Potentiostatic start-up of PEMFCs from subzero temperatures

Potentiostatic start-up of a proton exchange membrane fuel cell (PEMFC) from subfreezing temperatures is explored in this work. Taking advantage of hydration of membrane and rising cell temperature, potentiostatic start-up features a drastic increase in current density in the course of a cold start, thus leading to substantially more heat generation and a more rapid cell warmup. It is noted that potentiostatic start-up is more advantageous over its galvanostatic counterpart only when the membrane is dry prior to a cold start with sufficient gas purge. In addition, it is found that lowering the cell thermal mass significantly improves the performance of potentiostatic start-up. Minimizing the heat loss from end plates to the ambient is less critical for start-up processes of short duration. Finally, numerical results indicate that it is possible to achieve a self-start from -30°C in ∼50 s under realistic conditions using the potentiostatic method. While potentiostatic start-up cannot be used directly for fuel cell stacks, it is a fundamental problem representing innovative current-ramping strategies.