基于阳极生物膜分布调控的微流体微生物燃料电池传输机理及产电特性

发布时间：2018-07-31 07:22

【摘要】：微生物燃料电池(MFC)是一种利用细菌的代谢作用,高效处理污水中的有机物同时将其直接转化为电能的绿色能源技术。近年来,MFC的体积逐渐缩小到微纳级别,构成了微流体微生物燃料电池(MMFC),其作为一种产电设备和在线分析检测技术,在环境监测、生物分析以及微小电源技术方面具有广阔的应用和发展前景,是微流体能源技术的研究热点之一。现阶段的MMFC主要是对大型电池的按比例缩小,受到阳极侧生物膜分布有限、电池运行成本高昂、电池内阻大以及单位成本下产电功率密度低等问题的困扰;与此同时,电池中涉及到的流动和传输现象并未得到深入研究,特别是在流动条件下微小空间内生物膜的成膜特性尚未阐释清楚。针对以上生物膜分布有限和电池功率低下的问题,本文从工程热物理学科中的流体力学和传质理论出发,立足于微流道内阳极生物膜的分布调控,对MMFC内的传输机理和产电特性展开研究。研究内容主要包括:(1)构建了具有单阳极液入口的Y型MMFC,研究了阳极液浓度、阴极液浓度、反应液流量等运行参数对电池性能的影响,并对阳极侧沿流动方向的生物膜分布进行了观察;(2)构建了不同电池构型的MMFC,从缓解扩散混合区域影响的角度出发,构建了具有渐扩流道结构的MMFC,从生物膜分布、阳极侧内阻、电池产电性能等方面研究了改变流道结构对电池性能的影响;从减薄阳极侧边界层的角度出发,构建了具有多阳极液进口的MMFC,与单阳极液进口电池的产电性能进行了对比;通过控制旁路阳极液进口的开关状态分析了增加阳极进口对电池产电性能的作用机理;(3)构建了新型阳极电极和空气自呼吸式MMFC,基于产电菌附着强化思想,构建了一种基于氮掺杂石墨烯气凝胶的新型三维阳极材料,分别从材料化学和生物化学的角度对电极进行了表征,并从生物膜附着、阳极电荷迁移和电池产电方面进行了研究;基于流动简化思想,构建了一种单股流体控制下的空气自呼吸式微流体MFC,研究了所合成催化剂的物理化学特性和电催化特性,并分别在连续流和序批条件下进行电池性能测试。本文主要研究成果如下:1)构建了一种基于石墨电极的Y型结构MMFC,电池性能随着阳极入口燃料浓度和阳极液体积流量的增加而呈现先增加后下降的趋势;在入口燃料浓度化学需氧量为1500 mgL~(-1),阳极液流量为10 m L h-1时,输出的最大面积功率密度为618±4 m Wm~(-2）;对阳极侧表面生物膜形貌的观察发现:产电菌形成的生物膜厚度沿流动方向逐渐减薄,即:流体入口段的生物膜厚度要大于充分发展段的相应厚度;2)构建了基于渐扩、平行、渐缩的三种微流道结构的MMFC,渐扩通道成功避免了扩散混合区的影响,整体上拥有更致密的生物膜分布,同时基于渐扩通道的MMFC在阳极侧电荷迁移阻力最低,其产生的最大面积功率密度为2447.7±38.9m Wm~(-2）,是基于渐缩通道的MMFC的5.29倍(462.7±17.5 m Wm~(-2）)和基于平行通道的MMFC的1.24倍(1980.1±27.5 m Wm~(-2）);3)构建了基于多阳极液进口的MMFC(MMFC-MI),生物膜在微通道内沿流动方向整体呈致密分布,特别是在三个等间距分布的阳极液入口处,生物膜的分布远远大于单进口MMFC;电池在接种完成后旁路进口关闭状态下MMFC-MI的最大功率密度是打开状态下的85.6%,证实旁路进口的主要作用体现在产电菌富集阶段,而在接种完成后阳极液强化传输的作用相对有限;4)构建了一种基于石墨烯气凝胶(N-GA)的生物阳极材料,其三维结构和含氮官能团有利于强化产电菌在电极内外表面的附着;同时掺杂氮元素后降低了电子从生物膜表面向电极表面的迁移阻力;基于N-GA生物阳极的微型MFC所能达到的体积功率密度为225±12 Wm~(-3）(正比于腔室体积)和750±40 Wm~(-3）(正比于阳极体积);5)构建了一种单股流体控制下的空气自呼吸式MMFC,同时合成了一种含有丰富官能团的氮掺杂石墨烯气凝胶-活性炭(AC@N-GA)氧还原(ORR)催化剂;该催化剂展现了优良的ORR催化性能,电子转移数达到3.92,H_2O_2产率只有4.5%,以AC@N-GA为催化剂的MMFC连续流条件下最大功率密度为1181.4±135.6 Wm~(-3）,序批条件下最大功率密度为690.2±62.3 Wm~(-3）,产电性能是相同条件下国际报道MMFC的10倍以上。
[Abstract]:Microbial fuel cell (MFC) is a green energy technology which uses the metabolism of bacteria to efficiently deal with organic matter in sewage and directly convert it into electrical energy. In recent years, the volume of MFC has gradually reduced to the micro nano scale, which constitutes a microfluidic biofuel battery (MMFC). It is used as an electric equipment and on-line analysis and detection technique. Operation, in the field of environmental monitoring, bioanalysis and micro power supply, has a broad application and development prospect. It is one of the hot topics in the research of micro fluid energy technology. At the present stage, MMFC mainly reduces the proportion of large batteries, is limited by the distribution of the anode side biofilm, the high cost of the electric pool, the large battery internal resistance and the unit cost. At the same time, the flow and transmission phenomena involved in the battery have not been deeply studied. Especially, the film forming characteristics of the biofilm in the micro space under the flow condition have not been explained clearly. In view of the problems of the limited distribution of the biofilm and the low power of the electric pool, this paper from the Engineering Thermo Physics Based on the theory of fluid mechanics and mass transfer in the family, the transmission mechanism and production characteristics in MMFC are studied based on the distribution and regulation of the anode biofilm in the micro channel. The main contents are as follows: (1) the Y type MMFC with the inlet of the single anode liquid is constructed, and the operating parameters such as the concentration of anode liquid, the concentration of cathode liquid, the flow rate of the reaction liquid and so on are studied. The influence of pool performance was observed and the distribution of biofilm distribution along the direction of the anode side was observed. (2) the MMFC of different battery configurations was constructed. From the angle of alleviating the influence of the diffusion mixing region, the MMFC with the gradually diffused channel structure was constructed. The change of the channel junction was studied from the distribution of the biofilm, the internal resistance of the anode side, the battery production performance and so on. The effect of structure on the performance of the battery was constructed. From the angle of the boundary layer of the thin anode side, MMFC was constructed with the multi anode fluid inlet. The electric performance of the single anode liquid imported battery was compared. The mechanism of increasing the anode inlet on the battery production performance was analyzed by controlling the switch state of the anode liquid inlet. (3) a new method was constructed. A new type of three dimensional anode material based on nitrogen doped graphene aerogels was constructed based on the attachment and strengthening idea of a nitrogen doped graphene. The electrode was characterized from the material chemical and biochemical angles, and the electrode was attached to the biofilm, the anode charge migration and the battery production were studied. Based on the flow simplification idea, a kind of air self breathing micro fluid MFC under the control of single strand fluid was constructed. The physical and chemical properties and electrocatalytic properties of the synthesized catalyst were studied. The performance of the battery was tested under continuous and sequence batch conditions. The main results were as follows: 1) a type of Y type based on graphite electrode was constructed. With the increase of the fuel concentration of the anode inlet and the volume flow of the anode liquid, the performance of the cell MMFC increases first and then decreases. The maximum area power density of the output is 618 + 4 m Wm~ (-2) at the inlet fuel concentration of 1500 mgL~ (-1) and the anodic liquid flow rate of 10 m L H-1. It is found that the thickness of the biofilm formed by the producing bacteria gradually thins along the flow direction, that is, the thickness of the biofilm in the inlet section of the fluid is greater than the corresponding thickness of the full development section; 2) the MMFC based on the three microfluidic structures, which is based on the gradual expansion, parallel and shrinking, has successfully avoided the influence of the diffusion mixing zone and has a more compact overall. The biofilm distribution, at the same time, is the lowest resistance of MMFC based on the anodic side, the maximum area power density is 2447.7 + 38.9m Wm~ (-2), which is based on the 5.29 times of MMFC of the gradually shrinking channel (462.7 + 17.5 m Wm~ (-2)) and 1.24 times of MMFC (1980.1 + 27.5 m Wm~ (-2)) based on the parallel channel; 3) constructed based on the multi anode fluid. The imported MMFC (MMFC-MI), the biofilm is densely distributed along the flow direction in the microchannel, especially at the three equal spaced anodic fluid entrance, the distribution of the biofilm is far greater than that of the single import MMFC, and the maximum power density of the MMFC-MI is 85.6% under the closed state of the battery after the inoculation is completed. The main role of road inlet is reflected in the enrichment stage of producing electric bacteria, and the effect of enhanced transmission of anodic liquid after inoculation is relatively limited; 4) a biological anode material based on graphene aerogel (N-GA) is constructed. Its three-dimensional structure and nitrogen containing functional groups are beneficial to strengthen the attachment of electric bacteria to the inner and outer surfaces of the electrode; and doping nitrogen elements at the same time. The transfer resistance of electrons from the surface of the biofilm to the surface of the electrode was reduced; the volume power density of the micro MFC based on the N-GA bio anode was 225 + 12 Wm~ (-3) and 750 + 40 Wm~ (-3) (positive ratio to the anode volume); 5), a self breathing MMFC under the control of single strand fluid was constructed, and a synthetic one was synthesized at the same time. A nitrogen doped graphene aerogel - active carbon (AC@N-GA) oxygen reduction (ORR) catalyst, which contains rich functional groups, shows excellent ORR catalytic performance, the number of electron transfer is 3.92, the yield of H_2O_2 is only 4.5%, the maximum power density of MMFC continuous flow with AC@N-GA as catalyst is 1181.4 + 135.6 Wm~ (-3), under the precondition batch condition The maximum power density is 690.2 + 62.3 Wm~ (-3), and the electricity generation performance is 10 times higher than that of the international report MMFC under the same conditions.
【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TM911.45

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