Characterization of Microbial Fuel Cells at Microbially and Electrochemically Meaningful Time scales

• Published in: Environmental science & technology 2011-03, Vol.45 (6), p.2435-2441
• Main Authors: Ren, Zhiyong, Yan, Hengjing, Wang, Wei, Mench, Matthew M, Regan, John M
• Format: Article
• Language: English
• Subjects: Applied sciences; Bacteria; Bacteria - classification; Bacteria - genetics; Bacteria - growth & development; Base Sequence; Biocatalysts; Bioelectric Energy Sources - classification; Bioelectric Energy Sources - microbiology; Bioelectric Energy Sources - statistics & numerical data; Biofilms; Biofilms - growth & development; Cells; Correlation analysis; Dielectric Spectroscopy; Direct energy conversion and energy accumulation; Drug resistance; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrocatalysis; Electrochemical conversion: primary and secondary batteries, fuel cells; Electrochemical Techniques; Electrons; Energy; Energy and the Environment; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Evolution; Exact sciences and technology; Fuel cells; Microbiology; Molecular Sequence Data; Refuse Disposal; Weights and Measures
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es103115a

The variable biocatalyst density in a microbial fuel cell (MFC) anode biofilm is a unique feature of MFCs relative to other electrochemical systems, yet performance characterizations of MFCs typically involve analyses at electrochemically relevant time scales that are insufficient to account for these variable biocatalyst effects. This study investigated the electrochemical performance and the development of anode biofilm architecture under different external loadings, with duplicate acetate-fed single-chamber MFCs stabilized at each resistance for microbially relevant time scales. Power density curves from these steady-state reactors generally showed comparable profiles despite the fact that anode biofilm architectures and communities varied considerably, showing that steady-state biofilm differences had little influence on electrochemical performance until the steady-state external loading was much larger than the reactor internal resistance. Filamentous bacteria were dominant on the anodes under high external resistances (1000 and 5000 Ω), while more diverse rod-shaped cells formed dense biofilms under lower resistances (10, 50, and 265 Ω). Anode charge transfer resistance decreased with decreasing fixed external resistances, but was consistently 2 orders of magnitude higher than the resistance at the cathode. Cell counting showed an inverse exponential correlation between cell numbers and external resistances. This direct link of MFC anode biofilm evolution with external resistance and electricity production offers several operational strategies for system optimization.