At the heart of a PEM fuel cell, there is a polymer membrane that has some unique capabilities. It is impermeable to gases, but it conducts protons (hence the name, proton exchange membrane). At the interface between the porous electrode and the polymer membrane, there is a layer with catalyst particles, typically platinum supported on carbon electro-chemical reactions happen at the surface of the catalyst at the interface between the electrolyte and the membrane.
Hydrogen, which is fed on one side of the membrane, splits into its primary constituents – protons and electrons. Protons travel through the membrane, whereas the electrons travel through electrically conductive electrodes, through the outside circuit where they perform useful work and come back to the other side of the membrane. At the catalyst sites between the membrane and the other electrode they meet with the protons that went through the membrane and oxygen that is fed on that side of the membrane.
As with the other cell types, it is necessary to stack SOFCs to increase the voltage and produce power. Since there are no liquid components, the SOFC can be cast into flexible shapes: tubular or planar. Development work for cells operating at 1000°C is focused on increasing the mechanical resistance of the cell materials to alleviate the impact of thermal mismatch and to develop techniques that will decrease interfacial changes of the various material layers during thin film cell fabrication.
Fuel cell technology offers many potential benefits as a distributed generation system. They are small and modular and capital costs are relatively insensitive to scale. This makes them ideal candidates for a diverse amount of applications where they can be matched to meet specific load requirements. The systems are unobtrusive with very low noise levels and have negligible air emissions.
These qualities enable them to be placed close to the source of power demand. Fuel cells also offer higher efficiencies than conventional plants.