Study On The Electrode Materials To Improve The Performances Of Microbial Fuel Cells

In recent years, as one of constraints for human survival and development, the energy crisis and environmental problems such as water pollution have become increasingly prominent. It will be the best choice if the energy that exists in the form of biodegradable organic matter is recovered during wastewater treatment. Microbial fuel cells (MFC) are novel processes that use bacteria as the catalysts to oxidize organic matter and directly convert chemical energy into electricity. It has been used for wastewater treatment to achieve the above purpose, but it is still in laboratory research because of the low output power.Among the many factors, the electrode material especially for anode material has been regarded as an important factor on the performance and costs of MFC. In addition to excellent anode materials selection, the anode modification is one of the effective methods. However, most of the existing anode modification methods have some problems with complex equipment, harsh conditions, long preparation time and poor practical application ability. Therefore, in the present work, two simple anode material modified methods based by electrochemical treatment were studied in air-cathode single chamber reactor to improve the performances of MFC.Firstly, we used low-cost carbon mesh as anode materials. Electrochemical oxidation method (10 mA,30 min) was selected to modify these anode surface with HNO3, NH4NO3 and (NH4)2S2O8 as the electrolyte separately. Then corresponding MFCs were started and investigated. The main conclusions were as follows:1. The maximum power density of the MFC with the anode modified by nitric acid was 792 mW/m2, which was 43% larger than the unmodified control (552 mW/m2). The one after ammonium nitrate treatment increased by 33% to 736 mW/m2.2. It was noteworthy that after anode modification the internal resistance of CM-N and CM-A MFC was reduced to 122Ωand 125Ω, which was 23% and 21% lower than the unmodified one (158Ω), respectively.3. It showed that modification improved the surface roughness and the ratio of N1s/C1s by SEM, XPS. These changes improved the current response and reduced the anodic potential, which might be the reasons and mechanism of the modification.4. Compared with the previous anode modified methods, the electrochemical method advantaged over low cost, moderate operating conditions and more suitable for engineering application.Secondly, we also studied the graphite felt modification by nano-polypyrrole that developed by electric polymerization reaction using different cyclic voltammetry, e.g.,5CV (PPy-1),10CV (PPy-2) and 20CV (PPy-3). The influences of reaction time on the morphology of polypyrrole and on the performances of MFC were investigated. The experiment results showed the dimension of polypyrrole was about 50nm. The polypyrrole film increased with reaction time, and the prepared nanoparticles stacked group then. The power density of the unmodified was 375 mW/m2. The maximum power density of PPy-2 reactor was 430 mW/m2, which increased by 15% compared with the control. At the same time, the maximum power density of PPy-3 increased to 412 mW/m2. In addition, the coulombic efficiency and COD removal were also increased after modification.