Polymer Fuel Cells

8/6/2019 Polymer Fuel Cells

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Onashan Pillay 207500797


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What is a fuel cell?

Electrochemical cell, exploiting chemical

reaction to produce electrical energy

Fuel is hydrogen and oxygen, in this

case


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Types of fuel cells

Polymer electrolyte membrane or proton

exchange membrane (PEM)

Solid oxide (SOFC)

Molten carbonate (MCFC)

Direct-methanol fuel cell (DMFC)


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How does it work?


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Cell Details

H2 dissociates under presence of Ptcatalyst

Operates between 50C 120C

50% - 70% efficiency

Membrane does not allow H2 and O2 topass


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Cell Details

Pt nanoparticles coated onto carbon paper

(catalyst)

Pt coated side of catalyst faces membrane

Polymer electrolyte looks like cling wrap

Cells generate about 0.7 volts but can be

combined to achieve desired output


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Ionomer

Polymer is specifically an ionomer

Ionomers unique in that they are electrical

conducting polymers

Repeated units of electrically neutral unitsand portion of ionized units

Nafion, a specific type of ionomer, is mostpopular


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Nafion

Made from copolymerization of Teflonmonomer and alkyl vinyl ether withsulfonyl acid fluoride

Conducts cations extremely well

Mechanically and thermally stable

Extruded into thin films


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Relating to Coal Tech & Gas

Coal reserves are diminishing fast

Investigated as alternative to burning coal

Several advantages over coal burning

Can be compared to/measured against

current ways of generating electricity

H2 is from steam reforming mainly with HC


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Advantages

Low operating T; cell warms up quickand thus supplies electricity soon afterstartup

Low T means more reliability (High T inSOFC, cell breaks down)

DMFC less efficient, more expensivethan PEMFC


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Advantages

No emissions

No moving parts to decrease efficiency

Water is a byproduct

SAwill run out of coal eventually, eco-

friendly alternative


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Disadvantages

Stacked fuel cells use bipolar plates toconnect to each other

Metallic plates corrode, with byproductsdecreasing cell efficiency

Composites, light metals and graphiteplates can be used for low-temperatureFCs


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Disadvantages

SOFC & MCFC generates steam from

high T. Can be used in turbines

PEMFC are expensive (Pt catalyst,

bipolar plates)

Durability decreases with cycling


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Disadvantages

For membrane to function, water

management is crucial

Near upper limiting T, membrane loses

water and cannot take in cations


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Applications

Can be used as power source almost

anywhere

Transport is the major research area

since PEMFC cleaner, compact

Conventional cars known to have

efficiencies from 20%- 40%


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Applications

PEMFC alone has 50% - 70% efficiency

But considerH

2 must be produced atsome efficiency at some plant

Efficiency decreases sharply to below

48%


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Applications

PEMFC needs continuous flow of fuel

How practical & safe is this in a vehicle?

Onboard storage ofH2 being

investigated


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References

Nice, Karim, and Jonathan Strickland. "How Fuel CellsWork" 18 September 2000. HowStuffWorks.com. 13 March 2011

Amanda Meyer, Reaction Engineering of PolymerElectrolyte Membrane Fuel Cells, 25August 2004

http://en.wikipedia.org/wiki/

Elizabeth S.H

oward, The Design of Optimal MaterialCombinations for the Membrane ElectrodeAssembly of aProton Exchange Membrane Fuel Cell, May 2006,Princeton

Documents

Polymer Fuel Cells