Application Of Graphene In The Anode Performance Enhancement Of The Microbial Fuel Cell

Microbial fuel cell(MFC) was capable of converting chemical energy of the pollutants into electrical energy using electro-active microorganisms as catalysts, which realized the synchronization of power generation with waste disposal in the same device. MFC exhibited obvious merits, such as gentle operation conditions, high security, high efficiency and unremittance running, because of which MFC was regarded as one of the most promising technology in the application of biosensor, bioremediation, sewage treatment, etc. However, the low output power density of the MFCs still limited their practical applications. It was undoubtedly that the structures and properties of the anodes were significant influence factors for the growing and the electrogenesis of the bacteria and finally affected the performance of the MFCs. In this thesis, simple and feasible approaches were applied to prepare the graphene modified anodes, such as porous grapheme anodes, hydrophilic and positively charged graphene anodes and graphene doped biofilm anodes. And the performance of these graphene modified anodes were test in single-chamber air-cathode MFCs. The main research content and results were as followed:(1) Porous graphene anodes(N/G 50 and N/G 100) were fabricated and their effect on the performance of the single-chamber air-cathode MFCs has been tested. Compared with the traditional graphene anode, these porous graphene anodes exhibited larger surface area which was conducive for the growing of the bacteria and the electron transfer in the anodic biofilms. These porous graphene anodes exhibited higher electrochemical activity and lower charge transfer resistance(Rct) compared with the traditional graphene anode. Among these porous graphene anodes, N/G 100 anode showed the upmost performance. The output voltage, the maximum output power density(Pmax) and the coulombic efficiency(CE) of the corresponding porous N/G 100 anode MFCs were obviously enhanced, which were ~0.60 V,1000 mW·m-2 and 49.34%, respectively. They were 1.88 times, 1.99 times and 2.36 times higher than that of the traditional graphene anode MFC.(2) Binder free graphene-cetyltrimethylammonium bromide(CTAB) anodes(G-CTAB-2.5, G-CTAB-5 and G-CTAB-10) with very low graphene loading were fabricated through a simple vacuum filtration strategy and their performance has been tested in single-chamber air-cathode MFCs. The surfaces of these G-CTAB anodes were hydrophilic and positively charged which were beneficial to the attachment and growing of the bacteria and among them the G-CTAB-5 anode showed the highest hydrophilicity and the largest Zeta potential. Moreover, these G-CTAB anodes also displayed higher electrochemical activity and lower Rct. The MFC with the G-CTAB-5 anode provided the highest output voltage, Pmax and CE, which were 0.57 V, 731.3 mW·m-2 and 45.74%.(3) Graphene hybrid biofilm anodes(G-0.75,G-1.5 and G-3) with different graphene doping amount were fabricated through a simple strategy and their influence on the performance of the MFCs has been tested. The doped graphene in the anodic biofilm dramatically elevated the conductivity of the biofilms and promoted the electron transfer process in it. Therefore, compared with the pure biofilm anode, the graphene hybrid biofilm anodes exhibited higher electrochemical activity and lower Rct compared with the pure biofilm anode. The G-3 anode showed the upmost performance among these graphene hybrid biofilm anodes. The starting times of the MFCs with graphene hybrid biofilm anodes have been obviously shortened and the G-3 anode MFC immediately generated electricity when the extra circuit was closed. The output voltage and Pmax of the G-3 anode MFC were ~0.53 V and 588 mW·m-2, which were 2.41 and 4.98 times larger than that of the pure biofilm anode MFC. Especially, the CE of the MFC with G-3 anode significantly increased to 73.97% from 50.03% of the pure biofilm anode MFC.