微生物燃料电池阴极孔隙结构和表面优化及产电性能研究

发布时间：2018-07-06 18:22

本文选题：微生物燃料电池 + 催化层孔隙率　；参考：《哈尔滨工业大学》2016年博士论文

【摘要】：微生物燃料电池(Microbial fuel cell,MFC)是利用电极微生物的催化作用将污水中有机物的化学能转变为电能的生物电化学系统。在单室空气阴极MFC中,活性炭阴极因其成本低廉,易于放大等优点得到广泛关注。然而,阴极催化性能依然较低,长期运行稳定性较差。本文针对辊压活性炭阴极进行研究,考察了催化层孔隙结构及微生物的附着对阴极活性的影响及作用机理,并通过表面优化制备了催化活性高且具有抗生物污染特性的阴极材料,考察了电极长期运行性能。通过向活性炭催化层中掺杂NH4HCO3造孔剂可有效改变催化层孔隙结构。在活性炭:造孔剂(质量比)为5:1时,催化层孔隙率及孔面积分别增加37.8%及3.3倍,小孔(0.8μm)孔隙率增加28.4倍。孔隙结构的增加不仅促进了氧气向催化位点的传质,而且拓展了阴极三相界面,阴极电化学活性明显提高。与未添加造孔剂阴极相比,通过NH4HCO3的成孔作用,MFC最大功率密度提高32.9%。该阴极具有更加稳定的运行性能,经过4个月的运行,阴极扩散内阻增加,导致MFC产电性能逐渐下降,但活性炭阴极MFC的功率密度仅下降12.7%,低于传统Pt/C阴极MFC的35.1%。经过6个月的运行,活性炭阴极表面被生物膜完全覆盖,而催化层内部的部分孔隙也被生物膜堵塞,致使阴极三相反应界面及电极氧传质能力降低,从而抑制了阴极的催化活性。经过清除表面生物膜及进一步去除孔隙内部生物膜,电极氧传质能力得以增加,交换电流密度分别极高8.6%及34.5%,电荷传递内阻分别降低23.1%及44.0%,MFC最大功率密度逐步恢复;当阴极去除活性炭催化层时,生物膜的生长导致电极电流输出降低及过电位增加,阴极的生物膜没有氧还原催化作用。合成了活性炭负载纳米银催化剂及制备了LA132粘结剂修饰的亲水性催化层,获得了催化活性高、抗生物污染效果好的空气阴极。活性炭负载纳米银后,MFC最大功率密度提高了14.6%。经过150天的运行,阴极表面生物膜中蛋白含量仅为活性炭空气阴极的38.3%。电极表面少量的生物膜不仅利于阴极界面氧气的传输,也缓解了OH-由催化层向主体电解质的传质阻力,阴极过电位得以降低;通过在PTFE粘结剂中加入LA132粘结剂,活性炭催化层的亲水性逐渐提高,增加了三相界面的可润湿性,促进了质子向反应位点的传质。当复合粘结剂中LA132的比例为67%时,MFC最大功率密度提高了13.9%。在提高亲水性的同时,LA132粘结剂的修饰也增加了催化层表面电负性,因此有效抑制了微生物的附着及生物膜的生长。经过150天的运行,该阴极生物膜中的蛋白含量仅为PTFE阴极的52.5%。利用上述制备的阴极考察其在单室MFC中以生活污水为底物的产电能力。与PTFE阴极电压(323±44 mV)及功率密度(411±5 mW/m2)相比,复合粘结剂阴极获得更高的输出电压398±15 mV及功率密度454±24 mW/m2。同时,MFC反应器出水中的COD及TN去除率分别达到90.2±3.6%及80.3±8.3%。通过降低外电阻可提高MFC的电流密度,同时增加COD及TN的去除速率。
[Abstract]:Microbial fuel cell (MFC) is a bioelectrochemical system that uses the catalysis of electrode microbes to transform the chemical energy of organic compounds in sewage into electric energy. In the single chamber air cathode MFC, the active carbon cathode is widely concerned because of its low cost and easy amplification. However, the catalytic performance of the cathode is still low. The long-term operation stability is poor. In this paper, the roll pressed activated carbon cathode was studied. The influence and mechanism of the pore structure of the catalytic layer and the attachment of microorganism on the cathodic activity were investigated. The cathode materials with high catalytic activity and biological pollution resistance were prepared by surface optimization, and the long-term performance of the electrode was investigated. The pore structure of the catalytic layer can be effectively changed by doping NH4HCO3 pore forming agent in the activated carbon catalytic layer. In the activated carbon, the porosity and pore area of the catalytic layer are increased by 37.8% and 3.3 times respectively, and the porosity of the pore (0.8 mu m) increases by 28.4 times. The increase of pore structure does not only promote the mass transfer of oxygen to the catalytic site, but also expands. The cathodic electrochemistry activity of the cathode is obviously improved. Compared with the cathode of no pore forming agent, the maximum power density of MFC is enhanced by the pore forming effect of NH4HCO3. The cathode has a more stable operating performance. After 4 months' operation, the internal resistance of the cathodic diffusion is increased and the conductivity of the MFC is gradually reduced, but the active carbon cathode is MFC. The power density only decreased by 12.7%, which was lower than that of the traditional Pt/C cathode MFC. After 6 months of operation, the surface of the active carbon cathode was completely covered by the biofilm, and the part of the pores in the catalytic layer were blocked by the biofilm, which resulted in the reduction of the cathode phase reaction interface and the mass transfer capacity of the electrode oxygen, thus inhibiting the catalytic activity of the cathode. With the surface biofilm and further removal of the inner membrane of the pores, the mass transfer capacity of the electrode oxygen is increased, the exchange current density is 8.6% and 34.5% respectively, the charge transfer internal resistance is reduced by 23.1% and 44% respectively, and the maximum power density of MFC is gradually restored. The active carbon loaded nano silver catalyst was synthesized and the hydrophilic catalytic layer modified by LA132 binder was synthesized. The high catalytic activity and good biological pollution effect were obtained. The maximum power density of MFC was increased by 150 days after the activated carbon was loaded with nano silver. A small amount of biofilm on the surface of 38.3%. electrode surface in the cathode surface biofilm is not only conducive to the transmission of oxygen in the cathode interface, but also alleviates the mass transfer resistance of the OH- from the catalytic layer to the main electrolyte, and the cathode overpotential is reduced. By adding the LA132 binder to the PTFE binder, the activated carbon is catalyzed. The hydrophilicity of the layer is increased gradually, which increases the wettability of the three-phase interface and promotes the mass transfer of the proton to the reaction site. When the ratio of LA132 is 67% in the composite binder, the maximum power density of MFC increases the hydrophilicity of 13.9%., while the modification of the LA132 binder also increases the surface electronegativity of the catalytic layer, thus effectively inhibiting the micro level. Biological adhesion and growth of biofilm. After 150 days of operation, the protein content in the cathode biofilm is only PTFE cathode 52.5%. using the prepared cathode to investigate the power production capacity of the cathode in the single chamber MFC with domestic sewage as the substrate. Compared with the PTFE cathode voltage (323 + 44 mV) and the power density (411 + 5 mW/m2), the composite binder cathode The higher output voltage is 398 + 15 mV and the power density is 454 + 24 mW/m2.. The removal rate of COD and TN in the effluent of the MFC reactor is 90.2 + 3.6% and 80.3 + 8.3%. respectively. The current density of MFC can be increased by reducing the external resistance, while the removal rate of COD and TN is increased.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TM911.45

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