HYDROGEN FUEL CELLS

Hydrogen fuel cells have three main elements :

• Electrodes (anode, where H₂ is reduced into two H+ protons and cathode, where H+ and O₂ protons react)

• Electrolyte (separates the gases, allows the passage of H+ ions to the cathode and separates the e-)

• Bipolar plates (that separate the cells, ‘conduct’ the gases and evacuate H₂O)

The reactions that take place at each of the electrodes are as follows:

• Reaction at the anode: H₂ –>2H+ + 2e-
• Reaction at the cathode: ½ O₂ + 2H+ + 2e- –> H₂O
• Global reaction: H₂ + ½ O₂ –> H₂O

On the anode side, the incoming hydrogen dissociates into protons and electrons. The protons are conducted through the membrane to the cathode, but the electrons are forced to travel through an external circuit (producing energy) as the membrane is electrically insulated. In the cathode catalyst, oxygen molecules react with electrons (conducted through the external circuit) and protons to form water. In this case, the only residue is water vapour or liquid water.