Multifunctional Nanomaterials For Microbial Biofuel Cell Anodes

Microbial fuel cells?MFCs?harness the metabolic machinery of microorganisms to directly convert chemical energy into electrical energy.As an integrated technology to address energy generation and environmental bioremediation simultaneously,MFCs have drawn much attention in recent years.However,their practical application is heavily limited by their relatively low power density and short lifetime.Among numerous factors,the anode material undertakes the function of providing area for bacterial attachment and extracellular electron transfer?EET?,highly influencing the overall performance of MFCs.In this dissertation,we have explored to choose carbon-base materials,conducting polymers and metal oxides as primary material,and fabricate multifunctional nanocomposites with good biocompatibility,excellent conductivity,enhanced surface properties and optimized structures to obtain high-performance MFCs as well as advance the commercialization of MFCs.The main contents are as follows:1.G/Fe₃O₄ Nanocomposites as Efficient Anodes to Boost the Lifetime and Current Output of Microbial Fuel CellsA novel anode material,graphene/Fe₃O₄?G/Fe₃O₄?composite,has been designed for MFCs.Because the Shewanella species could bind to Fe₃O₄ with high affinity and their growth could be supported by Fe₃O₄,the bacterial cells attached quickly onto the anode surface and their long-term activity improved.As a result,MFCs with reduced stratup time and improved stability were obtained.Additionally,the introduction of graphene not only provided a large surface area for bacterial attachment,but only offered high electrical conductivity to facilitate extracellular electron transfer?EET?.The results showed that the current and power densities of a G/Fe₃O₄ anode were much higher than those of each individual component as an anode.2.Bacteria-Affinity 3D Macroporous Graphene/MWCNTs/Fe₃O₄ Foams for High-Performance Microbial Fuel CellsWe have devised a novel interconnected three-dimensional?3D?Macroporous framework of graphene sheets incorporated with Fe₃O₄ nanospheres and MWCNTs?3D G/MWCNTs/Fe₃O₄ foams?via one-pot solvothermal process and freeze-dry method.In this multi-componet architecture,3D macroporous graphene framework render the electrode inner surface accessible for bacterial colonization.In order to prevent graphene sheets from restacking and promote the conductivity of the nanocomposites,multi-walled carbon nanotubes?MWCNTs?was designed as intercalated spacer.Moreover,Fe₃O₄ nanospheres were utilized as bio-affinity anchors for improving the bacterial loading capacity of electrode and keeping the long-time activity of bacteria.In this case,the anode possessed high bacterial-hosting capability,excellent biocompatibility as well as enhanced electron-accepting ability.With these merits,the constructed MFCs possessed significantly higher power output and stronger stability than that with conventional graphite rod anode.3.Inkjet-Printed Porous Polyaniline Gel as an Efficient Anode for Microbial Fuel CellsInkjet-printed Polyaniline?PANI?gel on carbon paper was first fabricated and then successfully employed as anodes in MFCs.Thanks to the inkjet-printing technology,such anodes possessed facile fabrication process,highly scalable size and good repeatability.Moreover,these anodes possessed good conductivity and a porous structure,as well as the ability to electrostatically interact with bacterial cells,which contributed to a 6.1-fold increase in the output power over that of unmodified carbon paper.Clearly,our study not only provides a new opportunity to push the practical application of MFCs technology,but also adds a new dimension to the application of inkjet-printing technology.4.Polypyrrole encapsulated exoelectrogens for High-Performance Microbial Fuel CellsBy taking advantage of in situ polymerization,we have developed polypyrrole?PPy?coated exoelectrogens as anode for MFCs.In PPy coated exoelectrogens,the PPy offered electrical conductivity across the cell surface without affecting cell viability.As the c-type cytochromes existence on the out menbrane of Shewanella ondidensis MR-1,the coating of PPy on the surface of exoelectrogens largely enhanced direct contact-based extracellular electron transfer,thereby contributing to a significantly increase in the current of MFCs over that of natural exoelectrogens.Moreover,PPy coatings were successfully formed on three other bacteria cells without affecting viability,which highlight the potential of employing PPy as conducting coating for a variety of basic biological units.