纳米铁氧化物修饰MFC阳极的制备及其提升微生物产电性能的研究
发布时间：2018-08-13 19:29
【摘要】：微生物燃料电池(microbial fuel cell, MFC)是一种利用微生物作为催化剂氧化有机物或无机物产生电能的装置。与其他可再生能源技术相比,MFC技术可以从废水中回收以可生物降解有机物形式存在的能量,在产电的同时达到污水治理的功效,然而当前MFC的发展受到功率输出低、成本高的限制。阳极作为MFC必不可少的组成部分,直接影响产电菌的附着和电子的胞外传递,是限制MFC性能提升的关键因素,因此选用和开发合适的阳极材料对于改善MFC的产电性能、降低MFC的成本起着至关重要的作用。碳质材料因其具有生物相容性好、机械强度高、导电性好、价格低廉等优势,已成为目前最受欢迎的MFC阳极材料。Shewanella——兼性厌氧,一类重要的异化金属还原菌(dissimilatory metal-reducing bacteria, DMRB)——在MFC中作为模式产电菌而被频繁使用。铁氧化物作为天然电子受体能够被Shewanella外膜上的细胞色素C(c-type cytochromes, c-Cyts)识别而进行直接胞外电子传递(direct electron transfer, DET),受此启发我们利用纳米铁氧化物修饰碳纸电极(carbon paper, CP),以期提高产电菌的胞外电子传递(extracellular electron transfer, EET)速率从而改善MFC的产电性能,本文主要结果如下：(1)利用100℃6h原位水热法成功制备了一维(1D)α-FeOOH纳米线修饰的碳纸电极(NWs/CP),其中纳米线的直径在20-60nm,长度在650nm～1um。利用循环伏安法(cyclic voltammetry, CV)和电化学交流阻抗谱(electrochemical impedance spectroscopy, EIS)研究CP和NWs/CP的电化学活性。在进行42h时间-电流曲线(i-t)测试后,CP的电流密度为0.007mA/cm2,而NWs/CP的电流密度比CP提高了71%,达到了0.012mA/cm2,这是由于α-FeOOH纳米线修饰的CP比空白CP更有利于产电菌的附着,且修饰电极的电荷转移电阻减小。i-t测试结束后立即进行CV扫描,在-0.285V处,NWs/CP的还原峰值电流是CP的20多倍。以上结果表明原位水热法制备的修饰电极具有良好的生物相容性以及优异的生物电催化活性,因此可以用作MFC阳极。(2)利用260℃24h原位水热法成功制备了二维(2D)a-Fe2O3纳米片修饰的碳纸电极(NSs/CP),其中纳米片的宽度在5～11μm,厚度在450-800nm。在进行20h i-t测试后,NSs/CP的电流密度为0.0036mA/cm2,约为CP的1.9倍,这可归因于修饰电极电荷转移电阻的减小。i-t测试结束后立即进行CV扫描,NSs/CP的CV曲线出现了一对明显的氧化还原峰,计算得出中点电位为-0.233V(vs. SCE),这与文献报道的Shewanella外膜上c-Cyts OmcA的中点电位一致(-201mV vs. Ag/AgCl),以上说明CP修饰αt-Fe2O3纳米片后促进了产电菌利用c-Cyts OmcA进行DET,从而提高了传递效率。我们还通过控制加水量,制备了宽度分别在400-500nm、180-200nm和60-80nm的α-Fe2O3纳米片修饰的CP,电化学测试表明当纳米片的宽度由微米级减小到纳米级时,更有利于促进产电菌EET速率的提升。(3)利用100℃10h水热辅以通N2保护情况下500℃2h固相煅烧成功制备了三维(3D)a-Fe2O3介孔纳米柱阵列修饰的碳纸电极(NRs-A/CP),其中单个纳米柱的直径约在70-150nm,长度约在500-700nm。在进行48h i-t测试后,CP的电流密度为0.00640mA/cm2,而NRs-A/CP的电流密度比CP提高了62.5%,达到了0.0104mA/cm2,这可归因于修饰电极电荷转移电阻的减小。EIS测试结束后,用新鲜的DM更换半电池中的电解液,CV测试表明换液对NRs-A/CP和生物膜之间的电子传递影响极小,这可能是由于产电菌与NRs-A/CP的结合比空白CP更加紧密。
[Abstract]:Microbial fuel cell (MFC) is a device that uses microorganisms as catalysts to oxidize organic or inorganic substances to generate electricity. Compared with other renewable energy technologies, MFC can recover energy in the form of biodegradable organic substances from wastewater, which can produce electricity and achieve the effect of wastewater treatment. However, the development of MFC is limited by low power output and high cost. As an indispensable part of MFC, anode directly affects the attachment of bacteria and the extracellular transmission of electrons. It is the key factor to restrict the performance of MFC. Therefore, the selection and development of appropriate anode materials can improve the performance of MFC and reduce the cost of MFC. Carbonaceous materials have become the most popular anode materials for MFC because of their good biocompatibility, high mechanical strength, good electrical conductivity and low cost. Shewanella, facultative anaerobic, a kind of important dissimilatory metal-reducing bacteria (DMRB), is used as a model in MFC. Ferric oxide as a natural electron receptor can be recognized by cytochrome C (c-type cytochromes, c-Cyts) on Shewanella adventitia for direct electron transfer (DET), which inspires us to modify carbon paper electrode (CP) with nano-iron oxide. The main results are as follows: (1) One-dimensional (1D) a-FeOOH nanowires modified carbon paper electrode (NWs/CP) was successfully prepared by in situ hydrothermal method at 100 C for 6 h. The diameter of nanowires was 20-60 nm and the length was 650-1 um. The electrochemical activities of CP and NWs/CP were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). After 42 h time-current curve (i-t) test, the current density of CP was 0.007 mA/cm2, and the current density of NWs/CP was 71% higher than that of CP, reaching 0.012 mA/cm2. This is the result of the test. CV scanning was performed immediately after the I-T test, and the reduction peak current of NWs/CP at -0.285V was more than 20 times that of CP. The results showed that the modified electrode prepared by in-situ hydrothermal method had good biocompatibility. (2) Two-dimensional (2D) a-Fe2O3 nanosheet modified carbon paper electrode (NSs/CP) was successfully prepared by in-situ hydrothermal method a t 260 C for 24 h. The nanosheet was 5-11 micron in width and 450-800 nm in thickness. CV scanning immediately after the I-T test showed a pair of obvious redox peaks in the CV curve of NSs/CP. The calculated neutral potential was - 0.233 V (vs. SCE), which was consistent with the reported neutral potential of c-Cyts OmcA on Shewanella epimembrane (- 201 mV vs. Ag / AgCl). These results indicated that CP modified nanosheets of alpha t-Fe2O3 promoted the use of c-Cyts OmcA for DET and thus improved the transfer efficiency.We also prepared alpha-Fe2O3 nanosheets with widths of 400-500 nm, 180-200 nm and 60-80 nm respectively by controlling the amount of water added.Electrochemical measurements showed that when the width of nanosheets decreased from micron to nanometer (3) Carbon paper electrode (NRs-A/CP) modified by three-dimensional (3D) a-Fe2O3 mesoporous nanocolumn array was successfully prepared by solid-state calcination a t 500 2 h under 100 10 h hydrothermal condition with N2 protection. The diameter of a single nanocolumn was about 70-150 nm and the length was about 500-700 nm. The current density of CP was 0.00640mA/cm2, while that of NRs-A/CP was 62.5% higher than that of CP, which could be attributed to the decrease of charge transfer resistance of modified electrode. After EIS test, fresh DM was used to replace the electrolyte in the half cell. CV test showed that the electrolyte exchange affected the electron transfer between NRs-A/CP and biofilm. This may be due to the combination of NRs-A/CP and CP.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM911.45
[Abstract]:Microbial fuel cell (MFC) is a device that uses microorganisms as catalysts to oxidize organic or inorganic substances to generate electricity. Compared with other renewable energy technologies, MFC can recover energy in the form of biodegradable organic substances from wastewater, which can produce electricity and achieve the effect of wastewater treatment. However, the development of MFC is limited by low power output and high cost. As an indispensable part of MFC, anode directly affects the attachment of bacteria and the extracellular transmission of electrons. It is the key factor to restrict the performance of MFC. Therefore, the selection and development of appropriate anode materials can improve the performance of MFC and reduce the cost of MFC. Carbonaceous materials have become the most popular anode materials for MFC because of their good biocompatibility, high mechanical strength, good electrical conductivity and low cost. Shewanella, facultative anaerobic, a kind of important dissimilatory metal-reducing bacteria (DMRB), is used as a model in MFC. Ferric oxide as a natural electron receptor can be recognized by cytochrome C (c-type cytochromes, c-Cyts) on Shewanella adventitia for direct electron transfer (DET), which inspires us to modify carbon paper electrode (CP) with nano-iron oxide. The main results are as follows: (1) One-dimensional (1D) a-FeOOH nanowires modified carbon paper electrode (NWs/CP) was successfully prepared by in situ hydrothermal method at 100 C for 6 h. The diameter of nanowires was 20-60 nm and the length was 650-1 um. The electrochemical activities of CP and NWs/CP were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). After 42 h time-current curve (i-t) test, the current density of CP was 0.007 mA/cm2, and the current density of NWs/CP was 71% higher than that of CP, reaching 0.012 mA/cm2. This is the result of the test. CV scanning was performed immediately after the I-T test, and the reduction peak current of NWs/CP at -0.285V was more than 20 times that of CP. The results showed that the modified electrode prepared by in-situ hydrothermal method had good biocompatibility. (2) Two-dimensional (2D) a-Fe2O3 nanosheet modified carbon paper electrode (NSs/CP) was successfully prepared by in-situ hydrothermal method a t 260 C for 24 h. The nanosheet was 5-11 micron in width and 450-800 nm in thickness. CV scanning immediately after the I-T test showed a pair of obvious redox peaks in the CV curve of NSs/CP. The calculated neutral potential was - 0.233 V (vs. SCE), which was consistent with the reported neutral potential of c-Cyts OmcA on Shewanella epimembrane (- 201 mV vs. Ag / AgCl). These results indicated that CP modified nanosheets of alpha t-Fe2O3 promoted the use of c-Cyts OmcA for DET and thus improved the transfer efficiency.We also prepared alpha-Fe2O3 nanosheets with widths of 400-500 nm, 180-200 nm and 60-80 nm respectively by controlling the amount of water added.Electrochemical measurements showed that when the width of nanosheets decreased from micron to nanometer (3) Carbon paper electrode (NRs-A/CP) modified by three-dimensional (3D) a-Fe2O3 mesoporous nanocolumn array was successfully prepared by solid-state calcination a t 500 2 h under 100 10 h hydrothermal condition with N2 protection. The diameter of a single nanocolumn was about 70-150 nm and the length was about 500-700 nm. The current density of CP was 0.00640mA/cm2, while that of NRs-A/CP was 62.5% higher than that of CP, which could be attributed to the decrease of charge transfer resistance of modified electrode. After EIS test, fresh DM was used to replace the electrolyte in the half cell. CV test showed that the electrolyte exchange affected the electron transfer between NRs-A/CP and biofilm. This may be due to the combination of NRs-A/CP and CP.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM911.45
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