Bipolar plates in water electrolysis stacks: understanding basics and electrochemical aspects impacting the energy efficiency during operation

This tutorial review aims at presenting the concept of electrolysis with a bipolar electrode stack reactor. This design approach is commonly used industrially both for alkaline and PEM water electrolysis for hydrogen production. The goal here is notably to present and discuss the concept of shunt, parasitic and reverse currents, and to show how they affect the faradaic and the energy efficiencies of the electrolysis. These electrolyser design issues largely explain the difficulty to build very large industrial electrolyser plant which are necessary to produce hydrogen at the gigawatt level.