1.11 Electrode potentials and electrochemical cells

• Positive electrode reaction in a lithium cell

  Li+ + CoO2 + e- -> Li+[CoO2]-
• Negative electrode reaction in a lithium cell

  Li -> Li+ + e-
• Negative electrode reaction in an alkaline hydrogen-oxygen fuel cell


  H2(g) + 2OH-(aq) -> 2H2O(l) + 2e-
• Positive electrode reaction in an alkaline hydrogen-oxygen fuel cell


  1/2O2(g) + H2O + 2e- -> 2OH-(aq)
• Benefits of alkaline hydrogen-oxygen fuel cells

  • Hydrogen fuel cells only produce water.
• Risks of using alkaline hydrogen-oxygen fuel cells

  • Currently, almost all hydrogen is still produced by fossil fuels, and this is very environmentally damaging.
  • Hydrogen is explosive.
• Identify an ionic compound that could be used in the salt bridge.

  Potassium / sodium nitrate
• State why a fuel cell does not need to be electrically recharged.

  Reactants supplied continuously
• Suggest one advantage of using methanol, rather than hydrogen, in a fuel cell for use in cars.

  • More energy can be produced from 1cm3 of methanol than from 1cm3 of hydrogen
  • Methanol can be stored/ transported easily
• Explain how the salt bridge provides an electrical connection between the two solutions.

  ions can move through it