Nanostructured polypyrrole-coated anode for sun-powered microbial fuel cells.

Sun-powered or photosynthetic microbial fuel cells (PMFCs) offer a novel approach for producing electrical power in a CO(2)-free self-sustainable manner in the absence of organic fuel. Recent discovery that cyanobacteria display electrogenic activity under illumination emphasized the need to develop improved anode materials capable of harvesting electrons directly from photosynthetic cultures. Here, we showed that nanostructured electrically conductive polymer polypyrrole substantially improved the efficiency of electron collection from photosynthetic biofilm in PMFCs. Nanostructured fibrillar polypyrrole showed better performance than granular polypyrrole. Cyclic voltammetry and impedance spectroscopy analyses revealed that better performance of nanostructured anode materials was due to the substantial improvement in electrochemical properties including higher redox current and lower interface electron-transfer resistance. At loading density of 3mg/cm(2), coating of anode with fibrillar polypyrrole resulted in a 450% increase in the power density compared to those reported in our previous studies on PMFCs that used the same photosynthetic culture.