The fuel cell works as follows:
- On the anode side (-), an oxidation reaction takes electrons from a fuel.
- On the cathode side (+), a reduction reaction allows an oxidant to capture electrons.
- The electrons follow a separate path and deliver an exploitable current.
There are several types of fuel (ethanol, methanol) but it is mainly dihydrogen that is used. This is known as a "hydrogen fuel cell". The oxidant is always the oxygen of the air (O2).
The hydrogen fuel cell is considered a clean energy source. It consumes hydrogen and oxygen, two elements that are abundant on Earth. In addition, the production of electricity from such a battery only emits water (H2O). However, there are still some negative points that need to be resolved before considering scaling up:
- Platinum is used as a catalyst. It is a rare and polluting metal.
- As much as the hydrogen element (H) is abundant, so much the dihydrogen (H2) is not. It must therefore be produced upstream, for example by electrolysis. This production consumes energy. The energy gain of the hydrogen fuel cell is reduced accordingly.
- Once H2 is produced, it must be transported and stored. Dihydrogen is "extremely flammable" (remember the Hindenburg accident) and it takes a lot of energy to compress it in the gaseous or liquid state (at -250 ° C).
It remains a promising source of energy and many research projects are trying to solve or get around these problems.