Production of hydrogen through electrolysis

In this review article we report on the fundamentals and the achieved technical status of the production of "green" hydrogen by water electrolysis. For this sustainable production of hydrogen, only purified water and renewable electrical energy are needed. However, due to the great stability of the water molecule, the energy demand of electrolysis is very high. We show that there are already three technically available technologies (alkaline, PEM and high-temperature electrolysis), each with specific advantages and disadvantages. Future developments focus on reducing the investment for electrolysis plants as well as on decreasing the losses in water splitting, for example through alkaline membrane electrolysis with an elegant combination of the properties of alkaline and PEM electrolysis.