Chemistry

Fuel cell types

Fuel cell types



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The alkaline fuel cell

Properties and structure

The alkaline fuel cell (English Alkaline Fuel Cell (AFC) is a low temperature fuel cell. It works in the temperature range of approx. 20 until 90° C and achieves efficiencies between 60 until 70%. The oxygen used as the oxidizing agent must also be very pure.

Potash lye (usually 30%) serves as the electrolyte in these cells. For example, platinum or Raney nickel is used as a catalyst in the graphite gas diffusion electrodes.

Reaction

2H2+4OH4H2O+4eAnode reactionO2+2H2O+4e4OHCathodic reaction2H2+O22H2OOverall response

Advantages and disadvantages

Advantages:

  • good efficiency
  • Use of inexpensive catalysts

Disadvantage:

  • Intolerance to carbon dioxide (CO2), since the potassium hydroxide crystallizes out of the potassium hydroxide otherwise to form insoluble carbonate. For this reason, the AFC can only be used with highly pure, i.e. CO2-free fuels are operated, i.e. pure water and oxygen. Because of its CO2Content cannot be used.

Applications

Military (e.g. submarine drives), on-board power supply for manned space shuttles