Fuel cells combine hydrogen and oxygen, separated by a proton-conductive membrane impermeable to gas, which results in the generation of energy and production of water. Therefore, fuel cells represent an optimum method of directly converting chemical energy to electrical energy and heat in an electrochemical process. Fuel cells are exceptionally efficient because there are no intermediate steps.
Hydrogen is an ideal supplier of energy because it has more than three times the energy content of all other fossil fuels such as wood, coal or oil. Besides, when hydrogen is burned, only water is formed and no harmful greenhouse gases. If it were possible to produce hydrogen by water splitting via solar energy, wind or nuclear power or renewable raw materials, then this would be conducive to reducing global warming. Moreover, the fossil energy sources, limited in their supply, could then serve as a raw material source for the chemical industry rather than being used as fuel to such an extent.
In principle, a fuel cell operates like a battery. However the cell will supply electricity as long as fuel is supplied, for example in the form of hydrogen or methanol. A fuel cell consists of two electrodes, one cathode and one anode, separated by an electrolyte. The purpose of the electrolyte is to control the spontaneous combustion of hydrogen and oxygen, known as a detonating gas explosion. In polymer electrolyte membrane fuel cells (PEMFC), the electrolyte is replaced by a proton-conductive membrane impermeable to hydrogen and oxygen.
Hydrogen (H2) and air or oxygen (O2) flow over the electrode and are converted into water (H2O) and heat while generating energy. Hydrogen is routed to the anode where it splits into one proton and electrons (e) on the catalyst layer. The proton (H+) passes through the completely gas-tight membrane. The electrons, in the form of useful electric energy, are routed back to the cathode via a consumer. On the second catalyst layer on the cathode side, the proton reacts with the oxygen from the air to form water, the only by-product.