Analysis of the influence of temperature and gas humidity on the performance stability of polymer electrolyte membrane fuel cells

Adequate water management represents one of the main challenges in the design and operation of polymer electrolyte membrane fuel cells. In this work, the influence of inlet gas humidification on cell performance is investigated by in-situ current density measurements obtained using the segmented cell approach. Particular attention is paid to the combined effect of cell temperature and relative humidity of the anode and cathode feed streams. When operated at 80 degrees C and low humidity conditions, the cell is seen to undergo a severe voltage decline that is not observed at 60 degrees C. The analysis shows that the variation with temperature of the water uptake rate of the gaseous streams plays a key role in determining the observed differences in performance stability. In the case of 60 degrees C operation, the water uptake rate of the cathode stream at 50% inlet relative humidity is roughly 30% of its value at 80 degrees C at the same humidification level, resulting in a significantly lower drying capacity. A simple balance of water model, able to explain the observed cell behavior, is finally presented and discussed.This work has been partially supported by the European Union's Seventh Framework Programme (FP7/2007-20013) for Fuel Cell and Hydrogen Joint Technology Initiative under grants no 303446 and 325239, and by Project ENE2011-24574 of the Spanish Ministerio de Economía y Competitividad. Authors would also like to thank H. Sander at DLR and P. García-Ibarra at the Dept. de Física Matemática y de Fluidos (UNED) for helpful suggestions and discussions