrate and bacteria than CC anodes under the microaerophilic or anaerobic operative conditions. A strong correlation between anode and cathode productivities was demonstrated, and significantly influenced the power generation of SCMFCs. The central role of bacteria in the processes of oxygen depletion, power generation, and stainless steel corrosion was determined, and a possible rate-determining step was proposed in agreement with recent literature. AISI 304 SS localized corrosion was found only on a part of the anode where oxygen was still present (redox potential (ORP) higher than −300 mV vs. SCE). A completely anaerobic environment prevented stainless steel corrosion, without the pit formation throughout the whole experiments (2 months). These results revealed a potential use of AISI 304 SS as a cost-effective anodic material.