4.3  How A Fuel Cell Works

• A fuel cell works on the principle that when hydrogen and oxygen atoms come together the hydrogen atoms release protons and electrons.
  
  
• Hydrogen, the energy source, is fed to one side of the fuel cell (“the anode”) and oxygen, which the hydrogen reacts with, is fed to the other side (“the cathode”).
  
  
• A membrane or ceramic electrolyte designed to allow the protons, but not the electrons, to pass through it from the hydrogen to the oxygen side, is located in the middle of the fuel cell.
  
  
• The electrons released by the hydrogen are made to flow via an external electrical circuit to reach the oxygen side of the fuel cell and by doing so create the required electrical current.
  
  
• When the protons and electrons combine at the oxygen side of the fuel cell water is produced and expelled from the fuel cell.
  
  
• Note: Fuel cells are used in NASA’s space shuttle and the expelled water is used for drinking.
  
  
• A fuel cell typically produces about 0.7 volts. To create sufficient voltage and current they are assembled together in a “stack”.