In a solar microbial fuel cell (SMFC), it is postulated that fuel and oxygen are regenerated internally from the electrode products by photosynthesis.  To enhance power output and advance fundamental understanding of SMFCs, we analyzed by cyclic voltammetry and microbial community characterization biocathodes of SMFCs derived from a salt-marsh inoculum.  These biocathodes exhibited a sigmoid-shaped catalytic current-potential dependency with a fairly positive midpoint potential of 0.200 V vs. Ag/AgCl that correlates with oxygen reduction. Voltammetry of SMFC biocathodes kept in darkness exhibit this same feature, indicating that non-photosynthetic members of the cathode community catalyze the electrode reaction.  Subsequent 3-electrode electrochemical cells in which working electrodes were maintained at 0.100 V and inoculated from a biofilm of a SMFC biocathode enriched in darkness developed the same voltammetric feature with substantially higher limiting current density. 16S rDNA libraries revealed a non-photosynthetic, iron-oxidizing marine bacteria belonging to the gamma-proteobacteria dominated these biofilms.

Electrochemical and microbial properties of the biocathode of a solar microbial fuel cell (SMFC)

241st National Meeting (2011)

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