1. Fuel Cells Presented By: -Taylor Morton -Chris Irvine

2. Overview Not self contained Reactants enter cell Products leave cell Use combustion to produce electricity E - transferred through external circuit Source: http://www.aerospaceweb.org/question/propulsion/jet/combustion.gif

3. PEM (Proton Exchange Membrane) A.K.A. Hydrogen Fuel Cell Operating temp. = 80ºC Requires electrocatalyst Electrodes –Platinum based –Graphite –Sulfonated perfluroethylene

4. PEM continued Anode: 2H 2 (g) ---> 4H + (aq) + 4e - Cathode: O 2 (g) + 4H + (aq) + 4e - ----> 2H 2 O(g) Overall: 2H 2 (g) + O 2 (g) ----> 2H 2 O(g) Process 1.2 H 2 absorbed 2.2 e - from each H 2 travel externally 3.2H + hydrate and migrate 4.O 2 absorbs e - 5.O 2 - receives H + 6.H 2 0 formed Source: http://physics.nist.gov/MajResFac/NIF/Images/FuelCellBasic.gif

5. Efficiency No Pollutants Other environmental impact –How is H 2 obtained? Viability –PEM = 75% –Coal-fired = 40% –Petroleum in ICE = 25%

6. Microbial Fuel Cells Using microorganisms to generate energy

7. What it is! Converts chemical energy to electrical energy by the catalytic reaction of microorganisms Exact same principle as a voltaic cell, only using the respiration of bacteria to generate electricity

8. Mediated Methylene Blue, thionine, or humic acid –Mediator acts as electrolyte –Facilitates e - transfer from microbial cells to the electrode –Mediator is necessary because most microbes are electrochemically inactive

9. It’s just science mediator crosses the outer membrane Accepts e - that would normally be taken up by O 2 e - laden mediator exits cell and transports e - to anode after e - deposition, mediator returns to original oxidized state

10. Mediator-less: S. putrefaciens Electrochemically active bacteria usually have cytochromes (or other redox enzyme) in their outer membranes that can transfer e - e - are carried directly to the anode

12. C 12 H 22 O 11 + 13H 2 O ---> 12CO 2 + 48H + + 48e - The biofilm is attached to the anode Anaerobic conditions force bacteria to respire anaerobically (duh)

13. Now what? Waste Water Plants Power stations based on plants/algae