S156: Using electrochemistry to study microbial electron transport in electrode biofilms for optimal catalytic current

Electron transfer processes within the biofilms of bioelectrochemical systems are dynamic and dependent upon the organisms residing within the biofilm matrix. A number of electron transfer mechanisms have been identified for biofilm anodes of microbial fuel cells and range from electron shuttling using diffuse electron transfer mediators, to electron hopping between fixed redox cofactors. Classic electrochemical techniques such as cyclic voltammetry (CV) have been used extensively to investigate the catalytic features of microbial fuel cell biofilm anodes, and to a lesser extent, biofilm cathodes. Using CV, we have established a model for G. sulfurreducens wild type biofilm anodes indicating diffusive electron transfer via a hopping mechanism between fixed electron transfer mediators most likely to be c-type cytochromes. Based on the abundance of c-type cytochromes in G. sulfurreducens biofilms and conductivity measurements made with interdigitated microelectrode arrays (IDAs), we have developed a model for Geobacter long range biofilm electron transport dominated by superexchange, as occurs for redox polymers. We have extended our work in Geobacter to electrochemically interrogate an enriched microbial community of a biofilm cathode for applications in electrosynthesis and microbial fuel cell cathode catalysis. Advancements in our understanding of the fundamental process of biofilm electron transfer will lead to improvements in maximum achievable power for microbial fuel cells and advanced applications for biocathodes.