A microbial fuel cell using biomineralized manganese oxides as a cathodic reactant
Rhoads, Allison Nicole
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Microbial fuel cells were designed and operated utilizing microorganisms in both the anodic and cathodic compartments. In the cathodic compartment we used Leptothrix discophora because of the microorganism's capability to deposit biomineralized manganese oxides on the electrode. Biomineralized manganese oxides are superior to oxygen when used as a cathodic reactant. In the anodic compartment of most of the fuel cells we oxidized glucose using Klebsiella pneumoniae. In one fuel cell we used Desulfovibrio desulfuricans, a sulfate reducing bacteria. Electrons released in the anodic compartment, from the oxidation of glucose or sulfide, were then used in the cathodic compartment to reduce microbially deposited manganese oxides. A redox mediator, 2-hydroxy- 1,4-napthoquinone (HNQ) was used in the anodic compartment to facilitate electron transfer from the microorganism to the electrode. The fuel cells with glucose oxidizing bacteria were operated for 500 hours and reached an average anodic potential of -441±31 mVSCE and an average cathodic potential of +384±62mVSCE. The fuel cells with sulfate reducing bacteria were operated for 136 hours and reached an average anodic potential of -470±44 mVSCE and an average cathodic potential of +419±59 mVSCE. Reticulated vitreous carbon or 316L stainless steel was used as the electrode material. The electrode materials did not have a significant effect on the potential of the fuel cell system. The average fuel cell potential for 316L stainless steel was 706.13±22mV and 759.75±73mV for reticulated vitreous carbon. When the fuel cells reached steady state we discharged them through a 510. resistor and evaluated the available power.