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Proton Exchange Membrane Fuel Cells (PEMFC) are most likely to become capable of substituting for the presently used diesel and petrol engines in the future. This type of cells was first used by NASA used in the GEMINI program during the 1960’s. The material of the electrode in these cells is a solid polymer membrane (a thin plastic film layer). This polymer has the important property that in wet state it lets through the protons, however, it is not permeable for the electrons.

On the anode the flowing in hydrogen splits into protons and electrons. The protons move towards the cathode through the membrane, while the electrons reach it through an outer circuit, producing electric energy in the meantime. The electrons arriving at the cathode combine with the oxygen flowing to the cathode and the hydrogen ions arriving from the membrane to form water.

In comparison with other types of fuel cells, the PEMFC has much better energy density parameters. One of its characteristics is the fact that its operating temperature strongly depends on the material of the membrane. When the widely used Nafion® is used, the operating temperature is lower, while in the case of PolyBenzImidazole it is higher, sometimes exceeding 200 °C.

Parameters:

• Type of electrolyte: proton-permeable membrane
• Operational temperature: 70°C-220°C
• Electric efficiency: 50%-70%

Reactions:

• On the anode: 2H₂ => 4H⁺ + 4e^-
• On the cahode: O₂ + 4H⁺ + 4e^- => 2H₂O
• The complete reaction: 2H₂ + O₂ => 2H₂O

Advantages:

• Efficient
• Cheap to produce due to the solid electrolyte
• Because of the solid electrolyte it is not sensitive to gravity
• Quick starting
• Long lifetime

Disadvantages:

• Complicated regulation (the electrolyte must be hydrated)
• Due to the low operating temperature the efficiency of heat utilization is low

Areas of use:

• Vehicle industry
• Arms industry
• Portable current sources
• Power plants

Related links

1. Fuel Cell Basics
2. Wikipedia