Application Of Carbon Materials In Benthonic Sediment Microbial Fuel Cells

Energy shortage and environmental pollution limits the sustainable development of human beings. Microbial fuel cells (MFCs) are bioreactors which convert chemical energy in the chemical bonds in organic compounds into electrical energy through catalytic reaction of microorganisms under anaerobic conditions. Benthic Sediment microbial fuel cells (BMFCs) generate electricity from oxic seawater and anoxic sediments. In general, a BMFC consists of an anode, buried under marine sediment, and connected by an electrical circuit to the cathode, immersed in seawater. Electrons are delivered to the anode by microorganisms from organic matter degradation. BMFCs can supply electric power for small marine instruments.Enhancing electrode performance and reducing its cost are of great significance to scale up BMFCs for practical application.In this paper, the effect of different carbon anode materials on BMFCs performance was studied. An explorative study on bio-degrading pollutants in marine sediment by BMFCs was also shown Main results are as follows:(1) When rayon-based carbon fiber, PAN carbon fiber, carbon brush, carbon fiber felt, foamy carbon, carbon rod and carbon plate were used as BMFCs’anodes and cathodes respectively, their particular surface structures affected the mass transfer rate and the internal resistance of cell,and owned different electricity generation performances. The rayon-based carbon fiber which showed a high polarization resistance ability and output power density was suitable for practical application in marine species.(2) To enhance performance of anode, the carbon fiber was modified by a unique electrochemical treatment. Results showed that the contact angle of the anode was decreased from142°to52°due to the introduction of hydrophilic functional groups after the modification. The current density and anti-polarization ability of the modified anode were significantly higher than the plain anode at the same potential. The maximum power density of the BMFCs with modified anode reached673.2mW/m2, about2.4times higher than unmodified cell (285.1mW/m2). These indicated that the adopted treatment provided a new perspective to enhance power generation that can maximize BMFCs energy generation and system large-scale construction.(3) To develop a high-performance and low-cost BMFC anode, manganese oxide (MnO2)/multiwall carbon nanotubes (MWCNTs) nanocomposites were prepared via a direct redox reaction between permanganate ions (MnO4) and MWCNTs and then used as anode materials. Results showed that the MnO2/MWCNTs anodes had a better wettability and greater kinetic activity than the plain graphite anode. The BMFCs with a MnO2(50%)/MWCNTs anode delivered a maximum power density of109.1mW/m2and a stable current of1.2mA, which were much higher than that with a plain graphite anode (9.2mW/m2,0.3mA). The percentage of MnO2in the resulting MnO2/MWCNTs samples had a strong influence on the anodes performance.(4) An in-situ bio-remediation of marine sediment pollution using BMFCs was also tested. The results indicated that BMFCs had a promoting effect on degrading marine sediment pollution. The degradation rate of organic pollutants was significant positively correlated with the generation of electricity. The research provide a new way of sludge recycling and monitoring. In this part, a mechanism of the electro-catalytic degradation of organic carbon was proposed for the illustration of in-situ bio-remediation using BMFCs.