The Application Of Graphene-based Composites For Microbial Fuel Cells Anodes

Microbial fuel cells(MFCs)are novel bioelectrochemical devices,in which bacteria are used as catalysts to convert chemical energy of oxidize organic matters into electrical energy.As a sustainable and green power source,MFCs have attracted considerable attention due to their great potential in electricity generation and simultaneous wastewater treatment.However,in the case of MFCs,the low power and current densities from the low extracellular electron transfer(EET)efficiency between bacteria and electrode are still main bottlenecks for their practical applications.The anode material serveing as an area for bacterial attachment and the formation of biofilm,and also as a solid extracellular electron acceptor,weighs heavily on the power density output.Thus,it is imperative to develop novel anodic materials with specific properties that will improve the bacteria-electrode interactions but at a low cost to further improve the performance of MFCs.In this thesis,we are to explore graphene-based materials for application in MFCs anode,by combining nanomaterial with electrochemistry and biotechnology to further improve the performance of MFCs,the main works are as follows:1.Graphene/Au composites for improved electricity generation in microbial fuel cellsWe reported the use of graphene/Au(G/Au)nano-composites as a novel anode material in MFC.The current generation and power density of the MFC with the G/Au modified carbon paper(CP/G/Au)anode were significantly improved compared with conventional carbon paper(CP)and graphene modified carbon paper(CP/G),which could be attributed to the large surface area,good biocompatibility,and excellent conductivity for enhanced bacterial cells adhered to anode surface and extracellular electron transfer(ETT)efficiency.2.High biocurrent generation in microbial fuel cells using ionic liquid functiona-lized graphene nanosheets as an anodeThe positively-charged ionic liquid functionalized graphene nanosheets(IL-GNS)were prepared via a facile microwave-assisted solvothermal(MW-ST)method and used as a bioanode modifier to improve the interactions between bacterial cells and anode surface.Shewanella oneidensis MR-1 is used as a model microbe in this study,the considerable increase in electricity generation and power output was observed.The positively-charged IL-GNS can not only increase the number of negatively-charged bacterial cells adhered to the anode surface but also accelerate the inoculation of negatively-charged bacterial cells on the anode due to the electrostatic interactions.Meanwhile,the IL-GNS offer the advantages of large surface area for bacterial attachment and high conductivity to facilitate the electron transfer.Consequently,the positively-charged IL-GNS are proved to be an effective anode material to improve the performance of MFC.This novel strategy represents a promising future to use functionalized graphene for MFCs.3.Polyaniline networks grown on graphene nanoribbons-coated carbon paper with a synergistic effect for high-performance microbial fuel cellsThe graphene nanoribbons(GNRs)were prepared by longitudinal unzipping of MWCNTs and used as anode modifer to fabricate the GNRs-coated carbon paper anode(CP/GNRs).After that,PANI networks grown onto the CP/GNRs electrode were obtained by electro-deposition method and used as an anode material for MFCs.The results confirmed that the anodic current density and power density were greatly improved,indicating a synergistic effect of PANI and GNRs.On one hand,the highly conductive GNRs greatly improved the conductivity of the CP/GNRs/PANI electrode in neutral medium and incresed the large specific area and active sites for nucleation of monomers.On the other hand,PANI networks were fabricated onto the GNRs-coated carbon paper,which significantly increased the active surface area for the attachment of bacterial cells and electron transfer from mediators.In additional,the positively-charged PANI backbone improved affinitive interaction with negatively-charged bacterial cells,which enhanced the direct electron transfer via outer membrane cytochromes.Therefore,CP/GNRs/PANI electrode shows promising applications in MFCs.4.Nanostructured Graphene/TiO2 Hybrids as High-Performance Anode for Microbial Fuel CellsA novel nanostructured graphene/TiO2(G/TiO2)hybrid was synthesized via a facile microwave-assisted solvothermal(MW-ST)process,in which the amorphous TiO2 was in situ assembled on the graphene.The electrochemical properties of the hybrids as anode materials for microbial fuel cells(MFCs)were studied for the first time,and proved effective for improving MFC performance.The significant improvement for bacterial attachment and extracellular electron transfer(EET)efficiency could be attributed to the high specific surface area,active groups,large pore volume and excellent conductivity of the nanostructured G/TiO2 hybrid,suggesting that it could be a promising candidate for high-performance MFCs.