The polymer electrolyte membrane pl

The polymer electrolyte membrane plays a critical and complex role in fuel cells. Its proton conducting capabilities define the electrical performance of the fuel cell on most of its operating range. Said capabilities are, in turn, tightly dependent upon the membrane’s water content. It is also responsible for a great deal of complexity at the system level where humidifiers and other water management devices are needed. One of the challenges in current MEA development is hence to design polymers with good resistance to mechanical stress and high conductivity at low water content. Inside the membrane, water exists in two forms: 1. Attached to protons, forming hydronium ions H3O+, which are transported from the anode to the cathode via electro-osmotic drag, and 2. In an unbound form transported between the electrodes via diffusion, usually from the cathode to the anode (back diffusion) due to the accumulation of product water at the cathode.