Fuel cells Flashcards
what do we react in a fuel cell?
reacts fuel such as hydrogen with either pure oxygen or air
2 simple gases to produce electricity
what takes place and is produced in a fuel cell?
a chemical reaction takes place and an electric current is produced
in the hydrogen fuel cell, what is the only ones caught up with?
water
what happens in a negative electrode in a reaction between hydrogen and oxygen?
the hydrogen molecules split into hydrogen ions and electrons
the half equation for the negative electrode:
2H2 —> 4H+ + 4e-
in a positive electrode, what happens in the reaction in a fuel cell between hydrogen and oxygen?
what is the overall equation for the hydrogen fuel cell
the oxygen molecules now combined with the electrons and the hydrogen ions produced to the negative electrode
O2+4H+ + 4e- —> 2H2O
the hydrogen is being oxidised
hydrogen fuel cell overall equation:
2H2 + O2 —> 2H2O
what are the advantages to hydrogen fuel cells compared to rechargeable battery?
advantages:
- hydrogen fuel cells will produce electricity for as long as you provide hydrogen whereas rechargeable batteries run out and need to be recharged
- hydrogen fuel cells don’t get less efficient the longer they run whereas rechargeable batteries can store less electricity the more charging cycles they go through and eventually need to be replaced
- hydrogen fuel cells can be used as a source of drinkable water (eg on a space craft)
what are the disadvantages to hydrogen fuel cells compared to rechargeable battery?
disadvantages:
-hydrogen fuel cells run on hydrogen which is an explosive gas and is very difficult to store safely whereas no dangerous fuels are required with rechargeable batteries.
however, Some types of rechargeable batteries can catch fire if not manufactured correctly
-hydrogen fuel cells produce a relatively low pd /voltage so several are needed together whereas rechargeable batteries can produce a greater difference than a hydrogen fuel cell
