Fuel Cells, Edexcel Unit 5, A2

Notes on Hydrogen Fuel Cells, Alcohol Fuel Cells and Breathalysers

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  • Created on: 12-04-12 08:42
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Fuel Cells
Fuel Cells generate electricity by reacting a fuel with an oxidant. Often this is reacting
hydrogen with oxygen.
1) Platinum catalyses the breakdown of hydrogen into electrons and protons at the
2) A polymer electrolyte membrane (PEM) separating the anode and cathode only
allows H+ ions across it. This forces the electrons to travel around the circuit to get to
the cathode
3) The movement of the electrons through the circuit generates the electric
4) At the cathode the H+ and the electrons combine with oxygen (the oxidant) to
form water, the only waste product
5) Unreacted hydrogen is collected and can be reused
This method of producing energy is far less polluting as water is the only waste
product. However most hydrogen is made from reacting natural gas with steam or
by electrolysing water, both of which use huge amounts of energy and fossil
fuels. So the method is only as green as the method by which it is produced. A fuel cell
like this is also at least twice as efficient at converting fuel to power as a petrol
Fuel Cells Don't Have To Use Hydrogen
Fuel cells are being developed that can use other hydrogen rich compounds such as
methanol and ethanol. The advantages of these are:
1. They have a higher hydrogen density that liquid hydrogen ­ More hydrogen
atoms per unit volume
2. They are already made on a large scale using renewable biomass

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Methanol and Ethanol are far easier and safer to store and transport that
Hydrogen (when in liquid or gas state)
4. Methanol can be made from carbon dioxide so may offer a way to reduce
carbon dioxide in the atmosphere
Some new generation fuel cells can use alcohols directly the alcohol is oxidised at
the anode with water. The H+ ions then pass through the electrolyte and are oxidised
themselves to water. e.g.…read more


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