Proton Exchange Membrane Water Electrolysis

Proton exchange membrane (PEM) water electrolysis is considered one of the most promising technologies to produce hydrogen with a high degree of purity from renewable energy resources such as wind, photovoltaic and hydropower. The process is characterized by high efficiencies and elevated current densities at moderate temperatures. Compressed hydrogen can be directly obtained from the electrolyser at an increased level of safety. However, PEM water electrolysis systems are characterised by high cost, which is mainly due to the use of noble metal catalysts, perfluorinated membranes, and titanium bipolar plates. Challenging aspects include dealing with the overpotential for the oxygen evolution process, and the ohmic contribution of the polymer electrolyte membrane resistance at high current densities. In addition, mechanical, chemical, and electrochemical stability play an important role. The aim of the present chapter is to review the status of PEM electrolysis and to make a comparison with competing technologies. The main perspective for these systems is a suitable integration with renewable power sources for decentralised hydrogen production.