Fuel cell principle
Fuel cells are electrochemical energy converters which are continuously supplied with fuel.
The 2H2 + O2 → 2H2O reaction was recreated in 1838 by C. F. Schönbein when he constructed a simple fuel cell.
Today, technical fuel cells use this reaction to produce electrical energy. PEM fuel cells use hydrogen as an energy source and reach an electrical efficiency of around 50%. The fuel gas (H2) is catalytically oxidized at the anode, resulting in the production of electrons and protons. The protons permeate through the PEM (proton exchange membrane) into the chamber with the oxidant (O2 from the air). The electrons are diverted via a bipolar plate and flow to the electrical consumer, which is usually a battery.
At the cathode, the oxidant (O2) gains electrons and is reduced to anions, which immediately react with the hydrogen ions (protons) to form water. This water is released into the surroundings as steam