The technology takes its name from the fact that, in the process of electrolysis hydrogen ions H+ (protons) act as charge carrier. The first electrolyzer of this type has been developed by General Electric company. Fig.x presents a schematic view of a PEM electrolyser. During operation water is introduced at the anode and split into oxygen and hydrogen ions\cite{GRIGORIEV_2006}. The latter migrate through a solid membrane to the cathode where hydrogen molecules are formed. The half-reactions are following:
Anode: