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研究发现微生物燃料电池从启动到稳定运行的过程中往往存在一种现象,就是在高电流密度下,微生物燃料电池的输出电压会出现逆转,从而限制了微生物燃料电池的规模化应用,以及它在污废水处理、脱盐等方面的功能.前期研究发现,微生物燃料电池的性能逆转现象与阳极材料的电容性能有关.电极材料的电容越大,越有利于微生物燃料电池的产电性能稳定,换言之,阳极材料电容不足导致产电性能逆转.但是超级电容活性炭的制作工艺繁琐,成本高,且导电性弱,不能满足微生物燃料电池的应用需求.炭黑的导电能力强、化学稳定性高、成本低,但作为微生物燃料电池的阳极则产生产电性能逆转现象.化学修饰(如酸、碱活化或者添加具有赝电容性质的金属氧化物等)可以提高材料的电容性能.低温条件(80℃)下,对低电容材料—炭黑进行HNO3和KOH的化学活化处理,并在此基础上,进一步用5%Fe3O4修饰,采用辊压工艺,以质量分数为60%的聚四氟乙烯乳液为粘结剂,制作微生物燃料电池的阳极,与空气阴极构建单室微生物燃料电池系统.采用傅里叶变换红外光谱(FTIR)、比表面积测试、材料表面pH和X射线能量分析光谱(EDX)等手段表征炭黑活化前后的物理、化学性质;接触角润湿性测试表征活化前后电极表面的亲疏水性.电化学循环伏安法测试活化前后,电极的电子存储能力.与蒸馏水的p H相比较,材料表面pH分析表明炭黑材料经化学活化处理后,其表面pH无明显变化;FTIR和EDX测试表明化学活化处理使得炭黑表面引入含O(N)官能团;吸附-脱附曲线分析表明化学活化后,炭黑的比表面积减小,微孔与介孔的体积比增加;接触角测试表明炭黑阳极活化处理后,电极表面亲水性增加;循环伏安测试证实,化学活化后的炭黑阳极电容得到0.1–0.8F/cm2的增长.结合燃料电池的产电性能测试,发现只有当炭黑阳极电容不小于1.1 F/cm2时,微生物燃料电池的产电逆转现象才会消失.炭黑阳极的化学活化方法为微生物燃料电池的性能稳定提供了一种简便、低成本的方法.
It is found that there is often a phenomenon in the process from start-up to stable operation of microbial fuel cells, that is, the output voltage of microbial fuel cells will reverse at high current density, thus limiting the scale application of microbial fuel cells, Wastewater treatment, desalination and other functions.Previous studies found that microbial fuel cell performance reversal phenomenon and anode material capacitance performance.Electrode material capacitance, the more conducive to the microbial fuel cell power generation performance and stability, in other words, However, the manufacturing process of supercapacitor activated carbon is cumbersome, high cost and weak in conductivity, and can not meet the application requirements of microbial fuel cells.The carbon black has high conductivity, high chemical stability and low cost , But as the anodes of microbial fuel cells produce electricity reversal phenomenon.Chemical modification (such as acid, alkali activation or the addition of metal oxide with pseudocapacitance, etc.) can improve the capacitive properties of the material.Low temperature conditions (80 ℃) , The low-capacitance material - carbon black HNO3 and KOH chemical activation treatment, and in this base , And further modified with 5% Fe3O4, using a roll process, a polytetrafluoroethylene emulsion with a mass fraction of 60% as a binder to make an anode of a microbial fuel cell and an air cathode to construct a single-chamber microbial fuel cell system. Fourier transform infrared spectroscopy (FTIR), specific surface area test, surface pH and energy dispersive X-ray spectroscopy (EDX) were used to characterize the physical and chemical properties of carbon black before and after activation. The contact angle wettability test . The electrochemical storage capacity of the electrode before and after activation was measured by electrochemical cyclic voltammetry.Compared with the p H of distilled water, pH analysis of the surface of the material showed that there was no significant change in the surface pH of the carbon black after chemical activation treatment. FTIR And EDX tests showed that the chemical activation treatment led to the introduction of O (N) functional groups on the surface of carbon black. The adsorption-desorption curve analysis showed that the specific surface area of carbon black decreased and the volume ratio of micropore to mesopore increased after chemical activation. The test showed that the hydrophilicity of the electrode surface increased after activation of the carbon black anode, and the cyclic voltammetry test confirmed that the carbon black anode capacitance after chemical activation was increased by 0.1-0.8 F / cm2. Battery production performance test and found that only when the carbon black anode capacitance of not less than 1.1 F / cm2, microbial fuel cell power generation reversal phenomenon will disappear.The chemical activation of carbon black anode for microbial fuel cell performance and stability provided A simple, low-cost method.