| Energy shortage and environmental pollution are two major challengs facing the world today, looking for renewable energy is an inevitable choice to solve the problem. Microbial fuel cells (MFCs) are bioreactors which use microbial to degrade waste and other organic matter, generating electrical energy. Due to the advantage of wide source of raw materials, pollution-free, low cost, the MFC has good application prospect. Benthic microbial fuel cell (BMFC) is a new type of the MFC, as its anode is embedded in sediment, the cathode in seawater. Microbial communities in sediment generating electrons from the anode pass to the cathode through an external circuit, and oxygen occurs reduction reaction with H+ at the cathode, forming a circuit current. Seabed sediment is rich in organic matter, the oxygen dissolved in seawater is constantly supplemented and updated, so the BMFC can provide a sustainable supply for low-power marine exploration equipments.But the low output power of the BMFC limits its practical application, anode is an important factor to limit output power. Anode modification can significantly improve the cell output power, therefore we use of polypyrrole/carbon nanotube composite and manganese/polypyrrole composite materials as anodes on the BMFC. From electrode polarization, capacitors, electron transferring and other aspect explore the factors, which effect BMFC output power and other electrochemical properties. The main research contents and conclusions are as follows:(1) Polypyrrole/multi-walled carbon nanotubes(PPy/MWCNTs) composite is synthesized by using SDBS as dopant, FeCl3·6H2O as oxidant via chemical oxidative polymerization method and the composite material is utilized to modify the anode in marine sediment microbial fuel cell, and test the electrochemical properties of the modified anode cells. Research result reveals that MWCNTs is tightly coated by polypyrrole and its maximum exchange current density is 0.66 mA/cm2,3.6 times more than the unmodified. PPy/MWCNTs anode contact angle decrease to about 60° more hydrophilic being beneficial to bacterial adhesion. The power density of modified cell reaches 408.8 mW/m2,5 times higher than the battery unmodified, which significantly improves the overall performance of the cell. Cyclic voltammetry shows that the modified electrode capacitance is a synergistic result of pseudocapacitive and electric double layer, which greatly improves electrons transfer efficiency and its anti-polarization capability. We presents a new electron transfer mechanism in the interface between the modified anode and biofilm.(2) MnO2/PPy composite is synthesized by in situ chemical polymerization, using MnSO4·H2O and pyrrole as the main raw material, KMnO4 and FeCl3·6H2O as the oxidant. Surface topography and properties are characterized by scanning electron microscopy and infrared spectroscopy, and their result shows that MnO2/PPy composite is a fluid structure. Cyclic voltammetry and linear sweep voltammetry test indicate that MnO2/PPy composite has a typical capacitance feature, capacitance increases 3.1 times more than the unmodified electrode,2.5 times of the PPy electrode. Anode contact angle of modified composite is reduced to 46 °, the cell internal resistance decrease to 420 Ω, reduce the electron transfer resistance. Electrochemical test of electrodes and cells suggest that the maximum power density of MnO2/PPy modified cell reaches 592.7 mW/m2,2.2-fold than unmodified cell. Surmises the synthesis mechanism of MnO2/PPy, and analyzes the impact of composite materials on BMFC. |
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