Fuel cell startup from freezing temperatures is a requirement for automotive applications as many countries experience cold climate. It has been shown at Ballard Power Systems that an optimum MEA water content is necessary at startup in order to achieve fast freeze startup with no performance loss. In this paper we present stack models and designs for obtaining an appropriate MEA water content at startup by maximizing water migration from MEA to plate channels due to temperature gradients during natural cooling. Using this concept no external power is needed after fuel cell shut down from wet operation to achieve the intended MEA water content at startup. Experimental results for the MEA water content along the stack after shut down and natural cooling and for the stack performance during startup from freezing temperatures are presented for the new stack design.

Proton exchange membrane fuel cells (PEMFCs) continue to face cost and durability challenges which need to be addressed before their large scale commercialization. The PEM is an essential component of the fuel cell stack and its durability is thus a critical factor for the overall fuel cell reliability. Significant membrane degradation leads to the development of internal transfer leaks and cell short circuiting irreversibly affecting the fuel cell's functionality. In this study, perfluorosulfonic acid (PFSA) membranes were investigated for the effects of operating temperature and relative humidity on membrane durability using an open circuit voltage (OCV) accelerated stress test. The response surface methodology (RSM) was used to evaluate and optimize the effects of the operating temperature and humidity. As a result, the optimum fuel cell operational region was mapped and suggested as an alternative approach to maintain membrane durability without modifying membrane materials. The mapping could provide valuable guidelines for PEMFC designers and system engineers to optimize the operating conditions during idling to achieve a targeted membrane lifetime.