Chapter 3. Proton Exchange Membrane Water Electrolysers: Materials, Construction and Performance

Development of perfluorinated sulphonated acids (PFSAs) polymer electrolyte membranes brought about an important revolution in the design of electrolysis technology. Although originally targeted to the brine electrolysis process, it has found an irreplaceable position in a number of different technologies including energy conversion technologies utilising hydrogen. Although PFSA-based proton exchange membrane (PEM) fuel cells (FCs) are quite well established, the use of PEM in water electrolysis (WE) is an emerging technology. This chapter provides a review on the currently accepted state-of-the-art materials and components used in PEMWE, as well as introducing the main challenges and outlooks to their future solutions documented on selected current trials. Although a significant amount of information on PEMWE process can be derived from PEMFC technology, many questions remain, due to the fundamental differences in these two technologies. These include more extreme electrode potentials, caused predominantly by the sluggish oxygen evolution reaction (OER) kinetics and use of water acting as a reactant. These two aspects result in greater demands on the construction materials, which are significantly different from PEMFC technology. Individual components will be discussed starting from the catalysts and polymer electrolytes used and continuing to the single electrode, to the cell and cell stack construction.