Schatz Energy Research Center - Education - Resources

How a Proton Exchange Membrane Fuel Cell Works

This animation shows the process that goes on inside an individual fuel cell. The red Hs represent hydrogen molecules (H2) from a hydrogen storage tank. The orange H+ represents a hydrogen ion after its electron is removed. The yellow e- represents an electron moving through a circuit to do work (like lighting a light bulb or powering a car). The green Os represent an oxygen molecule (O2) from the air, and the blue drops at the end are for pure water- the only byproduct of hydrogen power.

An animation details how a fuel cell functions. On the left side, hydrogen molecules are seen entering the fuell cell where they encounter a catalyst, which strips them of an electron before the hydrogen atoms pass through to the proton exchange membrane. Meanwhile, oxygen is flowing in from the upper-right portion of the animation and the electrons, from the Hydrogen atoms, continue their path to the bottom of the animation, representing the production of usable electricity. Eventually the electrons, hydrogen atoms and oxygen are recombined and exit the right side of the animation as water, the only exhaust from hydrogen power.

To produce power in large amounts, fuel cells are combined into a fuel cell stack. The image above shows a fuel cell stack composed of 36 cells.