A comprehensive review on PEM water electrolysis

► Water electrolysis is a key alternative to store energy from renewables. ► PEM electrolysis provides a sustainable solution for the production of hydrogen. ► Overview of the scientific and technological achievements in PEM electrolysis. ► PEM electrolysis has many challenges there are still unexplored. ► Clearly set the state-of-the-art for the PEM electrolysis technology.