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    Add as Friendmicrobial fuel cell

    by: pushpak

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    2 : Use of the fossil fuels can trigger global energy crisis & increased global warming hence there is considerable interest in research fraternity on green energy production. MFC converts chemical energy to electrical energy by catalytic reaction of microorganisms. Electrons produced by metabolism of microorganisms are utilized for generation of electricity. MFC operates at near about ambient temperature & nearly neutral solutions. They operate on complex substrate present in waste water. MICROBIAL FUEL CELL
    3 : Principle is based on redox reaction between replenishable agents. Consists of anode, cathode, PEM or Salt bridge. Anode at anaerobic conditions & cathode at aerobic. PEM joining two chambers allows only protons to diffuse. Principle
    4 : At anode microbes oxidize substrate to CO2. Released electrons absorbed by anode & transported to cathode by electric circuit. The released protons diffuse through PEM & form water by combining with Oxygen. Anodic Reaction CH3COO + 2H2O -------- ? 2CO2 + 7H+ + 8e – or C6H12O6 + 6H2O 6CO2 -------- ? 24H+ + 24e- Cathodic Reaction O2 + 4H+ + 4e- -------- ? 2H2O or 24H+ + 24e- -------- ? 6O2 12H2O Working
    5 : Two compartment MFC Typically run in Batch Mode in medium like Glucose or Acetate to generate electricity. Currently used in laboratories only. Exists in various shapes like cylindrical, rectangular, miniature, Upflow with cylindrical, U-shaped cathode. Difficult to scale up due to their complex design. Designs of MFC
    6 : Two compartments MFC power output
    7 : Single compartment MFC Operate either in batch or continuous mode. Possess only an anodic chamber. Eliminates the need for cathodic chamber by exposing the cathode directly to air. Protons are transferred from the analytic solution to the air exposed cathode. Critical for practical implementation of MFC. Designs of MFC
    8 : Single compartment MFC power output
    9 : Types of MFC
    10 : Limit on surface area of anode as bacteria can clog small pores and hence limit on current. Still not economically competitive. Power produced way below when compared with conventional cells. The practical value of maximum voltage achieved is very low when compared to the theoretical value This can be attributed to Activation losses. Bacterial metabolic losses. Concentration losses. Limitations of MFCs
    11 : Non conductive lipid membrane, lipopoly saccharides & peptididoglycans in microbes hinder electron transfer to anode. Hence they require mediator for transport of electrons. Mediator in oxidizing state reduces by capturing electrons & transports it to anode & reoxidises. Synthetic mediators : Thionine, Methylene Blue, Neutral Red. Natural mediators : Anthraquione, Humic acid, Sulphate & Thiosulphate. Performance Enhancement of MFC Mediator Microbial Fuel Cell
    12 : Uses bioelectrochemically active bacteria to transfer electrons to electrode. They have electrochemically active redox enzymes like cytochromes on outer membrane that helps in electron transfer. Form a biofilm on the anode surface & transfer electrons directly by conductance to anode. Shewanella Putrefaciens & Aeromonas Hydrophila are some examples of bioelectrochemically active bacteria used. Performance Enhancement of MFC Mediator less MFC
    13 : Various Microbes used in MFCs
    14 : Modifying the anodes of a MFC using nanofabrication techniques can result in increase of the current density output of the MFC. Characterizing the Nanomodified anodes using microscopy can result in increase in efficiency of MFCs. Growing gold, iron, and nickel Nanoparticles (NPs) and Multi Walled Carbon Nanotubes(MWCNTs) on anode plate will increase the attracting power of anode towards electrons and hence will result in increase in efficiency of MFC. Carbon nanotubes Performance Enhancement of MFC Nanomodification of Anode Nanoscale: 1x 10-9m = 1nm. A hair is ˜ 10 µm (10,000 larger) Nanostructures are thought to improve e- transfer from bacteria to Anode.

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