Application Of Graphene And Carbon Nano-materials Modified Anode In MFC

Microbial fuel cell (MFC) is a renewable energy device that converts organic andinorganic matter to electrical energy via the catalyzation of bacteria. It is clean,non-polluting, producing electricity while treating wastewater. However, the MFC’scommercial application is limited due to the low output power density. The electrontransfer rate between the current-producing microbes and the anode is an importantfactor in determining the battery performance. The nature and structure of the anodematerial is closely related on the adhesion of current-producing microbes, electrontransport, and substrate oxidation. Since graphene and carbon nanomaterials have ahigh conductivity, large specific surface area, it has a wide range of applications in therechargeable battery and electric catalysis.In this study, graphene and carbon nanospheres were prepared and characterized,then were made into modified anode of MFC. Then we investigated the feasibility ofmodified graphite materials as the anode in MFC and the effect on the performance ofMFC. Main results are as follows:Graphene was prepared using pressurized oxidation and ammonia-hydrazinemultiplex reduction method and the graphene was used to make graphene-modifiedanode. The optimum ratio of graphene with PTFE emulsion was studied, and tested theelectrochemical properties when graphene-modified anode applied in the MFC. Thegraphene was characterized by UV-visible、XRD、FTIR and SEM. Structural analysisshow that the graphene was very thin, and the surface was sheet fold structure, butthere were still some oxygen-containing groups on surface of graphene, such as C-O.Performance tests show that when the quality of volume ratio was1:20,the modifiedelectrode has maximum surface area, preferably wettability, contact angle was95°,the charge transfer resistance was52.05Ω, and more prone to oxidation-reductionreaction. This electrode was applied to the MFC, the results showed that the output power, output voltage, power density, redox ability of electrode, stability of the batteryhad increased, and the resistance was84Ω and decreased7%, the COD removal rate ofthe anolyte was81%. The maximum power density was424mW/m2, increased by8%than the unmodified electrode.We prepared carbon nanosphere using hydrothermal carbonization method andthe carbon nanosphere-modified anode was prepared and applied it into the MFC. Theeffects of initial concentration of glucose, temperature and time on the generation ofcarbon nanospheres was investigated, the results showed that: the initial concentrationof glucose was1.5mol/L, the reaction under200℃for16h obtained the best result,most of organic material transfer to the solid phase from liquid phase, CODswitching-in rate increased to90%, solids increased to about11g, carbon valueincreased to65%. The analysis about SEM and FTIR showed that the diameter ofcarbon nonspheres was100nm, where contains a large amount of oxygen containingfunctional groups on their surfaces, such as hydroxyl and carboxyl. The modifiedelectrode performance tests showed that: The hydrophily of carbon nonspheresenhanced and contact angle decreased to10°, the surface area increased, but redoxperformance degraded, the ohmic resistance increased to12.63Ω. The electricalproperties has not been improved when it was applied to the MFC, the resistance was164Ω and increased by80%, the maximum output power density was288mW/m2,reduced by26%, the effect of sewage treatment was lower than the unmodifiedelectrode MFC, probably because of the complexity of the composition on theelectrode surface, which affect the growth of microbial as well as electricalconductivity.