Proton Exchange Membrane Fuel Cell

The Proton Exchange Membrane fuel cell, sometimes referred to as the Polymer Electrolyte Membrane fuel cell, is the chosen form for use in automotive applications.

Key   A. Hydrogen flow field

B. Oxygen flow field

C. Hydrogen

D. Oxygen (in air)

E. Backing layers

F. Anode

G. PEM (the electrolyte)

H. Cathode

J. Unused Hydrogen

K. Water

Process Hydrogen is passed through field flow plates to the anode whilst oxygen is similarly directed to the cathode. A platinum catalyst at the anode splits the hydrogen into protons (hydrogen ions) and negatively charged electrons. The electolyte (PEM) only allows the protons to pass through it directly to the cathode. The negatively charged electrons are forced to travel via a separate circuit to the cathode – hence generating an electrical current.

The energy from a single fuel cell is relatively small which means that multiple fuel cells must be used together before it is practical to power a vehicle. Fuel cells placed together are known as a ‘stack’.      

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