Studies On Iron/manganese Modified Electrodes And Current-producing Properties In Benthonic Microbial Fuel Cells

In the 21st century, energy shortage and environmental pollution are two critical problems in people's livelihood and sustainable development of the national economy. Microbial fuel cell is a new non-polluting energy technology, which not only eases the energy crisis and the greenhouse effect produced by traditional energy sources, but also handles a variety of waste generated in life and production. Thus, great research value and development space exist in this area. Benthonic microbial fuel cell (BMFC) is a special kind of MFC. The anode is buried in the anaerobic marine sediments, and connected with the cathode in the seawater through the external circuit. The metabolism of microbes oxidizes the organic matter in the sediments, while produces current. BMFC is a very promising driver to work for the low-power monitoring instruments in the remote sea area.At present, BMFC has not been widely used. The key issue is the low output power density. The most critical limiting factor is the electron transport rate between the microbe and the anode and between the cathode and the oxygen. Therefore, for improving the electron transport rate, modifying the anode and the cathode is an important way. General requirements about the anode are high conductivity, small internal resistance, stable anodic potential, chemical stability and good biocompatibility. High-performance anode favors the growth of the microbial attachment and facilitates the electron transfer from the microbial body to the anode; High-performance cathode helps improving oxygen-reducing rate on its surface.To improve the BMFC's output power density, we respectively used the electron-mediators MnSO4 and Fe3O4 to modify the graphite anode; we used catalyst MnO2 to modify the graphite cathode. We carefully studied the effect of these three substances'content on the electrode and the electrical properties of the BMFC. As a result, when the content of MnSO4 and Fe3O4 in the graphite anode were respectively 4% and 2%, the anode exhibits the best performance with smallest battery internal resistance and highest output power density (51.64 mW/m2 and 47.97 mW/m2), about 3 times the values of the pure graphite anode; when the content of MnO2 in the graphite cathode was 4%, the cathode behaves the best performance with smallest internal resistance, highest output power density(20.10m W/m2), over 2 times the value of the pure graphite cathode. At last, we respectively added 4% MnSO4 and 4% MnO2 into the graphite anode and cathode, and made a BMFC. The maximal output power density was greatly improved, about 5 times the unmodified BMFC.