GCSE Chemistry (AQA)

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Fuel Cell Half Equations

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Energy changes Chemical cells and fuel cells

Fuel Cell Half Equations

2:44 Reactions at Electrodes in Hydrogen Fuel Cells
Spec 4.5.2.2
Previous Fuel Cells Next Relative Formula Mass
  • Hydrogen and oxygen react in a hydrogen fuel cell to form water as the only product.
  • Hydrogen gas is pumped in one end, and oxygen gas is pumped in the other.
  • The reaction generates a potential difference and produces water, which is pumped out.
  • Leftover hydrogen is pumped out and can be recycled back into the cell.
  • The chemical equation for the reaction is 2H2 (gas) + O2 (gas) ��� 2H2O (liquid).
  • The reaction at each electrode can be written as a half equation.
  • At the negative electrode: 2H2 ��� 4H+ + 4e-.
  • At the positive electrode: O2 + 4H+ + 4e- ��� 2H2O.
  • The two half equations can be combined into one large equation.
  • The overall equation for the reaction is 2H2 + O2 ��� 2H2O.
  • This equation is the same as for the combustion of hydrogen, but achieved through different means.

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