Application Of Functionalized Carbon Nanotube Materials In Microbial Fuel Cell

In this new century, great attentions have been focused on the novel technology of energy exploration and utilization because of the international tension of energy crisis and environmental contamination. Microbial fuel cells (MFCs) are devices that use microorganism as the catalysts to oxidize organic and generate current. The unique way for power generation from MFCs provides a creative method which can be used to resolve the energy crisis and environmental contamination simultaneously. Currently, MFCs technology is still in its infant and its future is filled with many challenges. One of the most serious problems limiting the commercial and practical application of MFCs technology is the poor performance of power generation in MFCs.In this study, typical Escherichia coli (E. coli) based MFCs were selected as model system to further understand the main limiting factors in anodic process. In order to improve the performance of E. coli based MFCs, great efforts have been paid to prepare and obtain the high-performance electrode materials and cathodic oxygen reduction reaction (ORR) catalysts. Some innovative findings have been concluded as follows:(1) The conductivity of bilayer lipid membranes can greatly affect the efficiency of the electron transfer process across the cell membrane. An increasing in the conductivity of bilayer lipid membranes will promote the electron transfer across the cell membrane, which can improve the current generation in the anodic process.(2) A high anodic applying potential of 0.5 V was found to greatly promote the starting and magnitude of anodic current generated by the direct biocatalysis E. coli. This technique could be used to electroactivate and arouse the direct biocatalysis of E. coli in mediatorless MFCs.(3) Periodical discharge process can improve the performance of E. coli based MFCs. After 21 times periodical discharge, the internal resistance of E. coli based MFCs decreased from 6200 to 300Ω. And the maximum power density gradually increased from 7.16 mW m- 2 to 726.85 mW m- 2 . Comparing with the internal resistance of the cell which did not undergo a periodical discharge process, the internal resistance of the cell with a periodical discharge process decreased about 300Ω, and the maximum power density increased by 50 %.(4) Using Pt modified multi-walled carbon nanotubes (MWCNTs) composite (Pt/MWCNTs) as anodic materials can greatly improve the performance of E. coli based MFCs. The open circuit potential (OCP), internal resistance and maximum power density of the cell using Pt/MWCNTs as anodic materials are 0.90 V, 200Ωand 4302.22 mW m- 2 respectively. When four these cells are in serial, the resulting group can lighten a small light-emitting diode (LED). Besides, the cell using Pt/MWCNTs as anodic materials shows an excellent discharging behavior. There is no degradation in power output during 3 hours discharging operation (constant load of 500Ω).(5) The MnO2 modified MWCNTs composite (MnO2/MWCNTs) shows a good catalytic activity towards the ORR in neutral buffer solution, which can be used as an efficient ORR catalyst in the cathode of E. coli based MFCs. The onset potential and peak potential of ORR at MnO2/MWCNTs are 0.1 V and -0.2 V respectively. The OCP, internal resistance, and maximum power density of cell using MnO2/MWCNTs as cathodic ORR catalyst are 0.76 V, 700Ωand 1805.52 mW m- 2 respectively. The performance of this cell is higher than that of the cell using commercial Pt/C as cathodic ORR catalyst. MnO2/MWCNTs composite is a promising alternative for the expensive commercial Pt/C catalyst. However, more work is still required to improve the conductivity and stability of the MnO2/MWCNTs composite.(6) Iron phthalocyanine derivate, iron(III)tetrasulfophthalocyanine (FeTSPc), can be modified onto single-walled carbon nanotubes (SWCNTs) throughπ-πstacking. The resulting FeTSPc/SWCNTs composite shows a high catalytic activity towards the ORR in neutral buffer solution, which also can be used as an efficient ORR catalyst in the cathode of E. coli based MFCs. The onset potential and peak potential of ORR at MnO2/MWCNTs are 0.2 V and -0.02 V respectively. The OCP, internal resistance, and maximum power density of cell using FeTSPc/SWCNTs composite as cathodic ORR catalyst are 0.77 V, 400Ωand 1898.90 mW m- 2 respectively. The performance of this cell is higher than that of the cell using commercial Pt/C as cathodic ORR catalyst. FeTSPc/SWCNTs composite is a promising alternative for the expensive commercial Pt/C catalyst.