Most fuel cell batteries use Platinum as a catalyst in order to accelerate the chemical reactions which occur inside them. This presents one of the major problems in this field of electrical energy production, as Platinum is a rare metal and is also expensive. Two groups of researchers at the faculties of Science and Applied Sciences at the University of Liège are attempting, in two different ways, to greatly reduce the quantity of Platinum required.

A fuel cell battery is an electro-chemical device that reproduces the opposite phenomenon to the hydrolysis of water. The latter is an experiment that we have often carried out as children in our parents’ kitchen: when two electrodes are placed in a glass of water and a continuous current is passed through them one releases hydrogen and the other releases oxygen. The inverse phenomenon was noticed at the beginning of the 19th century: if hydrogen is insufflated onto one electrode and oxygen onto the other, a potential difference between the two electrodes can be seen.

A fuel cell battery is so-named because it has the same components as an ordinary battery: an oxidising agent and a reducing agent separated by an electrolyte. But in an ordinary battery, the oxidising and reducing agents are slowly used up. This is not the case with a fuel cell battery because they are continuously supplied to the battery. This is why the term« fuel cell» is used.

The device and the chemical reactions at work within it are very simple. The battery is composed of two electrodes (see illustration) separated by an electrolyte. An electrode (the anode) is fuelled by a combustible fuel, often hydrogen, but not necessarily: this could also be methanol or natural gas for example. The other electrode, (the cathode) is supplied by an oxidising agent, dioxygene (O₂), the electrolyte has a very important function: it must ensure that ions are conducted (most often H⁺) between the two compartments, but cannot conduct the electrons (e^-). These electrons which form the current pass through an exterior circuit. At the cathode, the ions, the e- and the oxygen recombine to form water. This reaction is, however, too slow under normal conditions. To accelerate this reaction, it is necessary to place a catalyst on the electrodes. In general, this catalyst is platinum, a metal which is rare and expensive. This is one of the major problems with most fuel cell batteries and is the reason why much research is being carried out to try to replace platinum or reduce the quantity thereof.

We therefore have a fuel, hydrogen for example, which is directly transformed into an electric current. In other words, the fuel cell battery is a device that makes possible the transition from chemical energy to electrical energy. In this way it is possible to avoid the stages of combustion, heat formation and transformation of heat into electricity as in a typical power station. There is therefore only one transformation instead of three (in a typical thermal power station, the chemical energy is first transformed into heat, the heat into mechanical energy then the mechanical energy is transformed into electricity).