title: Understanding long-term changes in microbial fuel cell performance using electrochemical impedance spectroscopy.
abstract: Changes in the anode, cathode, and solution/membrane impedances during enrichment of an anode microbial consortium were measured using electrochemical impedance spectroscopy. The consortium was enriched in a compact, flow-through porous electrode chamber coupled to an air-cathode. The anode impedance initially decreased from 296.1 to 36.3 Omega in the first 43 days indicating exoelectrogenic biofilm formation. The external load on the MFC was decreased in a stepwise manner to allow further enrichment. MFC operation at a final load of 50 Omega decreased the anode impedance to 1.4 Omega, with a corresponding cathode and membrane/solution impedance of 12.1 and 3.0 Omega, respectively. An analysis of the capacitive element suggested that most of the three-dimensional anode surface was participating in the bioelectrochemical reaction. The power density of the air-cathode MFC stabilized after 3 months of operation and stayed at 422 +/- 42 mW/m(2) (33 W/m(3)) for the next 3 months. The normalized anode impedance for the MFC was 0.017 kOmega cm(2), a 28-fold reduction over that reported previously. This study demonstrates a unique ability of biological systems to reduce the electron transfer resistance in MFCs, and their potential for stable energy production over extended periods of time.
authors.affiliation: BioSciences Division and Nuclear Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6226, USA. borolea@ornl.gov
authors.forename: Abhijeet P
authors.initials: AP
authors.lastname: Borole
authors.forename: Doug
authors.initials: D
authors.lastname: Aaron
authors.forename: Choo Y
authors.initials: CY
authors.lastname: Hamilton
authors.forename: Costas
authors.initials: C
authors.lastname: Tsouris
mesh_terms: D001674:Bioelectric Energy Sources; D017097:Electric Impedance; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D008567:Membranes, Artificial; D008956:Models, Chemical; D012996:Solutions; D013057:Spectrum Analysis / Q000379:methods*; D013997:Time Factors
chemical_list: D008567:Membranes, Artificial; D012996:Solutions