Learning outcomes

After studying this topic you should be able to:

Understand:

• Electrochemical cells have internal resistance because of the finite time it takes for ions to diffuse.
• The internal resistance of a cell limits the current it can produce.
• The voltage of a battery primarily depends on the type of materials used, while the total work output depends on their quantity.
• In primary cells the electrochemical reaction is non-reversible. Rechargeable cells involve redox reactions that can be reversed using electricity.
• Fuel cells convert the chemical energy that is contained in the consumed fuels directly into electrical energy.
• Microbial fuel cells, MFCs, which use different carbohydrates or substrates present in waste waters as the fuel, are a possible sustainable energy source.
• The potential of a half-cell under non-standard conditions can be calculated from the Nernst equation:
  
• Concentration cells contain the same electrodes but the concentration of the electrolyte solutions at the cathode and anode are different.

• Distinguish between fuel cells and primary cells.
• Deduce the half equations for the electrode reactions in a fuel cell.
• Compare fuel cells with rechargeable batteries.
• Discuss the advantages of different types of cells in terms of size, mass and voltage.
• Solve problems using the Nernst equation.
• Calculate the thermodynamic efficiency (ΔG/ΔH) of a fuel cell.
• Explain the workings of rechargeable batteries and fuel cells (including diagrams and relevant half-equations).

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