PEMFC

The Proton Exchange Membrane (PEM) fuel cell uses a thin, permeable polymeric membrane as the electrolyte. The membrane is very small and light and in order to catalyse the reaction, platinum electrodes are used on either side of the membrane. Within the PEM fuel cell unit, hydrogen molecules are supplied at the anode and split in to hydrogen protons and electrons. The protons pass across the polymeric membrane to the cathode while the electrons are pushed round an external circuit in order to produce electricity. Oxygen (in the form of air) is supplied to the cathode and combines with the hydrogen ions to produce water.

SOFC

Solid oxide fuel cells (SOFCs) have grown in recognition as a viable high temperature fuel cell technology. There is no liquid electrolyte with its attendant material corrosion and electrolyte management problems. The operating temperature of >600C allows internal reforming, promotes rapid kinetics with non precious materials, and produces high quality by product heat for cogeneration or for use in a bottoming cycle, similar to the MCFC. The development of suitable low cost materials and the low cost fabrication of ceramic structures are presently the key technical challenges facing SOFCs.

MCFC

The MCFC is often referred to as a second generation fuel cell because it is expected to reach commercialization after PEMFCs. MCFCs differ in many respects from PAFCs because of their higher operating temperature (650 °C) and the nature of the electrolyte. The higher operating temperature of MCFCs provides the opportunity for achieving higher overall system efficiencies and greater flexibility in the use of fuels.