The PEM electrolyzer is superior to the alkaline as well as the solid oxide electrolyzers when it comes to rate capability and practical footprint. The cell owes its attractive properties to the combination of a good oxygen reduction catalyst and a durable and highly conductive membrane. The story could end here and often it does, but it is important to realize that there is also a severe limitation to the large-scale roll-out of this system. It relies on platinum group metals for catalysts and in most cases also noble metal coatings of cell components to limit the contact resistance in the acidic environment.

The noble metal issue (cost and availability) and the prospects for replacement of iridium oxide as oxygen catalyst are discussed. Platinum replacement is an active field within PEM fuel cell research. Why is that not the case to a similar extent for PEM electrolyzers? Finally, an alternative route to electrolyzers with rate capability like the PEM electrolyzers, but without the use of noble metals is suggested.