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Chemical Cells and Fuels Cells
Chemical cells use chemical reactions to convert and transfer energy to electrical energy. They will produce a voltage only up until one of the reactants has been used up (we say the battery has "gone flat").
Batteries, like the ones in torches and mobile phones, are made up of chemical cells. There are many types of chemical cell, each with different chemical reactions.
Fuel cells will produce a voltage continuously, provided they have a constant supply of fuel and oxygen (from the air).
Hydrogen-oxygen fuel cells
In this type of fuel cell, hydrogen and oxygen are used to produce a voltage. The only product from this reaction is water.
hydrogen + oxygen → water
2H₂ + O₂ → 2H₂O
Higher Only
At the anode: O₂(g) + 4H+(aq) + 4e- → 2H₂O(l)
At the cathode: 2H₂(g) → 4H+(aq) + 4e-
Uses of Fuel Cells
Hydrogen, diesel and petrol are all highly flammable fuels. Fuel cells have their advantages and disadvantages depending on the use.
Fuel cells in spacecraft
Advantages:
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no moving parts to maintain
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small in size for the amount of electricity produced
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water they produce can be used for drinking water
Disadvantages:
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they have to be continuously supplied with oxygen and hydrogen
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although this could be rectified by using solar cells to electrolyse the water produced back into oxygen and hydrogen
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Fuel cells in vehicles
Advantages:
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quiet in use
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water is the only waste
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fewer moving parts
Disadvantages:
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hydrogen is difficult to store
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not many places to fill up with hydrogen fuel
Petrol/Diesel in vehicles
Advantages:
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easier to store
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a lot more places to fill up with fuel
Disadvantages:
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noisy during use
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carbon dioxide is a waste product
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many moving parts