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Fuel Cells. Presented By: -Taylor Morton -Chris Irvine. 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.
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Fuel Cells Presented By: -Taylor Morton -Chris Irvine
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
PEM(Proton Exchange Membrane) • A.K.A. Hydrogen Fuel Cell • Operating temp. = 80ºC • Requires electrocatalyst • Electrodes • Platinum based • Graphite • Sulfonated perfluroethylene
PEM continued • Anode: 2H2(g) ---> 4H+(aq) + 4e- • Cathode: O2(g) + 4H+(aq) + 4e- ----> 2H2O(g) • Overall: 2H2(g) + O2(g) ----> 2H2O(g) • Process • 2 H2 absorbed • 2 e- from each H2 travel externally • 2H+ hydrate and migrate • O2 absorbs e- • O2- receives H+ • H20 formed Source: http://physics.nist.gov/MajResFac/NIF/Images/FuelCellBasic.gif
Efficiency • No Pollutants • Other environmental impact • How is H2 obtained? • Viability • PEM = 75% • Coal-fired = 40% • Petroleum in ICE = 25%
Microbial Fuel Cells Using microorganisms to generate energy
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
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
It’s just science • mediator crosses the outer membrane • Accepts e- that would normally be taken up by O2 • e- laden mediator exits cell and transports e- to anode • after e- deposition, mediator returns to original oxidized state
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
C12H22O11 + 13H2O ---> 12CO2 + 48H+ + 48e- • The biofilm is attached to the anode • Anaerobic conditions force bacteria to respire anaerobically (duh)
Now what? • Waste Water Plants • Power stations based on plants/algae