PEM electrolyzer, also known as proton exchange membrane electrolyzer, is a kind of equipment that uses electrolysis process to decompose water into hydrogen and oxygen. It consists of electrolyte membrane, usually made of polymer material, which allows protons to pass through and prevents electrons from passing through. When current is applied to the electrolytic cell, water molecules are dissociated into hydrogen ions (protons) and oxygen ions. Protons migrate through the membrane to the cathode, where they combine with electrons to form hydrogen. Oxygen ions migrate to the anode, where they combine with electrons to form oxygen.