Download Microbial Fuel Cells

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
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Source: http://www.aerospaceweb.org/question/propulsion/jet/combustion.gif
PEM
(Proton Exchange Membrane)
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•
A.K.A. Hydrogen Fuel Cell
Operating temp. = 80ºC
Requires electrocatalyst
Electrodes
– Platinum based
– Graphite
– Sulfonated perfluroethylene
PEM continued
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Anode: 2H2(g) ---> 4H+(aq) + 4eCathode: O2(g) + 4H+(aq) + 4e- ---->
2H2O(g)
Overall: 2H2(g) + O2(g) ----> 2H2O(g)
Process
1.
2.
3.
4.
5.
6.
2 H2 absorbed
2 e- from each H2 travel externally
2H+ hydrate and migrate
O2 absorbs eO2- receives H+
H20 formed
Source: http://physics.nist.gov/MajResFac/NIF/Images/FuelCellBasic.gif
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
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 eto 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