Application Of Carbon Nanotubes And Ordered Mesoporous Carbon In Electrode Materials Of Microbial Fuel Cell

In this new century, great attentions have been focused on the new technology of energyexploration and utilization due to the increasingly serious international energy crisis andenvironmental problem. Microbial fuel cells (MFCs), as a novel, efficient bioenergyutilization technology, have attracted plentiful focus. MFCs can convert chemical energycontained in organic matter, such as organic wastewater, into electricity directly, and the finalproduct is only clean water. MFCs have a lot of advantages, such as mild reaction conditions,high energy conversion efficiency and wastewater synchronous treatment. But MFCstechnology is still in its infant currently and its future is filled with many challenges. One ofthe most serious problems limiting the engineering applications of MFCs technology is thepoor performance of its power production.The character and structure of the electrode material are closely related to the powerproduction performance of MFCs. In recent years, the carbon nano-materials have attractedmore and more attentions due to its unique molecular structure and excellent mechanical,electrical and chemical properties. A typical dual-chamber-type E. coli-MFCs wassuccessfully established, and the electrodes modified with carbon nanotubes (CNTs), orderdmesoporous carbon (OMC) and their composite were prepared. These modified electrodeswere applied to the MFCs anode or cathode, and the experiment result indicated that theapplication of these modified electrodes was beneficial to improve power productionperformance of MFCs. The research achievements have been concluded as follows:(1) As known in the preivous literature, the differences of electrode material, protonexchange membrane, inoculum bacterium, ionic strength will make the operating conditionsvary, even if the same type of MFCs, thereby the experiment resulsts in preivous literaturewere not quite valuable for reference. A typical dual-chamber MFC was established with E.coli as anode biocatalyst, glucose and yeast extract as a substrate and phosphate buffersolution (PBS) as a solution.(a) Examine the performance of the biocatalytic system of E.coli,2-Hydroxy-1,4-naphthoquinone (HNQ) and glucose, and establish the E.coli-HNQ-MFCs with carbon paper as anode and K3[Fe(CN)6] as catholyte. The open circuitpotential, internal resistance, maximum power density and the corresponding current density of MFCs power production were0.699V,300Ω,601mW/m₂and1493mA/m₂respectively.The results prove that the electron delivery efficiency of the biocatalytic system of E. coli,HNQ and glucose is high;(b) Examine the impact of different culture time of E. coli on theMFCs start-up time and output current, and the results show that24hours is the appropriatetime;(c) Examine the impact of different positive poised voltage on the MFCs start-up timeand output current, and the results show that the the greater positive poised voltage, theshorter MFCs start-up time and the greater the output current;(d) Examine the impact of theelectrode with different area on the output current density, and the results show that thecurrent densities of the electrode with different area almost the same;(e) Examine theperformance of different artificial electron mediator on electron transfer efficiency and outputcurrent of MFCs, and the results show that HNQ has higher electron transfer efficiency thanthe other familiar artificial electron mediators;(f) Examine the impact of buffer ability ofsolutions on the output current of MFCs, the results show that the use of PBS cansignificantly improve the output current and stability of MFC.(2) OMC has a BET surface area of1121m₂/g, a total pore volume of1.21cm3/g and aBJH pore size in the range of3.4-6.9nm, thereby OMC has many advantages, such as highspecific surface area, uniform nanopore distribution, high pore volume, good electricalconductivity, even high biocompatibility. The OMC modified stainless steel mesh (SSM) wasused as an anode of E. coli-MFCs, and the results indicate that (a) The use of OMC modifiedSSM (OMC-SSM) as anode of E. coli-MFCs could decrease the anode polarization obviously;(b) The open circuit potential, internal resistance, maximum power density and thecorresponding current density of MFCs power production were0.613V,350Ω,3248mW/m₂and9022mA/m₂respectively. The results show that the performance of MFCs powerproduction was improved obviously with the use of OMC-SSM anode.(3) Iron tetrasulfophthalocyanine (FeTSPc) is modified onto multi-walled CNTs(MWCNTs) through π-π stacking to synthesize FeTSPc/MWCNTs nanocomposite. Theoxygen reduction reaction (ORR) catalysis performance of FeTSPc/MWCNTs composite wasinvestigated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) andFeTSPc/MWCNTs was used as a ORR catalyst on the cathode of E. coli-MFCs. The resultsindicate that (a) In the neutral solution, the peak potential of the ORR of FeTSPc/MWCNTs positively shifted about44mV in comparison with that of commercial Pt/C catalyst (Pt/C).(b)The open circuit potential, internal resistance, maximum power density and the correspondingcurrent density of of MFCs power production were0.510V,300Ω,932mW/m₂and2792mA/m₂respectively, which were higher than those of Pt/C-MFCs.