Silver nanoparticles boost performance of microbial fuel cells

Coating Shewanella bacteria with silver nanoparticles greatly boosts the performance of biofilm-based microbial fuel cells, researchers report. It achieves this effect by improving the transfer of electrons from the microbe to graphene electrodes in the fuel cells. Microbial fuel cells (MFCs) use bacteria to directly convert the chemical energy stored in organic matter to electricity by harvesting the energy generated through metabolism with electrodes. Since MFCs can use a wide range of organic fuels to create electricity, the technology is attractive for renewable power generation from biomass and wastewater treatment. Among the bacteria used to power these systems, Shewanella species are particularly well-suited for the role and have been extensively studied. However, despite considerable efforts to improve these systems, current Shewanella MFCs often suffer from low current and power densities largely limited by the inefficient transfer of electrons between the microbe and the anode. Here, Bocheng Cao and colleagues report a novel strategy for boosting the performance of Shewanella MFCs. Cao et al. found that when the bacteria are placed on a reduced graphene oxide/silver nanoparticle (rGO/Ag) anode, silver nanoparticles become associated with their cellular membranes, greatly enhancing their electron-transfer efficiency.  According to the authors, the resulting MFCs have a maximum current density of 3.85 milliamperes per square centimeter, a power density of 6.6 watts per meter squared, and a coulombic efficiency of 81%, all of which are considerably higher than other MFCs reported to date. “The optimized electron extraction and high CE reported by Cao et al. showcases that knowledge of molecular mechanisms of bacterial electron transfer can aid in designing microbial electrochemical technologies,” write Erin Gaffney and Shelley Minteer in a related Perspective.