What is the function of the membrane in a Polymer Electrolyte Membrane (PEM) electrolyzer?

The function of the membrane in a Polymer Electrolyte Membrane (PEM) electrolyzer is twofold: to act as a selective proton conductor and to provide a physical barrier separating the hydrogen and oxygen gases produced at the cathode and anode, respectively. A PEM electrolyzer uses a solid polymer electrolyte membrane, typically made of a perfluorosulfonic acid polymer like Nafion, to facilitate the movement of protons (H+) from the anode to the cathode. At the anode, water is oxidized, producing oxygen gas, protons, and electrons. The protons migrate through the membrane, while the electrons travel through an external circuit. At the cathode, the protons and electrons recombine to form hydrogen gas. The membrane is designed to be highly conductive to protons, allowing them to pass through easily, while being impermeable to electrons, preventing short-circuiting of the cell. Crucially, the membrane also prevents the mixing of hydrogen and oxygen gases, which would create a highly explosive mixture. By selectively allowing proton transport and physically separating the product gases, the membrane ensures efficient and safe operation of the PEM electrolyzer.