How a Fuel Cell Works

A single fuel cell consists of a membrane electrode assembly and two flow field plates. Single cells are combined into a fuel cell stack to produce the desired level of electrical power.
Each membrane electrode assembly consists of two electrodes (anode and cathode) with a thin layer of catalyst, bonded to either side of a proton exchange membrane (PEM).

Gases (hydrogen and air) are supplied to the electrodes on either side of the PEM through channels formed in the flow field plates. Hydrogen flows through the channels to the anode where the platinum catalyst promotes its separation into protons and electrons. On the opposite side of the PEM, air flows through the channels to the cathode where oxygen in the air attracts the hydrogen protons through the PEM. The electrons are captured as useful electricity through an external circuit and combine with the protons and oxygen to produce water vapor on the cathode side.