Fuel Cells

Presented By:

-Taylor Morton

-Chris Irvine

Overview

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

• 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

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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