Methylene blue was immobilized on 304L stainless steel to investigate a potential cost-effective, durable, and high performance composite electrode for use with microbial applications, such as bio-batteries and microbial fuel cells. The composite electrodes were tested in dual-chamber bio-batteries with pure cultures of Escherichia coli K-12 or Shewanella oneidensis MR-1 and the results were compared to those obtained using bare graphite electrodes. The maximum power generated using the composite electrodes was 39.35 mW m−2 in bio-batteries using E. coli K-12, and 60.05 mW m−2 in bio-batteries using S. oneidensis MR-1. Compared to graphite electrodes, the bio-batteries using composite electrodes showed a 6- and 2.5-fold increase in the maximum power density, using pure cultures of E. coli K-12 and S. oneidensis MR-1, respectively. The composite electrodes did not inhibit bacterial growth in the bio-batteries and were shown to improve performance (both in terms of power output and current density) over conventional graphite electrodes.
